76865 Mercruiser SHIFT CRANK

Probable Causes
Fuel injector O-ring seals
High-pressure fuel pump
Fuel injector tip
Fuel transfer pump sealRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in the order of the listed test steps.
Table 1
Troubleshooting Test Steps Values Results
1. Check the Fuel Injector O-ring Seals
A. Pressurize the engine fuel return line with 700 kPa (100 psi) of air pressure. At each of the valve mechanism covers listen for air leaking.
Injector
Result: A leak was not heard.
Proceed to the next step.
Result: A leak was heard.
Repair: Remove the injector and inspect the injector O-ring seals.
Replace damaged seals and retest.
Result: A leak was heard and the O-rings are OK.
Repair: Replace the injector.
Ensure that the new trim files are installed. Refer to Troubleshooting, "Injector Trim File - Install" for details. Use Caterpillar Electronic Technician (ET) to perform a "Fuel System Verification Test". Refer to Troubleshooting, "Injector Solenoid - Test" for details.
If the problem is not resolved, proceed to the next step.
Illustration 1 g03674081
Location of the magnetic plug in the fuel pump adapter (typical example)
(1) Magnetic plug in the fuel pump adapter
Table 2
Troubleshooting Test Steps Values Results
2. Check the High Pressure Fuel Pump
Perform this test on a cold engine.
The fuel pressure in the high-pressure fuel system must be below 1 MPa (145 psi) before this test procedure is performed. Refer to Systems Operation/Testing and Adjusting, "Fuel Rail Pressure - Release" for procedural details.
A. Remove plug (1) from the bottom of the fuel pump adapter. Expect that a small amount of engine oil will drain from the opening. Check the magnetic plug for debris. Clean the plug prior to reinstallation.
B. Use the manual override for the fuel priming pump to run the pump in order to pressurize the fuel system. Allow the pump to run for at least five minutes while you monitor the drain hole in the fuel pump adapter for leakage.
If a manual switch is not available, use the override in Cat ET to operate the fuel priming pump.
For a pump that is in good repair, fuel may drip intermittently from the adapter drain hole. The leakage must not exceed 6 ml/min (0.2 oz/min).
Pump
Result: The pump is OK.
Proceed to the next step.
Result: A continuous stream of fuel is flowing from the drain hole
Repair: Replace the high-pressure fuel pump.
Also replace the in-line high-pressure fuel filter element in the block assembly that is part of the front fuel injection line.
If the problem is not resolved, proceed to the next step.
3. Check the Fuel Injector Tip
This fuel system utilizes flow limiter valves for each injector. An injector that is badly damaged may cause the flow limiter to trip. If the "Cylinder Cutout Test" indicates that a cylinder is not being fueled, check the condition of the fuel injector. If the fuel injector is in good repair, check the flow limiter valve for the affected cylinder. Refer to Systems Operation/Testing and Adjusting, "Fuel Rail Leakage - Check" for information that is related to testing the high-pressure fuel system.
A. Use Cat ET to perform the "Cylinder Cutout Test" in order to identify any cylinders that may be overfueled. A fuel injector tip that is broken or fractured is a possible cause of a cylinder that is being overfueled. If a cylinder is identified by the test, Remove the injector and check the injector tip for damage. Check the fuel injector tip for cracks or breakage. If necessary, replace the suspect unit injector.
Injector
Result: The fuel injector is OK.
Proceed to the next step.
Result: The fuel injector is NOT OK.
Repair: Make the necessary repairs.
If the problem is not resolved, proceed to the next step.
4. Check the Fuel Transfer Pump
A. Ensure that the weep hole for the pump is not plugged.
B. Check for fuel leakage around the shaft seal for the fuel transfer pump.
Seal
Result: The weep hole was plugged.
Repair: Clear the plug.
Result: The pump is leaking fuel.
Repair: Repair the pump or replace the pump.