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Engine Controls - 6.6L (LB7) (Troubleshooting & Diagnosis: Other GMC Sierra 3500

Testing & Diagnostics 5 illustrations ~7427 words

Before Using This Section

Before using this section, you should have performed the Diagnostic System Check-Engine Controls and determined that the following criteria

  1. The control module and the malfunction indicator lamp (MIL) are operating correctly.
  2. There are no diagnostic trouble codes (DTCs) stored, or a DTC exists but without MIL.

Several of the following symptom procedures call for a careful visual and physical inspection. The visual and physical inspection is very important. The inspection can lead to correcting a problem without further inspection which may save valuable time.

Verify Customer's Concern

Locate the correct symptom table. Inspect the items indicated under that symptom from the following symptom tables

  1. «Intermittent Conditions»(ref-184194-S13353318862005082200000)
  2. «Hard Start»(ref-184194-S35105983852005082200000)
  3. «Surges/Chuggles»(ref-184194-S08952423182005082200000)
  4. «Lack of Power, Sluggishness, or Sponginess»(ref-184194-S03248165952005082200000)
  5. «Fuel Knock/Combustion Noise»(ref-184194-S19813613522005082200000)
  6. «Hesitation, Sag, Stumble»(ref-184194-S08607212822005082200000)
  7. «Cuts Out, Misses»(ref-184194-S17592601402005082200000)
  8. «Poor Fuel Economy»(ref-184194-S20786866832005082200000)
  9. «Rough, Unstable, or Incorrect Idle and Stalling»(ref-184194-S09795850982005082200000)
  10. «Excessive Smoke (Excessive Black Smoke)»(ref-184194-S11065240152005082200000) or «Excessive Smoke (Excessive Gray or Blue Smoke)»(ref-184194-S16966359022005082200000) or «Excessive Smoke (Excessive White Smoke)»(ref-184194-S09300126562005082200000)

Intermittent Conditions

An intermittent condition may or may not turn on the malfunction indicator lamp (MIL) or store a diagnostic trouble code (DTC).

Intermittent Malfunction Indicator Lamp (MIL)

The following can cause an intermittent MIL and no DTCs

  1. Electrical system interference caused by a malfunctioning relay, ECM driven solenoid, or switch. The electrical component can cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating.
  2. The improper installation of electrical devices; such as lights, 2-way radios, electric motors, etc.
  3. The MIL circuit intermittently shorted to ground.
  4. Poor ECM grounds

Hard Start

InspectionAction
DEFINITION: The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies.
Preliminary InspectionRefer to Symptoms - Engine Controls . Ensure the driver is using the correct starting procedure.
Sensor InspectionInspect the engine coolant temperature (ECT) sensor. Use the scan tool to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself. Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System InspectionInspect the fuel pressure regulator 12-volt circuit for an intermittent short to ground. Observe the FRP Command percent while cranking. A range of 85-95 percent indicates a possible short to ground condition. Start the engine and command the fuel pressure to 160 MPa with a scan tool. If the actual fuel pressure does not reach 160 MPA, perform the Fuel System Diagnosis - High Pressure Side . Inspect the fuel supply to the fuel injection pump. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for air in the fuel system. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for external fuel leaks. Refer to Fuel Leaks (Outside of Engine) or Fuel Leaks (Inside of Engine) . Inspect for high engine oil level. Refer to Fuel in Engine Oil in Engine Mechanical - 6.6L. Inspect the fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) . At idle observe the FRP Regulator Fuel Flow Command parameter with a scan tool. If the FRP Regulator Fuel Flow Command is more than 2700 mm 3 , perform the Fuel System Diagnosis - High Pressure Side . Inspect the fuel tank cap vent for proper operation.
Electrical System InspectionInspect the glow plug system for proper operation. Refer to Glow Plug System Diagnosis . Inspect for a slow cranking speed. Refer to Symptoms - Engine Electrical in Engine Electrical.
Air Intake System InspectionInspect the air cleaner and air intake ducts for a restrictions or leaks. Inspect for a restriction in turbocharger inlet duct. Inspect for a restriction or a leak in the intake manifolds.
Exhaust System InspectionInspect the exhaust system for a possible restriction. Refer to Restricted Exhaust in Engine Exhaust.
Engine Mechanical InspectionInspect the engine for the following conditions: Improper valve timing Bent pushrods Worn rocker arms-Refer to Valve Rocker Arm and Shaft Cleaning and Inspection in Engine Mechanical - 6.6L. Low engine compression-Refer to Engine Compression Test in Engine Mechanical - 6.6L. Broken or weak valve springs Worn camshaft lobes-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical - 6.6L.
Additional InspectionInspect for an intermittent CKP signal. Refer to Intermittent Conditions . Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List . Inspect the Service Bulletins for control module software updates.

Hard Start

Surges/Chuggles

InspectionAction
DEFINITION: The engine has a power variation under a steady throttle or cruise. The vehicle seems to speed up and slow down with no change in the accelerator pedal.
Preliminary InspectionRefer to Symptoms - Engine Controls . Ensure the driver understands the torque converter clutch (TCC) operation. Ensure the driver understands the A/C compressor operation. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List . Use the scan tool to ensure the vehicle speed sensor (VSS) reading matches the speedometer. This excludes vehicles with electronic transmissions where some variation between VSS and the speedometer is normal.
Sensor InspectionTurn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Test for an intermittent FRP sensor signal by wiggling the harness between the sensor and the ECM with the ignition ON and the engine OFF, while monitoring the parameter with a scan tool. Observe the FRP sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor exists. Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System InspectionInspect the fuel supply system vacuum while the problem exists. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for a sticking Fuel Pressure Regulator. The symptom for this condition will be an idle surge of at least 100 RPM. This surge will be from 50 RPM above Desired Idle Speed to 50 RPM below Desired Idle Speed. Refer to Fuel System Diagnosis - High Pressure Side .
Additional InspectionInspect the fuel injection control circuits between the engine control module (ECM) and the fuel injection control module (FICM) for a short to a 5-volt reference circuit. Inspect the control module grounds for being clean, tight, and in their proper locations. Inspect the generator output voltage. Repair if less than 9 volts or more than 16 volts. Inspect the vacuum lines for restrictions, leaks, or improper connections. Inspect the torque converter clutch (TCC) operation.

