37350T Mercruiser MANDREL

Probable Causes
Diagnostic codes
ECM Flash file
Starting aids
Coolant temperature
Cooling system
Fuel quality
Valve lash
Low compression (cylinder pressure)
Individual malfunctioning cylinderRecommended Actions
Diagnostic Codes
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 between the electronic service tool and the Electronic Control Module (ECM) . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Use the electronic service tool to check for active diagnostic
Diagnostic codes
Result: There are active diagnostic codes.
Repair: Troubleshoot any active codes before continuing with this procedure. Refer to Troubleshooting, "Diagnostic Trouble Codes".
Result: There are no active diagnostic codes.
Proceed to Test Step 2.
2. ECM Flash File
A. Verify that the latest flash file is installed in the ECM.
Flash file
Result: The latest flash file is not installed.
Repair: Install the latest flash file. Refer to Troubleshooting, "Flash Programming" for the correct procedure. Verify that the repair eliminates the fault.
Result: The latest flash file is installed.
Proceed to Test Step 3.
3. Glow Plugs
A. Check the operation of the glow plug circuit. Refer to Troubleshooting, "Glow Plug Starting Aid - Test".
Glow plugs
Result: The glow plugs are not operating correctly.
Repair: Make the necessary repairs. Verify that the repair corrected the fault.
Result: The glow plugs are operating correctly.
Proceed to Test Step 4.
4. Coolant Temperature
A. Check that the water temperature regulator is operating correctly. Refer to Systems Operation, Testing, and Adjusting, "Water Temperature Regulator - Test".
Coolant temperature
Result: The water temperature regulator is not operating correctly.
Repair: Replace the water temperature regulator. Verify that the repair corrected the fault.
Result: The water temperature regulator is operating correctly.
Proceed to Test Step 5.
5. Cooling System
A. Check for an internal coolant leak into the cylinder and/or the exhaust. Refer to Systems Operation/Testing and Adjusting, "Cooling System".
Internal coolant leak
Result: There is an internal coolant leak.
Repair: Make the necessary repairs. Verify that the repair eliminated the fault.
Result: There is not an internal coolant leak.
Proceed to Test Step 6.
6. Fuel Quality
A. Check the fuel quality. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test".
B. Refer to Operation and Maintenance Manual for information on the proper characteristics of the fuel for the engine.
Fuel
Result: The fuel quality is not OK.
Repair: Drain the fuel system and replace the fuel filters. Refer to the Operation and Maintenance Manual, "Fuel System Primary Filter (Water Separator) Element - Replace" and Operation and Maintenance Manual, "Fuel System Filter - Replace".
Fill the fuel system with fuel that meets the standard in the Operation and Maintenance Manual, "Fluid Recommendations".
Prime the fuel system. Refer to the Operation and Maintenance Manual, "Fuel System - Prime".
Verify that the procedure has eliminated the noise.
Result: The fuel quality is OK.
Proceed to Test Step 7.
7. Valve Lash
Note: Excessive valve lash will cause a change in the timing of the opening and closing of the inlet and exhaust valves. Excessive valve lash can cause a reduction of the flow of combustion air into the engine. Reduced flow of combustion air will increase the fuel consumption rate.
A. Check the valve lash. Refer to Systems Operation, Testing, and Adjusting, "Engine Valve Lash - Inspect/Adjust".
Valve lash
Result: The valve lash is excessive.
The hydraulic lifter will compensate for all normal wear of the components of the valve train.
Repair: Repair or replace any excessively worn or damaged components of the valve train.
Result: The valve lash is correct.
Proceed to Test Step 8.
8. Low Compression (Cylinder Pressure)
A. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test ".
Low compression
Result: Low compression is recorded on one or more cylinders.
Repair: Possible causes of low compression are shown in the following list:
Loose glow plugs
Faulty piston
Faulty piston rings
Worn cylinder bores
Worn valves
Faulty cylinder head gasket
Damaged cylinder head
Make any repairs, as necessary.
Attempt to start the engine. If the engine will not start, contact the Dealer Solution Network (DSN).
Result: No faults found.
Proceed to Test Step 9.
9. Individual Malfunctioning Cylinders
A. With the engine speed at a fast idle, use the electronic service tool to perform the manual "Cylinder Cut Out Test". As each cylinder is cut out, listen for a change in the sound from the engine. When a cylinder is cut out, there should be a noticeable change in the sound of the engine.
Cylinders
Result: There is not a noticeable change in the sound of the engine for at least one cylinder.
Repair: Investigate the cause of the fault on any cylinder that is not operating. Investigate the cause of the fault on any cylinder that is operating below normal performance.
Result: There is a noticeable change in the sound of the engine for each cylinder.
Contact the Dealer Solution Network (DSN).