Engine Controls - Basic Diagnostic Procedures - 6.6L Diesel: Other Chevrolet Silverado 1500 HD

Cylinder Compression Pressure

Check engine mechanical condition with compression gauge, vacuum gauge, or engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see ENGINE COMPRESSION SPECIFICATIONS table.

ENGINE COMPRESSION SPECIFICATIONS

Cylinder Combustion Pressure Leakage

1. Disconnect battery negative terminal. Remove glow plugs. Rotate crankshaft to place piston in the cylinder being tested at Top Dead Center (TDC) of compression stroke. Install Cylinder Head Leakdown Adapter (J-35667-9) and Cylinder Head Leakdown Tester (J-35667-A).
2. Apply air pressure to cylinder leakdown tester. Record cylinder leakage readings for each cylinder. Any cylinder with 25 percent leakage or more requires service.
3. Inspect following primary areas in order to properly diagnose a leaking cylinder. Air leakage sounds at the intake manifold tube may indicate a worn, stuck or burnt intake valve, broken valve spring, incorrect valve lash or damaged valve train components. Air leakage sounds at the exhaust system tailpipe may indicate a worn, burnt, or stuck exhaust valve, broken valve spring, incorrect valve lash or damaged valve train components. Air leakage sounds from the crankcase, oil level indicator tube, or oil fill tube may indicate worn piston rings, a damaged piston, a worn or scored cylinder bore, a damaged engine block or a damaged cylinder head. Air bubbles in the cooling system may indicate a damaged cylinder head, gasket, or leaking injector tube.
4. After performing test, remove leakdown tester. Install spark plugs and reconnect negative battery terminal.

Preliminary Checks

Before performing following tests, check battery condition, engine cranking speed and for adequate fuel in tank. Perform diagnostic system check following any repairs. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article.

FUEL SYSTEM PRIMING

Note. In order for the DURAMAX™ diesel engine fuel system to work properly, the fuel lines must be full of fuel and contain no air. If air gets into the fuel lines, it will be necessary to prime the fuel system to eliminate the air before operating the vehicle. Air could have entered to system in one of the following ways: Vehicle ran out of fuel. Filter was removed for service or replacement. Fuel lines were removed or disconnected for servicing. Fuel filter water drain cock was opened while the engine was running. If one or more of these conditions occurred, air has entered the fuel system and you will need to prime the system prior to operating the vehicle.

Priming Procedures

1. Prior to priming the engine, ensure that there is fuel in fuel tank, fuel filter has been installed and properly tightened, fuel lines are properly connected, fuel filter is cool to the touch, and any dirt or debris is removed from fuel filter head and vent valve.
2. Open vent valve, located on top of fuel filter housing, by turning the screw counterclockwise several full turns. (Схема №5)
3. Operate the priming pump until a small amount of fuel seeps from the vent valve. Allow pump to return upwards between pumps. When fuel is present, the filter is full of fuel and system should be primed.
4. Close the vent valve.
5. Clean any fuel which accumulated on the fuel filter.
6. Start the engine and allow it to idle for a few minutes.
7. Check filter for leaks.

