879172091 Mercruiser CAP

Recommended Actions
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine idle, full load, or a specific operating temperature. Troubleshooting the symptoms under other conditions may give misleading results.Diagnostic Codes and Event Codes
Certain diagnostic codes and/or event codes may cause poor performance. Connect the Caterpillar Electronic Technician (ET) and check for active codes and/or logged codes. Troubleshoot any codes that are present before continuing with this procedure.Note: Although a sensor's signal may be in the operational range of the sensor, certain failure modes of a sensor may produce an output signal that does not represent an accurate measurement. Use Cat ET to check that the pressures and the temperatures are fluctuating normally. Also check that the values are reasonable for the conditions that are present.Cold Mode Operation and Cold Cylinder Cutout
Use Cat ET to verify that the engine has exited cold mode. Cold mode operation may cause a slow throttle response. Some engines use a feature such as the cold cylinder cutout in order to warm the engine during cold mode. Again, ensure that the engine has exited cold mode operation.Flash File
Verify that the latest flash file has been installed into the Electronic Control Module (ECM).Throttle Signal
Monitor the status for "Throttle Position" on Cat ET. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed. Refer to the appropriate diagnostic functional test for your application:
Troubleshooting, "Throttle Position Sensor Circuit - Test"
Troubleshooting, "Throttle Switch Circuit - Test"
Troubleshooting, "Speed Control - Test"Injection Actuation Pressure
Check the engine oil level. Engine oil supplies the injection actuation pressure circuit. The engine oil must be kept at the proper level for fuel injection.
If service has recently been performed on the engine, air may be present in the injection actuation pressure circuit. Allow the engine to fully warm up and operate the engine under load in order to purge the air from the injection actuation pressure circuit.
Check the injection actuation pressure. Refer to the diagnostic functional test Troubleshooting, "Injection Actuation Pressure - Test".
Check the operation of the injection actuation pressure control valve. Refer to the diagnostic functional test Troubleshooting, "Injection Actuation Pressure Control Valve Circuit - Test".Electrical Connectors
Disconnect the J1/P1 and J2/P2 ECM connectors. Inspect each connector for moisture and corrosion. Also, inspect the harness and connectors for the unit injectors from the ECM to the valve cover. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".Unit Injectors
Use Cat ET to perform the injector solenoid test in order to determine if all of the injector solenoids are being energized by the ECM.
Perform the cylinder cutout test on Cat ET in order to check the performance of each cylinder. Refer to the diagnostic functional test Troubleshooting, "Injector Solenoids Circuit - Test".Intake Manifold (Boost) Pressure Sensor
Monitor the status of "Fuel Position", "Rated Fuel Limit", and "FRC Fuel Limit" on Cat ET while the engine is operating under full load. These parameters should agree with the information below.
Table 1
"Fuel Position" = "Rated Fuel Limit"
and
"Fuel Position" < "FRC Fuel Limit"    If "Fuel Position" equals "Rated Fuel Limit" and "Fuel Position" is less than "FRC Fuel Limit", the electronics are operating correctly. Otherwise, proceed with the next Step.
Monitor the status of "Intake Manifold (Boost) Pressure" and "Atmospheric Pressure" for normal operation on Cat ET. When the engine is not running, "Intake Manifold (Boost) Pressure" should be 0 kPa (0 psi).Air Inlet and Exhaust System
Check the air filter restriction indicator for a plugged filter. If necessary, service the engine. Refer to the Operation and Maintenance Manual.
Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Testing and Adjusting.Fuel Supply
Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only. If necessary, add fuel to the fuel tank. If the engine has been run out of fuel, it will be necessary to prime the fuel system. Refer to the Operation and Maintenance Manual.
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 debris or foreign objects which may block the fuel supply.
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.
Prime the fuel system if 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. Refer to Testing and Adjusting.
Check fuel quality. Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold weather operation.
Check the filtered fuel pressure while the engine is being cranked. Refer to Testing and Adjusting 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. Refer to Testing and Adjusting.