Description
The ignition relay is normally an open relay. The relay armature is held in the open position by spring tension. When the ignition switch is turned to the RUN or START position, current will flow through the relay coil. A wire connected to the other end of the relay coil completes the path to ground through the ECM. The electromagnetic field created by the relay coil overcomes the spring tension and moves the armature, allowing the contacts to close. The closed relay contacts allow current to flow from the battery to the following fuses
- INJ "B" fuse.
- FUEL HT fuse.
- SBA fuse, if equipped.
When ignition switch is turned to OFF position, the electromagnetic field collapses. This action allows the spring tension to move the armature away from the relay contacts, which interrupts current flow to the fuses.
If ignition relay fails to close, engine will crank but will not run. The Class 2 communications will be available with the use of a scan tool.
Fungi and other microorganisms can survive and multiply in diesel fuel if water is present. The fungi can be present in any part of the fuel handling system. These fungi grow into long strings and will form into large globules. The growths appear slimy and are usually Black, Green or Brown. The fungi may grow anywhere in the fuel, but are most plentiful where diesel fuel and water meet. As fuel is agitated, when service station tanks are being filled, fungi are distributed throughout the tank and may be pumped into a vehicle.
| CAUTION | Avoid physical contact with the biocides in order to avoid personal injury. |
If fungi have caused fuel system contamination, use a diesel fuel biocide to sterilize the fuel system. Do not exceed the dosage recommended. Discontinue use of a biocide when towing a trailer. It is permissible to have biocide in fuel when starting to tow, but do not add any biocide while towing.
Steam cleaning may be necessary if most of the fungus growth cannot be removed with biocides. The presence of water or gasoline in diesel fuel may also cause injection pump and fuel injector damage.
This procedure checks for the presence of water and gasoline in diesel fuel that may cause fuel injection pump and fuel injector damage. Remove and inspect fuel filter. If water, gasoline or fungi/bacteria are not present, end the inspection. If water or fungi/bacteria are present, go to CLEANING WATER FROM FUEL SYSTEM in FUEL SYSTEM CLEANING . If gasoline is present, go to CLEANING GASOLINE FROM FUEL SYSTEM in FUEL SYSTEM CLEANING .
The fuel manager/filter assembly consists of the fuel heater, the water-in-fuel sensor, and a filter. The filter contains the coalescer, the device that combines small droplets of water into larger ones, and the filter/separator. As fuel enters filter, fuel passes through the fuel heater. The heater contains a thermostatic switch that opens or closes to turn the heater OFF or ON, depending on the temperature of the fuel.
The fuel then passes through the filter and water coalescer, where droplets of water in fuel combine into larger drops that fall into the water reservoir in the filter. When fuel flows from the fuel manager/filter assembly to the injection pump, the fuel is clean and free of water. The fuel heater is operated by a built-in thermostatic switch. The thermostatic switch completes the circuit for the fuel heater element when the thermostatic switch senses a temperature below 46°F (8°C).
Test Description
The number below refers to the step number on the diagnostic procedures.
- 7 - This steps checks for a thermostatic switch that completes the circuit.
The fuel manager/filter assembly consists of the fuel heater, the water-in-fuel sensor, and a filter. The filter contains the coalescer, the device that combines small droplets of water into larger ones, and the filter/separator. As fuel enters the filter, the fuel passes first though the fuel heater. The heater contains a thermostatic switch that opens or closes to turn the heater OFF or ON, depending on the temperature of the fuel.
The fuel then passes through the filter and the water coalescer, where the droplets of water in the fuel combine into larger drops that fall into the water reservoir in the filter. When fuel flows from the fuel manager/filter assembly to the injection pump, the fuel is clean and free of water. The fuel heater is operated by a built-in thermostatic switch. The thermostatic switch completes the circuit for the fuel heater element when the thermostatic switch senses a temperature below 46°F (8°C).
The number below refers to the step number on the diagnostic procedures.
- 2 - This step checks for a fuel heater that is stuck ON.
- 3 - This steps checks for a thermostatic switch that completes the circuit.
The Fuel Injector Balance Test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical Diagnostic Trouble Codes (DTCs). During the test the ECM turns off individual injectors while engine is running and scan tool displays engine RPM. If a fuel injector is turned off and there is a different engine speed change observed on the scan tool when compared to the other cylinders, that cylinder has a fuel injector or engine compression condition. If there is a balance rate of more than 4 mm 3 or less than -4 mm 3 on any of the cylinders, that cylinder has a fuel injector or engine compression condition. If a fuel injector is turned off and engine noise or smoke disappears, that cylinder has a fuel injector or engine compression condition.
The numbers below refer to step numbers in diagnostic procedure.
- 3 - A balance rate between -4 mm 3 and +4 mm 3 will not cause a driveability concern. A balance rate less than -4 mm 3 , between 4 mm 3 and 14 mm 3 will cause a driveability concern without any DTCs. A balance rate of more than 15 mm 3 will set a DTC.
- 5 - This step determines if ECM can control a stable fuel pressure. A high balance rate may be caused by a fuel injector or compression only if ECM can control fuel pressure.
The fuel quality hydrometer provides a general indication of fuel quality and should not be considered scientifically accurate. API gravity for No. 1 diesel should be 39-44 and API gravity for No. 2 diesel should be 30-39.
The diagnosis of fuel odor may be a condition of a leaking fuel tank, filler neck or filler cap. A defective filler cap, a plugged or pinched vent pipe can cause a collapsed fuel tank. Loose mounting straps or foreign material in tank may be the cause of a rattle at the fuel tank.
| CAUTION | Place a dry chemical (Class B) fire extinguisher near the area before performing leak check. Before removing fuel tank for a suspected leak, ensure that fuel pipes or tubes are not leaking onto tank. Once removed, ensure that fuel is not leaking around the fuel sender "O" ring. Failure to follow these precautions may result in personal injury. |
The glow plug system is used to assist in providing the heat required to begin combustion during engine starting at cold ambient temperatures. The glow plugs are heated before and during cranking, as well as during the engine operation. The ECM controls glow plug ON times by monitoring coolant temperatures and glow plug voltage. This system check will check the glow plugs and glow plug feed circuit coming from the relay/controller.
The numbers below refer to the step numbers on the diagnostic procedures.
- 2 - This step will make sure there are no other DTCs stored that will affect the operation of the glow plug system.
- 3 - This step will check each glow plug for an open.
- 4 - This step will check each glow plug feed circuit for an open.