Some 2003-2005 Ford F-Super Duty and Excursion, and 2004-2005 E-Series, F-650 and F-750 vehicles equipped with the 6.0L diesel engine may exhibit a misfire, lack of power, buck/jerk, excessive smoke or crank/no-start. There are several potential causes for these symptoms, including injector concerns.
If normal diagnostics lead to an injector concern, use the following diagnostics to confirm the cause of injector failure and/or to rule out other conditions which may cause the same symptoms as failed injectors.
NOTE: If diagnosing a lack of power condition, be aware that 2005 model year vehicles have a “forced limited power” strategy which limits ICP pressure when the fuel tank level gets very low (well after the low fuel light comes on). When this occurs, DTC P115A will be stored in the PCM.
Internal injector damage can be caused by a lack of fuel system supply pressure. Restricted fuel filters and/or fuel lines, or an inoperative fuel pump can create a low or negative fuel supply pressure. Low or negative pressures may hinder the return stroke of the injector intensifier plunger to its rest position, leading to internal injector damage. To diagnose for low or negative fuel pressure and to confirm if any injectors have been damaged, see the following procedure:
- Perform standard diagnostic procedures including verification of supplied fuel pressure while the symptom is evident.
- Repair the causes for low pressure on the supply side of the fuel system.
- Diagnose for failed injector(s) only after rectifying fuel supply pressure.
Inert combustion gas in an injector can cause a random misfire in one or multiple cylinders. Combustion gas may leak past the injector’s needle and seat, or the copper combustion seal. Once the combustion gas enters the fuel rail in the cylinder head, it then distributes to other injectors, typically on the same bank. To diagnose for combustion gas entering the fuel system:
- Remove outlet fuel lines from the fuel filter housing on top of the engine.
- Install a balloon over each fuel line with a zip tie.
- Disable the fuel pump and FICM relays.
- Crank the engine and watch for compression pulses in the balloon.
- For each line where compression pulses are evident, remove all but one of the glow plugs from the affected cylinder head(s).
- Crank the engine and again watch for compression pulses.
- Remove the glow plug and transfer it to the next cylinder in the head and repeat Step 6.
- For each cylinder where compression pulses are evident, remove the injector(s) and inspect the copper gasket and lower O-ring. Replace if necessary. If gaskets and O-rings are OK, replace the injector(s). Re-test and confirm the repair.
Erratic supply of high pressure oil to the injectors may cause a rough running engine. High pressure oil flow can be disrupted by faulty check valves or a faulty IPR valve. To diagnose, first perform a slow neutral run up in Park/Neutral. If the engine runs routgh between 1200 and 1900 RPM, proceed to Check Valve Diagnosis. If the engine runs rough between 3000 and 4000 RPM, replace the IPR valve.
CHECK VALVE DIAGNOSIS
- To isolate the bank with the faulty check valve, disconnect all of the injector electrical connectors on one bank.
- Perform a power balance test. Engine misfires should be constant on the four disconnected cylinders and the operational cylinders should be contributing evenly.
- Repeat Steps 1 and 2 on the opposite bank.
- If the operating contribution is erratic on one bank, replace the check valve on that bank.