Surges/Chuggles

Lack of Power, Sluggishness, or Sponginess

ChecksAction
DEFINITION: The engine delivers less than expected power. There is little or no increase in speed when partially applying the accelerator pedal.
Preliminary ChecksRefer to Symptoms - Engine Controls . Inspect for auxiliary fuel filters. Refer to Fuel Injection Line Routing Diagram for proper fuel tilter locations. Aftermarket fuel filters may restrict fuel flow. Compare the vehicle with a similar unit. Ensure the vehicle has an actual problem. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List . Remove the air filter and check for dirt, or for air ducts being plugged or leaking. Repair or replace as necessary. Inspect for a proper transmission operation. Inspect the engine oil level and quality.
Sensor InspectionObserve the fuel rail pressure (FRP) sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor exists. Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System ChecksInspect the fuel supply to the fuel injection pump. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Observe the actual vs desired fuel rail pressure with a scan tool, with the engine idling. Start the engine and command the fuel pressure to 160 MPa with a scan tool. If the actual fuel pressure does not reach 160 MPA, go to Fuel System Diagnosis - High Pressure Side . Inspect the engine speed signal circuit for high resistance. Inspect for restricted or plugged fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) .
Exhaust System ChecksInspect the exhaust system for a possible restriction. Refer to Restricted Exhaust in Engine Exhaust.
Air Intake System ChecksInspect for an air leak or restriction in the air inlet ducts or the intake manifold. Refer to DTC P0234 (Federal RPO FE9, NG1) or DTC P0234 (California RPO YF5, NE1, and VCL) . Inspect for an air leak or restriction in the charge air cooler with a J 46091 Charge Air Cooler Tester. Inspect for a worn or damaged turbo charger turbine wheel, shaft or compressor wheel. Inspect for a skewed mass air flow (MAF) sensor. Refer to Diagnostic Aids in DTC P0101 .
Engine Mechanical CheckInspect the engine for the following: Low compression Improper valve timing Improper or worn camshaft Refer to Engine Compression Test in Engine Mechanical.
Additional ChecksInspect the control module grounds for being clean, tight, and in their proper location. Inspect the torque converter clutch (TCC) operation. Inspect the air conditioning system for proper operation. Refer to Diagnostic System Check - HVAC Systems - Automatic or Symptoms - HVAC Systems - Manual in HVAC. Inspect the generator output voltage. Refer to Charging System Test (CS/AD/SI Generators) in Engine Electrical.

Lack of Power, Sluggishness, or Sponginess

Hesitation, Sag, Stumble

InspectionAction
DEFINITION: The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur at any vehicle speed. The condition is usually most severe when trying to make the vehicle move from a stop. If severe enough, the condition may cause the engine to stall.
Preliminary InspectionRefer to Symptoms - Engine Controls .
Fuel System InspectionInspect the fuel supply system vacuum. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for water contamination in the fuel. Refer to Contaminants-in-Fuel Diagnosis . Perform the Fuel Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) . Inspect for high fuel supply system vacuum after a cold start or during moderate or full throttle acceleration. If the vacuum jumps above specification, there is a restriction in the fuel system.
Sensor InspectionTurn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Test for an intermittent FRP sensor signal by wiggling the harness between the sensor and the engine control module (ECM) with the ignition ON and the engine OFF, while monitoring the parameter with a scan tool. Observe the FRP sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor exists. Inspect for an intermittent crankshaft position (CKP) sensor signal. Refer to Intermittent Conditions . Inspect the CKP sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Additional InspectionReview the service bulletins for control module software updates. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List . Inspect the generator output voltage. Refer to Charging System Test (CS/AD/SI Generators) in Engine Electrical.

Hesitation, Sag, Stumble

Cuts Out, Misses

InspectionAction
DEFINITION: A constant jerking that follows the engine speed, usually more pronounced as the engine load increases which is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle, low speed, or hard acceleration for the fuel starvation that can cause the engine to cut-out.
Preliminary InspectionRefer to Symptoms - Engine Controls . Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List .
Sensor InspectionObserve the fuel rail pressure (FRP) sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor exists. Inspect for an intermittent crankshaft position (CKP) sensor signal. Refer to Intermittent Conditions . Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Engine Mechanical InspectionPerform the Engine Compression Test. Refer to Engine Compression Test in Engine Mechanical - 6.6L. Inspect the engine for the following conditions: Improper valve timing Bent pushrods Worn rocker arms Worn camshaft lobes Broken or weak valve springs, refer to Symptoms - Engine Mechanical in Engine Mechanical - 6.6L. Inspect the intake and exhaust manifold passages for casting flash.
Fuel System InspectionInspect the fuel system for a plugged fuel filter, high vacuum, air in the fuel system, etc. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for water contamination in the fuel. Refer to Contaminants-in-Fuel Diagnosis . Inspect the fuel injectors for proper operation. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) .

Cuts Out, Misses

Poor Fuel Economy

InspectionAction
DEFINITION: Fuel economy, as measured by actual road tests and several tanks of fuel, is noticeably lower than expected. Also, the economy is noticeably lower than it was on this vehicle at one time, as previously shown by actual road tests.
Preliminary InspectionRefer to Symptoms - Engine Controls . Inspect the air filter for dirt or being plugged. Inspect for an air leak in the charge air cooler with a J 46091 Charge Air Cooler Tester. Inspect the vacuum hoses for splits, restrictions, and improper connections. Perform the Diagnostic System Check - Engine Controls . Inspect the air conditioning system for proper operation. Inspect the tires for correct air pressure. Inspect the driving habits of the owner. Are heavy loads being carried? Suggest to the owner to fill the fuel tank and inspect the fuel economy. Suggest to the driver to read the Important Facts on Fuel Economy in the Owner Manual.
Sensor InspectionObserve the fuel rail pressure (FRP) sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor concern exists. Inspect for an intermittent crankshaft position (CKP) sensor signal. Refer to Intermittent Conditions . Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System InspectionInspect the fuel type. Inspect the fuel system vacuum. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) .
Cooling System InspectionInspect the engine coolant level. Inspect the engine thermostats for always being open or for the wrong heat range. Refer to Thermostat Diagnosis in Engine Cooling.
Additional InspectionInspect the transmission for proper operation. Inspect the torque converter clutch (TCC) operation. When the TCC is commanded ON, a scan tool should indicate an RPM drop. Inspect the Service Bulletins for control module software updates. Inspect the brake for proper operation.

Poor Fuel Economy

Rough, Unstable, or Incorrect Idle and Stalling

InspectionAction
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine.
Preliminary InspectionRefer to Important Preliminary Inspection Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the vehicle for factory or aftermarket accessories that may contact the body and chassis. A grounding out condition may simulate a misfire or rough run concern. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List . Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Remove and inspect the air filter element for dirt or for being restricted. Refer to Air Cleaner Element Replacement . Replace as necessary.
Sensor InspectionTurn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Test for an intermittent FRP sensor signal by wiggling the harness between the sensor and the ECM with the ignition ON and the engine OFF, while monitoring the parameter with a scan tool. Observe the FRP sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor exists. Inspect for an intermittent crankshaft position (CKP) sensor signal. Refer to Intermittent Conditions . Inspect the CKP sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose. Inspect for proper crankcase ventilation.
Fuel System InspectionPerform the fuel injector balance test. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis (Pickup) or Fuel System Diagnosis (Cab Chassis) . Inspect for a restriction in the fuel return system. Refer to Fuel Return System Diagnosis . Inspect for a contaminated fuel condition. Refer to Contaminants-in-Fuel Diagnosis . Inspect for a sticking Fuel Pressure Regulator. The symptom for this condition will be an idle surge of at least 100 RPM. This surge will be from 50 RPM above Desired Idle Speed to 50 RPM below Desired Idle Speed. Refer to Fuel System Diagnosis - High Pressure Side .
Engine Mechanical InspectionInspect engine mechanical for the following: Inspect the cylinder compression. Refer to Engine Compression Test in Engine Mechanical - 6.6L. Sticking or leaking valves Worn camshaft lobes Valve timing Bent push rods Worn rocker arms Broken valve springs Excessive oil in the combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical - 6.6L. Inspect the following components for incorrect basic engine parts: Camshaft-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical - 6.6L. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical - 6.6L. Pistons, connecting rods, or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical - 6.6L.
Additional InspectionInspect the following components of the exhaust system for possible restrictions: The exhaust system for damaged or collapsed pipes The exhaust manifold for a collapsed inner wall The mufflers for heat distress or possible internal failure Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates that EMI is present. If a problem exists, inspect routing of high voltage components, such as fuel injector wiring, near the sensor circuits. Inspect the park neutral position (PNP) switch circuit. Inspect for a short to 5 volts on one of the fuel injector control circuit between the ECM and the FICM. Inspect for faulty motor mounts. Refer to Engine Mount Inspection in Engine Mechanical - 6.6L. Inspect the intake manifold and the exhaust manifold passages for casting flash.