Fuel System Air Leak Check

1. Install a Vacuum Gauge (J-44638) to the fuel system service port, located on 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 fuel supply lines.
4. Prime the fuel manager until 10 psi is indicated on the vacuum gauge.
5. Check for external fuel leaks between the fuel filter/heater assembly and the fuel injection pump. (Схема №4) If fuel is leaking externally, replace or repair the leaking component. If no external fuel leaks are found, go to next step.
6. Reprime the fuel system until 10 psi is indicated on the vacuum gauge. If fuel pressure drops from 10 psi to 2 psi in less than one minute, go to step 23. If fuel pressure drops from 10 psi to 2 psi in more than one minute, go to next step.
7. Disconnect fuel supply line at engine.
8. Cap off the fuel supply pipe on the engine with a 1/2" rubber plug and clamp the plug.
9. Disconnect fuel return line at the engine.
10. Install a hand-held vacuum pump on the fuel return pipe on the engine.
11. Check the fuel system components on top of the engine for vacuum leaks. Apply at least 25 in. Hg to the fuel return pipe and wait more than one minute for the system to stabilize. Repeat 6 six times. Observe vacuum gauge. If vacuum does not drop below 8 in. Hg within 10 minutes, go to next step. If vacuum drops below 8 in. Hg within 10 minutes, go to step 16.
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 fuel filter inlet, with a vertical loop to observe the incoming fuel for air bubbles. FICM is located on top front right of engine.
14. Install generator.
15. Prime the fuel system 30 times to remove the air from the fuel hoses. If engine does not start in the next step, go to step 23. Engine must be run for at least 10 minutes to allow the fuel system to stabilize and remove all air from the fuel system.
16. Start 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 okay. Go to step 28. If any air bubbles are entering the transparent hose with the incoming fuel, turn engine off 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 from outlet pipe of the fuel filter assembly. (Схема №4) Open the drain on the fuel filter assembly and drain the fuel into a suitable container. Close the drain. Install vacuum gauge on the outlet port of the fuel filter assembly. Apply 15 in. Hg to the fuel pipe and observe the vacuum gauge. If vacuum does not drop, connect the fuel supply line at the engine and go to next step. If vacuum drops, repair air leak between fuel supply line fitting and fuel filter assembly. Remove vacuum gauge from outlet port of the fuel filter assembly and install vacuum gauge to fuel outlet hose. Remove the air intake pipe. Remove supply hose from fuel injection pump and plug hose. Apply 15 in. Hg and observe reading. If vacuum drops, repair leak between fuel filter assembly outlet and fuel injection pump inlet. If vacuum does not drop, go to next step. Disconnect fuel injection pump return hose. Cap off fuel return pipe on fuel injection pump with a 5/16" rubber plug and clamp the plug. Install vacuum gauge to fuel inlet pipe of the fuel injection pump. Apply 20 in. Hg and observe vacuum hose. If vacuum drops, replace fuel injection pump, then go to step 28. If vacuum does not drop, replace fuel injection pump inlet supply hose, then go to step 28.
19. Check the fuel sender for air leakage. Remove front fuel tank. Remove fuel sender from the fuel tank. Remove strainer from fuel sender and plug the bottom end of the pickup tube. Apply 15 in. Hg to the upper end of the pickup tube and observe vacuum gauge. If 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 sealing surfaces are not damaged, replace fuel line between the chassis line and the fuel sending unit, then go to step 20. If vacuum does not hold, replace fuel sender. Reinstall 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 operate engine.
22. Observe 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 okay. 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 vacuum gauge is installed.
26. Remove ignition 1 relay. Relay is located in underhood fuse/relay block.
27. Crank engine 2-3 times in 15 second intervals and observe vacuum gauge. If vacuum gauge indicates 5 in. Hg or more, go to next step. If vacuum gauge indicates less than 5 in. Hg, replace fuel injection pump, then go to next step.
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 engine. If engine starts and stalls, repeat step 29.
32. Operate engine to check for fuel leakage.
33. Verify that the customer's concern is corrected. If customer concern is not corrected, go to «SYMPTOMS»(ref-152999-S03767149722003031000000) in TROUBLE SHOOTING - NO CODES - 6.6L SIERRA & SILVERADO - DIESEL article.

