891725 Mercruiser STUD, Starter Positive

Probable Causes
Active or Logged Diagnostic Codes
Oil Change Interval
DPF Nearing 3000 Hour Maintenance Interval
Low Load Application
Leaking Seals
Fuel Injector Tip
Leakage of Fuel Return Line
Cracked Cylinder HeadRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
A. Establish communication with Caterpillar Electronic Technician (Cat ET). Check for active diagnostic codes.
Diagnostic Codes
Result: Active diagnostic codes are present.
Troubleshoot the diagnostic code 523602-0 High Frequency Regeneration code is active can cause fuel dilution. If this code is present refer to “Diesel Particulate Filter Active Regeneration Occurrence is Excessive”.
Result: Active diagnostic codes are not present.
Proceed to Test Step 2.
2. Oil Change Interval
A. The oil should be changed at 500 hours.
Oil Change
Results: The oil does not exceed 500 hours excessively.
Proceed to Test Step 3.
Results: The oil exceeds 500 hours excessively.
Perform oil sampling to ensure that fuel dilution is not flagged prior to the next 500-hour oil change interval.
3. DPF Nearing the 3,000 Hour Maintenance Interval
DPF Maintenance
Result: If nearing the 3,000 Hour DPF cleaning interval, then active regenerations (in cylinder dosing) will occur more frequently and this maybe normal.
4. Machine in a Low Load Application
A. Refer to Performance Handbook for fuel burn for this model and compare to the fuel usage in the Product Status Report.
Low Load Application
Result: Fuel dilution can occur in low load applications. Refer to Special Instruction, REHS3007, Duty Cycle of Machine Applications Requires a Reduced Oil Change Interval. In addition low load applications can result in more frequent active regenerations which can also cause fuel dilution.
5. Leaking Seals
A. Remove the injector from the affected cylinder and visually inspect the injector O-ring seals for damage.
If leakage is found and the O-rings are in good repair, there may be a problem with the injector. Replace the injector. Ensure that the new trim codes are installed. Refer to Troubleshooting, "Injector Trim File - Install" for details.
If the leakage is not located, add the appropriate dye to the fuel tanks. Run the engine at high idle for several minutes. Shut down the engine and remove the valve covers. Use a black light to check for traces of dye around each injector.
If 523602-0 Exhaust Gas Temperature : High Most Severe (3) code is present, it may cause fuel dilution. Troubleshoot the root cause of the code first.
O-ring seal
Result: The injector O-ring seal is damaged.
Replace the damaged seals. Install the injector onto the engine and confirm that the repair has resolved the problem.
Result: The injector O-ring seal is not damaged.
Proceed to Test Step 6.
6. Fuel Injector Tip
A. Use Cat ET to perform the "Cylinder Cutout Test" to identify any cylinders that may be over fueled.
B. A fuel injector tip that is broken or fractured is a possible cause of a cylinder that is being over fueled. 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.
Injector tip
Result: The fuel injector tip is damaged.
Replace the suspect injector.
Result: The fuel injector tip is not damaged.
Proceed to Test Step 7.
7. Leakage of Fuel Return Line
A. Check for fuel leakage of the fuel return line under the valve cover.
Pump seal
Result: There is fuel leakage from the fuel return line.
Replace the fuel return line.
Result There is not fuel leakage from the fuel return line.
Proceed to Test Step 8.
8. Cracked Cylinder Head
A. Look for signs of damage to the internal passages for the fuel supply to the injectors in the cylinder head. Check for pin hole leaks. Refer to Disassembly and Assembly.
Cracked head
Result The internal passages for the fuel supply to the injectors are damaged.
Repair or replace the cylinder head.