Rough, Unstable, or Incorrect Idle and Stalling

Excessive Smoke (Excessive Black Smoke)

InspectionAction
DEFINITION: Black smoke under load, idle or start up hot or cold.
Preliminary InspectionRefer to Symptoms - Engine Controls . Ensure the customer has an actual problem. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List .
Fuel System InspectionObserve the actual vs. desired fuel rail pressure with a scan tool, with the engine running. Inspect the fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) .
Sensor InspectionInspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself. Inspect the glow plug system operation. Refer to Glow Plug System Diagnosis . Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Air Intake System InspectionInspect for a restriction in the air cleaner or the air intake ducts. Inspect for a restriction in the turbocharger charge air cooler. Inspect for a restriction in the intake manifold. Inspect for an air leak in the charge air cooler with a J 46091 Charge Air Cooler Tester. Inspect for an air leak in the air ducts between the turbocharger and the intake manifold.
Engine Mechanical InspectionInspect for incorrect basic engine parts such as the cam, the heads, the pistons, etc. Inspect for excessive oil entering the combustion chamber. Refer to Oil Consumption Diagnosis in Engine Mechanical - 6.6L.

Excessive Smoke (Excessive Black Smoke)

Excessive Smoke (Excessive Gray or Blue Smoke)

InspectionAction
DEFINITION: Gray or blue smoke under load, idle or start up hot or cold.
Preliminary InspectionsRefer to Symptoms - Engine Controls . Ensure the customer has an actual problem. Check the coolant level in the reservoir. White coolant smoke may be mistaken for blue/gray smoke. If the coolant level is low refer to Loss of Coolant in Engine Cooling. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List .
Fuel System InspectionObserve the actual vs. desired fuel rail pressure with a scan tool, with the engine running. Inspect the fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) .
Sensor InspectionInspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself. Inspect the glow plug system operation. Refer to Glow Plug System Diagnosis . Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Air Intake System InspectionInspect the air cleaner and the air intake ducts for restriction. Inspect for contamination of the mass air flow (MAF) sensor. Inspect for a restriction in the turbocharger charged air cooler. Inspect for a restriction in the intake manifold.
Engine Mechanical InspectionPerform a cylinder leakage test. Perform the engine compression test. Refer to Engine Compression Test in Engine Mechanical - 6.6L. Inspect for incorrect basic engine parts such as the cam, the heads, the pistons, piston rings, and valves. Inspect for excessive oil entering the combustion chamber. Refer to Oil Consumption Diagnosis in Engine Mechanical - 6.6L.
Turbocharger InspectionInspect for leaking seals in the turbocharger. A slight film on the intake side is normal.

Excessive Smoke (Excessive Gray or Blue Smoke)

Excessive Smoke (Excessive White Smoke)

InspectionAction
DEFINITION: White smoke under load, idle or start up hot or cold.
Preliminary InspectionRefer to Symptoms - Engine Controls . Ensure the customer has an actual problem. Check the coolant level in the reservoir. White coolant smoke may be mistaken for blue/gray smoke. If the coolant level is low refer to Loss of Coolant in Engine Cooling. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List .
Fuel System InspectionIf excessive smoke is present, inspect for a stuck open fuel injector by performing the following procedure: Remove the ignition 1 relay. Remove the glow plugs. Refer to Glow Plug Replacement - Bank 1 and Glow Plug Replacement - Bank 2 . IMPORTANT: Do not stand in front of the glow plug holes while cranking the engine. Crank the engine while observing the glow plug holes for fuel spray. Replace the fuel injectors for the cylinders that spray fuel. Inspect for contaminated oil or high oil level. Refer to Fuel in Engine Oil in Engine Mechanical - 6.6L. Inspect the fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 (with Automatic Transmission) or Fuel Injector Balance Test with Tech 2 (with Manual Transmission) .
Sensor InspectionInspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself. Inspect the glow plug system operation. Refer to Glow Plug System Diagnosis . Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.0-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Air Intake System InspectionInspect the air cleaner and the air intake ducts for restriction. Inspect for a restriction in the turbocharger charge air cooler. Inspect for a restriction in the intake manifold. Refer to Intake Manifold Cleaning and Inspection in Engine Mechanical - 6.6L. Inspect the intake air heater (IAH) for proper operation. Use a scan tool to command the IAH ON and OFF. Refer to DTC P0540 and DTC P0543 .
Engine Mechanical InspectionInspect for incorrect basic engine parts such as the cam, the heads, the pistons, etc. Inspect for coolant entering the combustion chamber.
IMPORTANT
Do not stand in front of the glow plug holes while cranking the engine.

Excessive Smoke (Excessive White Smoke)

Supply System

The fuel flows through a pre-filter screen in the tank and to the engine through the fuel supply lines. There is no lift pump in the fuel tanks or on the frame. The fuel passes through the base plate of the fuel injector control module (FICM) to cool the module. From the FICM the fuel flows to the fuel filter assembly, which combines a water separator, a prime pump and a filter element. Within the assembly, there is also a fuel heater. An integrated hand pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn to the supply pump from the primary fuel tank by the supply pump and delivered to the high-pressure pump.

High Pressure System

The much larger section of the pump assembly is the high-pressure fuel injection pump. The pump is engine-driven by the camshaft gear. From the high-pressure pump, the pressurized fuel flows to the left common fuel rail, then to the right common fuel rail. Each common fuel rail supplies one bank of four fuel injectors.

Return System

The Fuel Return System routes fuel from the fuel injectors and the fuel injection pump. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.