1. Install Vacuum Gauge (J-44638) to fuel system service port on right front side of engine.
2. Remove air duct from air cleaner assembly to turbo inlet.
3. Remove generator for visibility of fuel supply lines.
4. Prime fuel manager until 10 psi is indicated on vacuum gauge.
5. Check for external fuel leaks between fuel filter/heater assembly and fuel injection pump. (Схема №4) If fuel is leaking externally, replace or repair the leaking component. If no external fuel leaks are found, go to next step.
6. Reprime fuel system until 10 psi is indicated on the vacuum gauge. If fuel pressure drops from 10 psi to 2 psi in less than one minute, go to step 24. If fuel pressure drops from 10 psi to 2 psi in more than one minute, go to next step.
7. Disconnect fuel supply line at engine.
8. Cap off the fuel supply pipe on the engine with a 1/2" rubber plug and hose clamp.
9. Disconnect fuel return line at engine.
10. Install a hand-held vacuum pump on fuel return pipe on engine.
11. Check fuel system components on top of the engine for vacuum leaks. Apply at least 25 in. Hg to fuel return pipe with the hand-held vacuum pump and wait more than one minute for the system to stabilize. Repeat this step 6 times. Observe vacuum gauge. If vacuum does not drop below 8 in. Hg within 10 minutes, go to next step. If vacuum drops below 8 in. Hg within 10 minutes, go to step 22.
12. Reconnect fuel supply line and return line at engine. (Схема №4)
13. Disconnect the chassis fuel line from the short fuel line between the fuel sender and chassis fuel line in front of the fuel tank.
14. Plug the chassis fuel line using a 1/2" rubber plug and clamp the plug.
15. Check the fuel system components on top of the engine for vacuum leaks. Apply at least 25 in. Hg to fuel return pipe and wait more than one minute for the system to stabilize. Repeat 10 times. Observe vacuum gauge. If vacuum does not drop below 8 in. Hg within 10 minutes, go to next step. If vacuum drops below 8 in. Hg within 10 minutes, inspect the "O" ring sealing surfaces of the engine fuel supply line for damage and correct as necessary. If sealing surfaces are not damaged, replace chassis fuel lines and go to step 29.
16. Reconnect fuel line at fuel tank and fuel return line at 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. FICM is located on top right front of engine.
18. Install generator.
19. Prime fuel system 30 times to remove the air in the fuel system.
20. Start and operate engine at idle.
21. Observe 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 okay. Go to step 29. If any air bubbles are entering the transparent hose with the incoming fuel, turn engine off and go to step 23.
22. Check fuel injection pump and on-engine fuel suction system for air leakage. Disconnect the fuel outlet hose from the outlet pipe of the fuel filter assembly. Open drain on the fuel filter assembly and drain fuel into a suitable container. Close the drain. Install hand-held vacuum pump on outlet port of the fuel filter assembly. Apply 15 in. Hg of vacuum to the fuel pipe and observe vacuum gauge. If vacuum does not drop, connect the fuel supply line at the engine and go to next step. If vacuum drops, repair air leak between the fuel supply line fitting and fuel filter assembly. Install hand-held vacuum pump to fuel outlet hose from the fuel filter assembly. Remove air intake pipe. Remove supply hose from the fuel injection pump and plug the hose. Apply 15 in. Hg of vacuum and observe the reading. If the vacuum drops, repair the leak between the fuel filter assembly outlet and fuel injection pump inlet. If vacuum does not drop, go to next step. Disconnect fuel injection pump return hose. Cap off the fuel return pipe on the fuel injection pump with a 1/2" rubber plug and clamp the plug. Install hand-held vacuum pump to fuel inlet pipe of the fuel injection pump. Apply 20 in. Hg and observe vacuum gauge. If vacuum drops, replace fuel injection pump, then go to step 29. If vacuum does not drop, replace fuel injection pump inlet supply hose, then go to step 29.
23. Check fuel sender for air leakage. Remove fuel tank. Remove fuel sender from fuel tank. Remove strainer from fuel sender and plug bottom end of the pickup tube. Apply 15 in. Hg to the upper end of the pickup tube and observe vacuum gauge. If vacuum holds, inspect the "O" ring sealing surfaces of fuel sending unit and chassis fuel line for damage and correct as necessary. If sealing surfaces are not damaged, replace fuel line between the chassis line and fuel sending unit, then go to step 29. If vacuum does not hold replace fuel sender, reinstall fuel tank, then go to step 29.
24. Prime fuel system 30 times or until fuel pressure is 10 psi to remove air from fuel system. Air will be forced out of the system within 2 minutes.
25. Remove hose from fuel filter assembly outlet fitting and plug hose.
26. Verify that vacuum gauge is installed.
27. Remove ignition 1 relay. Relay is located in underhood fuse/relay block.
28. Crank engine 2-3 times in 15 second intervals and observe vacuum gauge. If vacuum gauge indicates 5 in. Hg or more, go to step 6. If vacuum gauge indicates less than 5 in. Hg, replace fuel injection pump. After repairs, go to next step.
29. Remove the transparent hose, if necessary and attach any disconnected components or fuel lines.
30. Prime fuel system 30 times to remove air in the fuel hoses
31. Clean any fuel spillage.
32. Start engine. If engine starts and stalls, repeat step 30.
33. Operate engine to check for fuel leakage.
34. Verify that the customer's concern is corrected. If customer's concern is not corrected, go to «SYMPTOMS»(ref-152999-S03767149722003031000000) in TROUBLE SHOOTING - NO CODES - 6.6L SIERRA & SILVERADO - DIESEL article.

IDLE SPEED

Idle speed is controlled by ECM. Incorrect idle speeds are normally caused by dirty throttle plates or vacuum leaks.

SIERRA 2500HD

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SIERRA 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO 2500HD

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.