864592T Mercruiser HOUSING ASSEMBLY, Thermostat

Probable Causes
Diagnostic codes
Event codes
Decelerator position sensor
Power supply for the Electronic Control Module (ECM)
Fuel supply
Torque converter output speed sensor
Injector harnessRecommended Actions
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load, and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.Diagnostic Codes and Event Codes
Certain diagnostic codes and/or event codes may cause poor performance. Connect the Cat® Electronic Technician (ET) and check for active codes and/or for logged codes. Troubleshoot any codes that are present before continuing with this procedure.Decelerator Position Sensor
Monitor the signal for the decelerator position sensor on Cat ET. Verify that the signal for the sensor is stable at different set points between the low idle position and the high idle position.ECM Power Supply
Inspect the circuit between the ECM and the batteries. Refer to the Electrical System Schematic. Inspect the wires, the connectors, and the power relay. Refer to Troubleshooting, "Electrical Power Supply Circuit - Test" for more information.
Inspect the circuit between the ECM and the keyswitch. Refer to the Electrical System Schematic. Inspect the wires, the connectors, and the keyswitch. Refer to Troubleshooting, "Electrical Power Supply Circuit - Test" for more information. Fuel Supply
Check the fuel lines for the following problems: restrictions, collapsed lines and pinched lines. If problems are found with the fuel lines, repair the lines and/or replace the lines.
Check the fuel tank for foreign objects which may block the fuel supply.
Check for air in the low-pressure fuel supply system. Determine whether any of the following procedures have been performed:
Replacement of the fuel filters
Service on the low-pressure fuel supply circuit
Replacement of unit injectorsNote: A sight glass in the low-pressure supply line is helpful in diagnosing air in the fuel. For more information, refer to Systems Operation/Testing and Adjusting, "Air in Fuel - Test".
Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again.
Purge air from the low-pressure fuel supply circuit. Refer to Operation and Maintenance Manual, "Fuel System - Prime" for the correct procedure.
Cold weather adversely affects the characteristics of the fuel. Refer to Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
Check the fuel pressure during engine cranking. Check the fuel pressure after the fuel filter. Refer to Systems Operation/Testing and Adjusting, "Fuel System" for the correct pressure values. If the fuel pressure is low, replace the fuel filters. If the fuel pressure is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve. Torque Converter Output Speed Sensor
Monitor the signal for "Torque Converter Output Speed Sensor" on Cat ET.
Verify that the signal for the sensor is stable at different set points between the low idle position, the high idle position, during stall.
If the signal is unstable, verify that the speed sensor is adjusted correctly and troubleshoot the wiring. Make any adjustments or repairs necessary. Injector harness
Inspect the circuit between the main engine harness and the injectors. Refer to the Electrical System Schematic.
Inspect the 12 pin connectors, wires, and individual connections at each injector. Make any necessary repairs or replacements. Refer to Troubleshooting, "Electrical Power Supply Circuit - Test" for more information.