Scheme 453

Scheme 453: Fuel System Air Leak Check
Scheme 453: Fuel System Air Leak Check

Scheme 454

Scheme 454
Scheme 454
  1. Install the J 44638 Vacuum Gage to the fuel system service port on the right front side of the engine.
  2. Remove the air duct from the air cleaner assembly to the turbo inlet.
  3. Remove the generator for visibility of the fuel supply lines. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  4. Prime the fuel system until 10 psi is indicated on the J 44638 .
  5. Check for external fuel leaks between the fuel filter assembly and the fuel injection pump. If fuel is leaking externally, replace or repair the leaking component. If no external fuel leaks are found, go to step 6.
  6. Reprime the fuel system until 10 psi is indicated on the J 44638 . If the fuel pressure drops from 10 psi to 2 psi in less than 1 minute, go to step 24. If the fuel pressure drops from 10 psi to 2 psi in more than 1 minute, go to step 7.
  7. Disconnect the fuel supply line (2) at the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  8. Cap off the fuel supply pipe (2) on the engine with a 1/2 inch rubber plug (3) and clamp.
  9. Disconnect the fuel return line (1) at the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  10. Install a J 23738-A Mityvac on the fuel return pipe on the engine.
  11. Check the fuel system components on top of the engine for vacuum leaks. IMPORTANT: There is an orifice in the fuel injection pump between the fuel supply and fuel return systems. This will delay the vacuum being pulled from the fuel supply lines. Apply at least 25 inches Hg of vacuum to the fuel return pipe with the J 23738-A and wait more than 1 minute for the system to stabilize. Repeat the previous substep 6 times. Observe the J 23738-A . If the vacuum does not drop below 8 inches within 10 minutes, go to step 12. If the vacuum drops below 8 inches within 10 minutes, go to step 22.
  12. Reconnect the fuel supply line at the engine.
  13. Disconnect the chassis fuel line from the short fuel line between the fuel sender and the chassis fuel line in front of the fuel tank (1). Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  14. Plug the chassis fuel line (1) using a 1/2 inch rubber plug, and clamp the plug.
  15. Check the fuel system components on top of the engine for vacuum leaks. IMPORTANT: There is an orifice in the fuel injection pump between the fuel supply and fuel return systems. This will delay the vacuum being pulled from the fuel supply lines. Apply at least 25 inches Hg of vacuum to the fuel return pipe with the J 23738-A and wait more than 1 minute for the system to stabilize. Repeat the previous substep 10 times. Observe the J 23738-A . If the vacuum does not drop below 8 inches within 10 minutes, go to step 16. If the vacuum does drop below 8 inches within 10 minutes, inspect the O-ring sealing surfaces of the engine fuel supply line for damage and correct as necessary. If the sealing surfaces are not damaged, replace the chassis fuel lines and go to step 29.
  16. Reconnect the fuel line at the fuel tank and the fuel return line at the engine.
  17. Install a transparent hose between the fuel injection control module (FICM) outlet and the fuel filter inlet, with a vertical loop to observe the incoming fuel for air bubbles.
  18. Install the generator. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  19. Prime the fuel system 30 times to remove the air in the fuel system.
  20. Start and idle the engine.
  21. Observe the fuel in the transparent hose for air bubbles. If there are no air bubbles of any kind entering the transparent hose with the incoming fuel, the fuel suction system is OK. Go to step 29. If any air bubbles are entering the transparent hose with the incoming fuel, stop the engine and go to step 23.
  22. Check the fuel injection pump and the on-engine fuel suction system for air leakage. Disconnect the fuel outlet hose (2) from the outlet pipe (1) of the fuel filter assembly. Open the drain on the fuel filter assembly and drain the fuel into a suitable container. Close the drain. Install a J 23738-A on the outlet port (1) of the fuel filter assembly. Apply 15 inches Hg of vacuum to the fuel pipe and observe the J 23738-A . If the vacuum does not drop, connect the fuel supply line at the engine and go to the next substep. If the vacuum drops, repair the air leak between the fuel supply line fitting and the fuel filter assembly. Install a J 23738-A to the fuel outlet hose (2) from the fuel filter assembly. Remove the Air Intake Pipe. Refer to «Air Intake Pipe Replacement»(ref-184139-S39919690542005082200000) . Remove the supply hose (3) from the fuel injection pump (4) and plug the hose. Apply 15 inches Hg of vacuum and observe the reading. If the vacuum drops, repair the leak between the fuel filter assembly outlet and the fuel injection pump inlet. If the vacuum does not drop, go to the next substep. Disconnect the fuel injection pump return hose (1). Cap off the fuel return pipe on the fuel injection pump with a 1/2 inch rubber plug, and clamp the plug. Install a J 23738-A to the fuel inlet pipe of the fuel injection pump. Apply 20 inches of vacuum and observe the J 23738-A . If the vacuum drops, replace the fuel injection pump. Refer to «Fuel Injection Pump Replacement»(ref-184139-S15894787592005082200000) . Then go to step 29. If the vacuum does not drop, replace the fuel injection pump inlet supply hose (3). Then go to step 29.
  23. Check the fuel sender for air leakage. Remove the fuel tank. Refer to «Fuel Tank Replacement (Pickup)»(ref-184139-S25222812662005082200000) or «Fuel Tank Replacement (Cab/Chassis - Front)»(ref-184139-S15896634012005082200000) or «Fuel Tank Replacement (Cab/Chassis - Rear)»(ref-184139-S14458213192005082200000) . Remove the fuel sender from the fuel tank. Remove the strainer from the fuel sender and plug the bottom end of the pickup tube. Apply 15 inches Hg of vacuum to the upper end of the pickup tube and observe the J 23738-A . If the vacuum holds, inspect the O-ring sealing surfaces of the fuel sending unit and the chassis fuel line for damage and correct as necessary. If the sealing surfaces are not damaged, replace the fuel line between the chassis line and the fuel sending unit. Then go to Step 29. If the vacuum does not hold replace the fuel sender, reinstall the fuel tank, and go to step 29.
  24. Prime the fuel system 30 times or until fuel pressure is 10 psi to remove the air from the fuel system. Air will be forced out of the system within 2 minutes.
  25. Remove the hose from the fuel filter assembly outlet fitting and plug the hose.
  26. Verify that the J 44638 is installed.
  27. Remove the ignition 1 relay.
  28. Crank the engine 2-3 times in 15 second intervals and observe the J 44638 . If the indicates 5 inches Hg of vacuum or more, go to step 6. If the indicates less than 5 inches Hg of vacuum, replace the fuel injection pump. Refer to «Fuel Injection Pump Replacement»(ref-184139-S15894787592005082200000) . Then go to step 29.
  29. Remove the transparent hose if necessary and attach any disconnected components or fuel lines.
  30. Prime the fuel system 30 times to remove the air in the fuel hoses
  31. Clean any fuel spillage.
  32. Start the engine. If the engine starts and stalls, repeat step 30.
  33. Run the engine to check for fuel leakage.
  34. Verify that the customer concern is corrected. If the customer concern is not corrected, go to «Symptoms - Engine Controls»(ref-184194-S02322581032005082200000) .

The fuel flows through a pre-filter screen in the tank and to the engine through the fuel supply lines. There is no lift pump in the fuel tanks or on the frame. The fuel passes through the base plate of the fuel injector control module (FICM) to cool the module. From the FICM the fuel flows to the fuel filter assembly, which combines a water separator, a prime pump and a filter element. Within the assembly, there is also a fuel heater. An integrated hand pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn to the supply pump from the primary fuel tank by the supply pump and delivered to the high-pressure pump.

The much larger section of the pump assembly is the high-pressure fuel injection pump. The pump is engine-driven by the camshaft gear. From the high-pressure pump, the fuel flows through the junction block. The junction block routes pressurized fuel to both common fuel rails. Each common fuel rail supplies one bank of four fuel injectors.

The Fuel Return System routes fuel from the fuel injectors, the junction block, and the fuel injection pump. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.

