DD15 Aerated Fuel Troubleshooting

This condition will exist if there is an external leak of the low pressure fuel system, combustion pressure entering the fuel system, or a vehicle fuel system concern.‪

Check as follows‪

1. Install J-48709 sight glass tools on to fuel filter module.
   

   ENGINE EXHAUST ‪
   To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area. Engine exhaust is toxic.‪

   
2. Start engine and allow it to reach operating temperature (over 140°F/60°C).
3. At idle and 1800 rpm watch the fuel inlet and outlet sight glasses at the fuel filter module.
   1. If the fuel is aerated, go to next step.
   2. If the fuel is not aerated, move to other troubleshooting procedures.
4. Install J-48707 and J-48708. This will allow the engine to be isolated from the chassis.
   
5. Start engine and allow it to reach operating temperature (over 140°F/60°C).
6. At idle and 1800 rpm watch the fuel inlet and outlet sight glasses at the fuel filter module.
   1. If the fuel is aerated at idle, go to next step.
   2. If the fuel is aerated at 1800 RPM only; go to step 8 .
   3. If the fuel is not aerated, inspect the fuel system from the fuel filter module back to the fuel tanks.
7. Install J-48710 to the fuel filter module. Refer to “16.4 External and Internal Low Pressure Fuel Leaks” , “External and Internal Low Pressure Fuel Leaks” in the “Diagnostic Tests” chapter.
   1. If leaks were found, repair as necessary.
   2. If no leaks were found, go to next step.
8. Using DDDL, run the Compression Test.
9. Note any cylinders that show lower than normal compression
10. Using DDDL, run the Cylinder Compression Test.
11. Note any cylinders that show lower than normal compression.
12. Compare the cylinders that show lower than average torque loss to the cylinders that show lower than normal compression. Example: If cylinder #1 shows low torque loss and low compression, inspect this cylinder first
13. Remove suspect injector.
    1. If copper washer and injector show signs of blow-by, replace copper washer and replace all fuel filters
    2. Before installing new injector, inspect injector cup for corrosion. Replace if necessary.
14. Retest the system.