Probable Causes
- Air in fuel
- Low fuel quality
- Incorrect fuel timing dimension
- Faulty unit injectors
- Improper unit injector synchronization
- Mechanical problem
Recommended Repairs
Air In Fuel
If air in the fuel is suspected, refer to Troubleshooting, "Air In Fuel".
Low Fuel Quality
Remove the fuel from the fuel tank. Install a new fuel filter element. Put a good grade of clean fuel in the tank. Refer to Troubleshooting, "Fuel Quality".
Incorrect Fuel Timing Dimension
Check the fuel timing dimension and make necessary adjustments. Refer to Systems Operation, Testing And Adjusting.
Faulty Unit Injectors
Use the 1U-6661 Pop Tester Group to check the unit injectors for proper operation. Refer to Special Instruction, SEHS9787. Use the go/no-go gauge to check the unit injector height. Check the injectors for external leakage.
Improper Unit Injector Synchronization
Improper unit injector synchronization will cause more fuel to be delivered to one cylinder. This will cause an engine knock. To determine the cylinder that is receiving excess fuel, move each injector to the fuel-on position and listen for an engine knock. Synchronize the injectors, if necessary. Refer to Systems Operation, Testing And Adjusting.
Mechanical Problem
A mechanical problem could produce noise. Find the problem and correct the problem. Possible problems include the following items:
- Incorrect valve adjustment
- Sticking valve
- Internal mechanical problem