Fuel System Air Leak Check

  1. Install the J 44638 Vacuum Gage to the fuel system service port on the right front side of the engine.
  2. Remove the air duct from the air cleaner assembly to the turbo inlet.
  3. Remove the generator for visibility of the fuel supply lines. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  4. Prime the fuel manager until 10 psi is indicated on the J 44638 .
  5. Check for external fuel leaks between the fuel filter/heater assembly and the fuel injection pump. If fuel is leaking externally, replace or repair the leaking component. If no external fuel leaks are found, go to step 6.
  6. Reprime the fuel system until 10 psi is indicated on the J 44638 . If the fuel pressure drops from 10 psi to 2 psi in less than 1 minute, go to step 23. If the fuel pressure drops from 10 psi to 2 psi in more than 1 minute, go to step 7.
  7. Disconnect the fuel supply line (2) at the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  8. Cap off the fuel supply pipe (2) on the engine with a 1/2 inch rubber plug (3) and clamp.
  9. Disconnect the fuel return line (1) at the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  10. Install a J 23738-A Mityvac on the fuel return pipe on the engine.
  11. Check the fuel system components on top of the engine for vacuum leaks. IMPORTANT: There is an orifice in the fuel injection pump between the fuel supply and fuel return systems. This will delay the vacuum being pulled from the fuel supply lines. Apply at least 25 inches Hg of vacuum to the fuel return pipe with the J 23738-A and wait more than 1 minute for the system to stabilize. Repeat previous substep 6 times. Observe the J 23738-A . If the vacuum does not drop below 8 inches within 10 minutes, go to step 12. If the vacuum drops below 8 inches within 10 minutes, go to step 18.
  12. Reconnect the fuel supply line and the return line at the engine.
  13. Install a transparent hose between the fuel injection control module (FICM) outlet and the fuel filter inlet, with a vertical loop to observe the incoming fuel for air bubbles.
  14. Install the generator. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  15. Prime the fuel system 30 times to remove the air from the fuel hoses.
  16. Start and run the engine.
  17. Observe the fuel in the transparent hose for air bubbles. If there are no air bubbles of any kind entering the transparent hose with the incoming fuel, the fuel suction system is OK. Go to step 28. If any air bubbles are entering the transparent hose with the incoming fuel, stop the engine and go to step 19.
  18. Check the fuel injection pump and the on-engine fuel suction system for air leakage. Disconnect the fuel outlet hose (2) from the outlet pipe (1) of the fuel filter assembly. Open the drain on the fuel filter assembly and drain the fuel into a suitable container. Close the drain. Install a J 23738-A on the outlet port (1) of the fuel filter assembly. Apply 15 inches Hg of vacuum to the fuel pipe and observe the J 23738-A . If the vacuum does not drop, connect the fuel supply line at the engine and go to the next substep. If the vacuum drops, repair the air leak between the fuel supply line fitting and the fuel filter assembly. Remove the J 23738-A from the outlet port (1) of the fuel filter assembly and install the J 23738-A to the fuel outlet hose (2). Remove the Air Intake Pipe. Refer to «Air Intake Pipe Replacement»(ref-184139-S39919690542005082200000) . Remove the supply hose (3) from the fuel injection pump (4) and plug the hose. Apply 15 inches Hg of vacuum and observe the reading. If the vacuum drops, repair the leak between the fuel filter assembly outlet and the fuel injection pump inlet. If the vacuum does not drop, go to the next substep. Disconnect the fuel injection pump return hose (1). Cap off the fuel return pipe on the fuel injection pump with a 5/16 inch rubber plug, and clamp the plug. Install a J 23738-A to the fuel inlet pipe of the fuel injection pump. Apply 20 inches of vacuum and observe the J 23738-A . If the vacuum drops, replace the fuel injection pump. Refer to «Fuel Injection Pump Replacement»(ref-184139-S15894787592005082200000) . Then go to step 28. If the vacuum does not drop, replace the fuel injection pump inlet supply hose (3). Then go to step 28.
  19. Check the fuel sender for air leakage. Remove the front fuel tank. Refer to «Fuel Tank Replacement (Pickup)»(ref-184139-S25222812662005082200000) or «Fuel Tank Replacement (Cab/Chassis - Front)»(ref-184139-S15896634012005082200000) or «Fuel Tank Replacement (Cab/Chassis - Rear)»(ref-184139-S14458213192005082200000) . Remove the fuel sender from the fuel tank. Remove the strainer from the fuel sender and plug the bottom end of the pickup tube. Apply 15 inches Hg of vacuum to the upper end of the pickup tube and observe the J 23738-A . If the vacuum holds, inspect the O-ring sealing surfaces of the fuel sending unit and the chassis fuel line for damage and correct as necessary. If the sealing surfaces are not damaged, replace the fuel line between the chassis line and the fuel sending unit. Then go to Step 20. If the vacuum does not hold replace the fuel sender, reinstall the fuel tank, and go to step 20.
  20. Prime the fuel system 30 times or until fuel pressure is 10 psi to remove the air from the fuel system. Air will be forced out of the system within 2 minutes.
  21. Start and run the engine.
  22. Observe the fuel for air bubbles. If there are no air bubbles of any kind entering the transparent hose with the incoming fuel, the fuel suction system is OK. Go to step 28. If any air bubbles are entering the transparent hose with the incoming fuel, stop the engine and go to step 8.
  23. Prime the fuel system 30 times or until fuel pressure is 10 psi to remove the air from the fuel system. Air will be forced out of the system within 2 minutes.
  24. Remove the hose from the fuel filter assembly outlet fitting and plug the hose.
  25. Verify that the J 44638 is installed.
  26. Remove the ignition 1 relay.
  27. Crank the engine 2-3 times in 15 second intervals and observe the J 44638 . If the J 44638 indicates 5 inches Hg of vacuum or more, go to step 28. If the J 44638 indicates less than 5 inches Hg of vacuum, replace the fuel injection pump. Refer to «Fuel Injection Pump Replacement»(ref-184139-S15894787592005082200000) . Then go to step 28.
  28. Remove the transparent hose if necessary and attach any disconnected components or fuel lines.
  29. Prime the fuel system 30 times to remove the air in the fuel hoses
  30. Clean any fuel spillage.
  31. Start the engine. If the engine starts and stalls, repeat step 29.
  32. Run the engine to check for fuel leakage.
  33. Verify that the customer concern is corrected. If the customer concern is not corrected, go to «Symptoms - Engine Controls»(ref-184194-S02322581032005082200000) .

The fuel flows through a pre-filter screen in the tank and to the engine through the fuel supply lines. There is no lift pump in the fuel tanks or on the frame. The fuel passes through the base plate of the fuel injector control module (FICM) to cool the module. From the FICM the fuel flows to the fuel filter assembly, which combines a water separator, a prime pump and a filter element. Within the assembly, there is also a fuel heater that operates at fuel temperatures of 6° C (42° F) and below. An integrated hand pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn to the supply pump from the primary fuel tank by the supply pump and delivered to the high-pressure pump.

The much larger section of the pump assembly is the high-pressure fuel injection pump. The pump is engine-driven by the camshaft gear. From the high-pressure pump, the fuel flows through the junction block. The junction block routes pressurized fuel to both common fuel rails. Each common fuel rail supplies one bank of four fuel injectors.

The Fuel Return System routes fuel from the fuel injectors, the junction block, and the fuel injection pump. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.

From the Engine to the Tank

  1. Disconnect the return line at the engine, metal collar.
  2. Remove the fuel filler cap.
  3. Apply 1 psi air at the fuel return line that leads back to the tank.
  4. Listen at filler tube for air.
  5. If air is present, return line is okay. If air is not present, disconnect the return line at the sender assembly.
  6. Retest using 1 psi at the fuel return line back to the tank. If air is present, the return line is okay. Check and replace the sender assembly. If air is not present, repair the restriction in the return line.

From the Engine to the Injector Spill Lines

  1. Disconnect the fuel return line (1) at the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  2. Remove the air duct from the air cleaner assembly to the turbo inlet.
  3. Remove the air intake pipe. Refer to «Air Intake Pipe Replacement»(ref-184139-S39919690542005082200000) .
  4. Remove the fuel return rubber hose of the fuel injection pump from the junction block (2). Cap the fitting on the block with a 3/8 inch rubber cap (1) to prevent fuel leakage.
  5. Install the J 23738-A Vacuum Pump at the fuel return pipe.
  6. Apply 15 inches Hg of vacuum to the pipe. If the vacuum holds, go to step 13. If the vacuum does not hold, go to step 7.
  7. Remove the generator. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  8. Remove the fuel return line (1) connecting the right front and left rear cylinder heads.
  9. Install the J 23738-A onto the right front cylinder head return port (1).
  10. Apply 15 inches Hg of vacuum to the port. If the vacuum holds, go to step 11. If the vacuum does not hold, the leak is in the spill lines under the valve cover. Install the fuel return line between the cylinder heads, remove the lower right valve cover, and go to step 15 of Fuel Leaks (inside of Engine). Refer to «Valve Rocker Arm Cover Replacement - Lower Right»(ref-184191-S15957937092005082200000) in Engine Mechanical and «Fuel Leaks (Outside of Engine)»(ref-184194-S03933432152005082200000) or «Fuel Leaks (Inside of Engine)»(ref-184194-S09618419462005082200000) .
  11. Install the J 23738-A onto the left rear cylinder head return port.
  12. Remove the cap (1) from the junction block (2).
  13. Apply 15 inches Hg of vacuum to the port. If the vacuum holds, replace the leaking fuel return line between the cylinder heads. If the vacuum does not hold, the leak is in the spill lines under the valve cover. Install the fuel return line between the cylinder heads, remove the lower right valve cover, and go to step 15 of Fuel Leaks (inside of Engine). Refer to «Valve Rocker Arm Cover Replacement - Lower Left»(ref-184191-S40011019652005082200000) in Engine Mechanical and «Fuel Leaks (Outside of Engine)»(ref-184194-S03933432152005082200000) or «Fuel Leaks (Inside of Engine)»(ref-184194-S09618419462005082200000) .
  14. Reinstall the fuel injection pump fuel return hose on the junction block and clamp the hose.
  15. Install the air duct on the air cleaner assembly to the turbo inlet.
  16. Install the air intake pipe. Refer to «Air Intake Pipe Replacement»(ref-184139-S39919690542005082200000) .
  17. Reinstall the fuel return line to the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  18. Install the generator. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  19. Start and idle the engine, and check for leaks.

Fuel Leaks (Outside of Engine)

  1. Remove the upper intake manifold sight shield using the following procedure: Remove the retaining bolt in the front of the shield. Lift up on the front of the shield. Lift the shield off the rear bracket.
  2. Clean all of the fuel lines between the fuel injection pump and the fuel injectors using brake cleaning solvent, and let dry.
  3. Add 8 ounces of oil dye to the fuel tank. On dual tanks add the dye to the front, or primary, tank. Refer to «Fuel System Description»(ref-184139-S19045445592005082200000) .
  4. Connect a scan tool to the DLC.
  5. Start and idle the engine for 3-5 minutes.
  6. Command the fuel pressure control to 160 MPa (23,206 psi) with a scan tool.
  7. Inspect for fuel leaks around the fuel injection pump, junction block, fuel rails, and fuel injector supply lines with a J 28428-E High Intensity Black Light Kit. Tighten or replace any leaking lines or components. Refer to the following: «Fuel Injection Line Routing Diagram»(ref-184139-S14508326482005082200000) «Fastener Tightening Specifications»(ref-184139-S25281075032005082200000) «Fuel Rail Assembly Replacement - Bank 1»(ref-184139-S18044277232005082200000) «Fuel Rail Assembly Replacement - Bank 2»(ref-184139-S21405168062005082200000) «Fuel Junction Block Replacement»(ref-184139-S15378516912005082200000) «Fuel Injection Pump Replacement»(ref-184139-S15894787592005082200000)

Fuel Leaks (Inside of Engine)

IMPORTANTIf you were directed here from Fuel Return System Diagnosis, go directly to step 16. This will be performed with the same components disconnected as stated in that test. If you were directed here from the Engine Cranks but Does Not Run diagnostic, go directly to step 2.
  1. Test the high pressure fuel system performance. Start and idle the engine. Command the fuel pressure to 160 MPa with a scan tool. Observe the Actual Fuel Rail Pressure parameter with a scan tool If the Actual Fuel Rail Pressure parameter is within 2 MPa of commanded pressure, continue this diagnostic. If the Actual Fuel Rail Pressure parameter is not within 2 MPa of commanded pressure, go to «Fuel System Diagnosis - High Pressure Side»(ref-184194-S42822038162005082200000) .
  2. Disconnect the fuel return line (1) at the engine. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-184139-S13007011312005082200000) .
  3. Remove the air duct from the air cleaner assembly to the turbo inlet.
  4. Remove the air intake pipe. Refer to «Air Intake Pipe Replacement»(ref-184139-S39919690542005082200000) .
  5. Remove the fuel return rubber hose of the fuel injection pump from the junction block (2). Cap the fitting on the block with a 3/8 inch rubber cap (1) to prevent fuel leakage.
  6. Install the J 23738-A Vacuum Pump at the fuel return pipe.
  7. Apply 15 inches Hg of vacuum to the pipe. If the vacuum holds, reinstall the disconnected components and go to step 23. If the vacuum does not hold, go to step 8.
  8. Remove the generator. Refer to «Generator Replacement (4.3L Engine)»(ref-184144-S33974241872005082200000) or «Generator Replacement (4.8L, 5.3L, and 6.0L Engines)»(ref-184144-S04235530972005082200000) or «Generator Replacement (6.6L (LB7) Engine)»(ref-184144-S05774264832005082200000) or «Generator Replacement (6.6L (LLY) Engine)»(ref-184144-S21907438982005082200000) or «Generator Replacement (8.1L Engine)»(ref-184144-S35508253322005082200000) in Engine Electrical.
  9. Disconnect the fuel return line (1) from the right front cylinder head.
  10. Install a black hose (1) from the J 45873 Fuel Return Volume Test Kit on to the each cylinder head return port.
  11. Install the J 23738-A onto each black hose and apply 15 inches Hg of vacuum to each port and record if each side holds vacuum.
  12. Perform the lower valve cover removal procedure for the bank(s) that did not hold vacuum. Refer to «Valve Rocker Arm Cover Replacement - Lower Right»(ref-184191-S15957937092005082200000) and «Valve Rocker Arm Cover Replacement - Lower Left»(ref-184191-S40011019652005082200000) in Engine Mechanical - 6.6L. Then go to step 13.
  13. Connect the fuel return lines on both cylinder heads. Tighten: Tighten the bolts to 15 N.m (11 lb ft).
  14. Install the J 42964-1 3/8 Fuel Pipe Shut-Off Valve (2) to the fuel return line (1).
  15. Install the J 35800-A Fuel Injector Cleaner on the J 42964-1 port closest to the fuel return line.
  16. Ensure that the shutoff valve is closed.
  17. Add 10 ounces of diesel fuel and 4 ounces of oil dye to the J 35800-A .
  18. Connect the shop air supply to the J 35800-A .
  19. Adjust the pressure regulator on the J 35800-A to 15 psi.
  20. Clean the fuel injectors and fuel return lines with brake cleaning solvent and let dry.
  21. Open the valve on the bottom of the J 35800-A canister.
  22. Inspect for leaks around the fuel injectors and the spill lines with a J 28428-E High Intensity Black Light Kit. Then go to step 30.
  23. Remove both upper valve covers. Refer to «Valve Rocker Arm Cover Replacement - Upper Left»(ref-184191-S25910732682005082200000) and «Valve Rocker Arm Cover Replacement - Upper Right»(ref-184191-S09220022382005082200000) in Engine Mechanical - 6.6L.
  24. Remove the engine oil fill tube on the front engine cover. Refer to «Oil Fill Tube Replacement»(ref-184191-S11543010562005082200000) in Engine Mechanical - 6.6L.
  25. Install the fuel injector feed pipes. Tighten: Tighten the fuel feed pipes to 44 N.m (32 lb ft).
  26. Add 8 ounces of oil dye to the fuel tank. On dual tank systems add the dye to the front, or primary, tank. Refer to «Fuel System Description»(ref-184139-S19045445592005082200000) .
  27. Start the engine.
  28. Increase the fuel pressure to 160 MPa with a scan tool.
  29. Inspect for leaks around the fuel injectors and the fuel injection pump drive gear with a J 28428-E . Then go to step 30.
  30. Tighten or replace any leaking components or gaskets.
  31. Perform the lower valve cover installation procedures as necessary. Refer to «Valve Rocker Arm Cover Replacement - Lower Left»(ref-184191-S40011019652005082200000) and «Valve Rocker Arm Cover Replacement - Lower Right»(ref-184191-S15957937092005082200000) in Engine Mechanical - 6.6L.
  32. Retest the system for engine oil dilution by performing the following procedure: Drain the engine oil from the crankcase and refill. Run the engine at idle for 10 minutes. Stop the engine and wait 10 minutes, then check the oil level on the Dip Stick. This will be the initial oil level. Run the engine at idle for 5 minutes while commanding the fuel pressure to 160 MPa with a scan tool. Stop the engine and wait 10 minutes, then check the oil level on the Dip Stick. If the engine oil level is not more than 3/16 inch above the initial oil level, the system is OK. If the engine oil level is more than 3/16 inch above the initial oil level, go to step 31.F. Run the engine at idle again for 5 minutes while commanding the fuel pressure to 160 MPa with a scan tool. Stop the engine and wait 10 minutes, then check the oil level on the Dip Stick. If the engine oil level is not more than 3/16 inch above the last oil level, the system is OK. If the engine oil level is more than 3/16 inch above the last oil level, go back to step 1.

The fuel flows through a pre-filter screen in the tank and to the engine through the fuel supply lines. There is no lift pump in the fuel tanks or on the frame. The fuel passes through the base plate of the fuel injector control module (FICM) to cool the module. From the FICM the fuel flows to the fuel filter assembly, which combines a water separator, a prime pump and a filter element. Within the assembly, there is also a fuel heater. An integrated hand pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn to the supply pump from the primary fuel tank by the supply pump and delivered to the high-pressure pump.

The much larger section of the pump assembly is the high-pressure fuel injection pump. The pump is engine-driven by the camshaft gear. From the high-pressure pump, the fuel flows through the junction block. The junction block routes pressurized fuel to both common fuel rails. Each common fuel rail supplies one bank of four fuel injectors.

The Fuel Return System routes fuel from the fuel injectors, the junction block, and the fuel injection pump. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.

IMPORTANTIf you were not referred to this test from another diagnostic, do not perform this procedure. Only perform this test when the fuel is more than 18° C (65° F). The fuel return volumes vary based on the API rating of the diesel fuel. A fuel injector may have high fuel return flow only at higher engine temperatures.
  1. Were you referred here from one of the following diagnostics? DTC P1094 Surges/Chuggles in Symptoms Rough, Unstable, or Incorrect Idle in Symptoms Fuel Injector Balance Test with Tech 2 If you answered Yes, go to the Fuel Pressure Regulator Graphing after step 48. If you answered No, go to Step 2.
  2. Remove the air duct from the air cleaner assembly and the turbo inlet.
  3. Remove the air intake pipe. Refer to «Air Intake Pipe Replacement»(ref-184139-S39919690542005082200000) .
  4. Drain the coolant and remove the water outlet tube. Refer to «Water Outlet Tube Replacement (6.6L (LB7) Engine)»(ref-184167-S14199026622005082200000) or «Water Outlet Tube Replacement (6.6L (LLY) Engine)»(ref-184167-S28051507212005082200000) in Engine Cooling.
  5. Remove the fuel injection pump fuel return rubber hose from the junction block (2). Cap the fitting on the block with a 3/8 inch rubber cap (1) to prevent fuel leakage.
  6. Attach a rubber hose (1) with a barbed fitting to the fuel injection pump return hose and insert the other end into a 1 gallon clean fuel container (2).
  7. Remove the ignition 1 relay or EDU relay, as equipped, using the J 43244 Relay Puller Pliers.
  8. Remove the glow plug harness bracket bolt.
  9. Remove the glow plug harness bracket nut from the valve cover.
  10. Remove the glow plug controller/relay mounting nuts.
  11. Reposition the glow plug controller/relay.
  12. Remove the fuel line retainers.
  13. Remove the banjo bolt (2) from left rear cylinder head.
  14. Install the black hose (1) of the J 45873 Fuel Return Volume Test Kit to the left rear cylinder head and install the other end of the hose into one of the J 45873 graduated cylinders.
  15. Remove the banjo bolt (3) from the leak-off block.
  16. Install the other black hose (1) of the J 45873 to the leak-off block (2) and install the other end of the hose into another J 45873 graduated cylinders.
  17. Remove the banjo bolt (4) from the junction block (2).
  18. Crank the engine for 15 seconds while observing the fuel pressure relief valve on the junction block for fuel leakage. If fuel is leaking from the fuel pressure relief valve, replace the fuel pressure relief valve. Refer to «Fuel Pressure Relief Valve Replacement»(ref-184139-S08854486682005082200000) . If no fuel is leaking from the fuel pressure relief valve, go to step 19.
  19. Crank the engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or both of the J 45873 graduated cylinders (1).
  20. Elevate the hoses (2) to retain the fuel in the hoses, and empty the graduated cylinders into a suitable container.
  21. Install the hoses (2) into 2 of the graduated cylinders (1).
  22. Crank the engine for 15 seconds.
  23. Measure the quantity of fuel in each of the graduated cylinders. Refer to «Fuel System Specifications»(ref-184139-S35871131322005082200000) for fuel return flow specifications. If there is more than the specified quantity of fuel from either cylinder bank, remove the valve cover from that bank. Refer to «Valve Rocker Arm Cover Replacement - Lower Left»(ref-184191-S40011019652005082200000) or «Valve Rocker Arm Cover Replacement - Lower Right»(ref-184191-S15957937092005082200000) , then go to step 24. If there is less than the specified quantity from each cylinder bank, replace the fuel injection pump and repeat steps 19-23. If the fuel injection pump has already been replaced in this repair and there is less than the specified quantity of fuel from each bank, go to step 45.
  24. Remove the return line from injectors.
  25. Install the four yellow hoses (2) from the J 45873 to the injectors (1) and the other end of the hoses into each of the J 45873 graduated cylinders.
  26. Install the 4 injector supply lines. Tighten: Tighten the supply lines to 44 N.m (32 lb ft).
  27. Connect the engine-to-chassis harness connectors to enable the starter.
  28. Install the fuel filter hoses, FICM hoses, and the fuel supply hose. Push the fuel supply hose in until it locks.
  29. Install the black hoses from the J 45873 into the container that the fuel injection pump return hose is in. Prime the fuel system 30 times to remove air from the fuel system. Air will be forced out of the system within 2 minutes.
  30. Crank the engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or more of the graduated cylinders.
  31. Elevate the 4 hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
  32. Install the hoses in the graduated cylinders in numerical order.
  33. Crank the engine for 15 seconds.
  34. Measure the quantity of fuel in each of the graduated cylinders. Refer to «Fuel System Specifications»(ref-184139-S35871131322005082200000) for fuel return flow specifications. Remove the fuel feed pipes from any injectors that have high return fuel flow, and install the EN 47589 Fuel Pressure Test Adapter Cap(s) to the fuel rail outlets. Then go to step 35.
  35. Repeat steps 30 through 34 until no fuel injectors have more than the specified quantity of fuel flow.
  36. Were both banks of fuel injectors tested with steps 30 through 35? If the answer is YES, go to step 44. If the answer is NO, go to step 37.
  37. Ensure that the hoses are still installed as they were in steps 14 through 17.
  38. Prime the fuel system 30 times to remove the air from the fuel system. Air will be forced out of the system within 2 minutes.
  39. Crank the engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or both of the J 45873 graduated cylinders (1).
  40. Elevate the hoses (2) to retain the fuel in the hoses, and empty the graduated cylinders into a suitable container.
  41. Install the hoses (2) into 2 of the graduated cylinders (1).
  42. Crank the engine for 15 seconds.
  43. Measure the quantity of fuel in each of the graduated cylinders. Refer to «Fuel System Specifications»(ref-184139-S35871131322005082200000) for fuel return flow specifications. If there is more than the specified quantity of fuel in either of the 2 cylinders, remove the valve cover from that cylinder head. Refer to «Valve Rocker Arm Cover Replacement - Lower Left»(ref-184191-S40011019652005082200000) or «Valve Rocker Arm Cover Replacement - Lower Right»(ref-184191-S15957937092005082200000) . Then perform steps 29 through 35 on the bank of fuel injectors with the high fuel flow, Then go to step 44. If both of the cylinder have less than the specified quantity of fuel, go to step 44.
  44. Replace all of the fuel injectors that had fuel rail outlets capped. Refer to «Fuel Injector Replacement»(ref-184139-S17626859932005082200000) .
  45. Install all disconnected and removed components. Refer to the applicable procedures.
  46. Start and idle the engine. You may have to prime the fuel system before the engine will start.
  47. Connect a scan tool.
  48. Command the fuel pressure control to 160 MPa with a scan tool. If the fuel pressure is more than 145 MPa, the system is OK. If the fuel pressure is unable to increase to more than 145 MPa, replace the fuel injection pump. Refer to «Fuel Injection Pump Replacement»(ref-184139-S15894787592005082200000) .

Scheme 455

Scheme 455: Fuel Pressure Regulator Graphing
Scheme 455: Fuel Pressure Regulator Graphing

Scheme 456

Scheme 456
Scheme 456

Scheme 457

Scheme 457
Scheme 457
  1. Set up the scan tool in the following format: Select the Data Display on the scan tool. Select Engine Data 1. Select the More softkey 2 times. Select the Live Plot softkey. Select the Engine Speed, Actual Fuel Rail Pressure, and Desired Fuel Rail Pressure parameters by highlighting each parameter and depressing the ENTER softkey. Select the Accept softkey. Select the More softkey, then select the Change Min/Max softkey. Select the More softkey, and adjust the parameters to the following Min/Max ranges: The Engine Speed Min/Max range is 0 to 1000 RPM. The Actual Fuel Rail Pressure Min/Max range is 1.0 to 160 MPa. The Desired Fuel Rail Pressure Min/Max range is 1.0 to 160 MPa.
  2. Start and idle the engine.
  3. Observe the live plot for sharp changes in the Actual Fuel Rail Pressure above and below the Desired fuel rail pressure while performing one of the following actions: Idling the engine. Shifting the transmission from Park to Drive, and back to Park. Turning the steering wheel from lock to lock. Turning the air conditioning ON and OFF. Callout Component Name 1 Engine Speed 2 Actual Fuel Rail Pressure 3 Desired Fuel Rail Pressure Callout Component Name 1 Engine Speed 2 Actual Fuel Rail Pressure 3 Desired Fuel Rail Pressure Callout Component Name 1 Engine Speed 2 Actual Fuel Rail Pressure 3 Desired Fuel Rail Pressure
  4. If there is a violent fluctuation in the Actual Fuel Rail pressure, as seen in the third Graphic above, replace the fuel pressure regulator. Refer to «Fuel Pressure Regulator Replacement»(ref-184139-S38224987542005082200000) .

Leak Check Procedure

CAUTIONPlace a dry chemical (Class B) fire extinguisher near the area before performing a Fuel Tank Leak Check. Before removing the fuel tank for a suspected leak, make sure that the fuel pipes or the tubes are not leaking onto the tank. Once removed, make sure that the fuel is not leaking around the fuel sender O-ring. Failure to follow these precautions may result in personal injury.

This check requires the fuel sender and the O-ring to be installed.

  1. Disconnect the battery cables.
  2. Drain the fuel tank. Refer to «Fuel Tank Draining Procedure»(ref-184139-S16015704432005082200000) .
  3. Remove the fuel tank. Refer to «Fuel Tank Replacement (Pickup)»(ref-184139-S25222812662005082200000) or «Fuel Tank Replacement (Cab/Chassis - Front)»(ref-184139-S15896634012005082200000) or «Fuel Tank Replacement (Cab/Chassis - Rear)»(ref-184139-S14458213192005082200000) .
  4. Cap the fuel feed tube and the fuel return tube on the fuel sender.
  5. Connect a piece of hose to the filler tube nipple and plug the opposite end.
  6. Submerge the tank in water or apply a soap solution to the outside of the tank.
  7. Apply 35 kPa (5 psi) of air pressure to the vent hose of the fuel tank. A leak will show up as bubbles.

Conditions for Updating the I/M System Status

Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the malfunction indicator lamp (MIL). Once all of the tests are completed, the I/M System Status display will indicate YES in the Completed column. For example, when the Component Monitoring Test indicates YES, all of the comprehensive components have been diagnosed. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

  1. The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
  2. The battery has been disconnected or discharged below operating voltage.
  3. The control module power or ground has been interrupted.
  4. The control module has been reprogrammed.
  5. The control module DTCs have been cleared as part of a service procedure.

Monitored Emission Control Systems

The OBD II System monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following

  1. Comprehensive component monitoring - Emission related inputs and outputs
  2. Exhaust gas recirculation (EGR) system
  3. Misfire monitoring

For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table .

More articles — Engine Controls - 6.6L (LB7) (Troubleshooting & Diagnosis