899912001 Mercury TAPPET, (2.996)

Probable Causes
Diagnostic codes
Event codes
Throttle signal
Decelerator position sensor (if applicable)
Power supply to the Electronic Control Module (ECM)
Injection actuation pressure
Unit Injectors
Fuel supplyRecommended 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.
Table 1
Troubleshooting Test Steps Values Results
1. Check for Active Codes and Logged Codes
A. Establish communication between Cat Electronic Technician (ET) and the Electronic Control Module (ECM).
B. Certain event codes may derate engine power. Monitor the diagnostic codes on Cat ET. Check for active diagnostic codes and logged codes (intermittent problems).
Note: Wait at least 30 seconds in order for diagnostic codes to become active.
Codes
Result: A code is active or logged.
Repair: Troubleshoot any codes before continuing with this procedure.
Verify that the repair eliminated the problem.
Result: A code is not active or logged.
Proceed to Test Step 2.
2. Check for an Intermittent Throttle Signal
A. Monitor the status for "Throttle Position" on Cat ET.
B. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed.
Throttle Signal
Result: The status for "Throttle Position" is stable.
Proceed to Test Step 3.
Result: The status for "Throttle Position" is not stable.
Repair: Make the necessary repairs. Refer to: Troubleshooting "Throttle Position Sensor Circuit - Test", Troubleshooting "Throttle Switch Circuit - Test", and Troubleshooting "Speed Control - Test".
Verify that the repair eliminated the problem.
3. Decelerator Position Sensor (if applicable)
A. Monitor the signal for the decelerator position sensor on Cat ET.
B. Verify that the signal for the sensor is stable at different set points between the low idle position and the high idle position.
Position Sensor
Result: The signal is stable at different set points.
Proceed to Test Step 4.
Result: The signal is not stable at different set points.
Repair: Make the necessary repairs and return to service.
4. Check the ECM Power Supply
A. Inspect the circuit between the ECM and the batteries for poor connections and damage. Inspect the wiring, connectors, and the power relay. Refer to Electrical System Schematic.
B. Inspect the circuit between the ECM and the keyswitch. Inspect the wires, connectors, and the keyswitch. Refer to the diagnostic functional test Troubleshooting, "Electrical Power Supply Circuit - Test".
ECM Power
Result: The circuit to and from the ECM has no issues.
Proceed to Test Step 5.
Result: The circuit to and from the ECM has issues.
Repair: Make the necessary repairs and return to service.
5. Injection Actuation Pressure
A. Check that the injection actuation system is operating properly.
Injection Actuation
Result: The injection actuation system is operating properly.
Proceed to Test Step 6.
Result: The injection actuation system is not operating properly.
Repair: Make the necessary repairs and return to service. Refer to the diagnostic functional test Troubleshooting, "Injection Actuation Pressure - Test".
6. Unit Injectors
A. Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM.
B. Perform the "Cylinder Cutout Test" in order to identify any injectors that might be misfiring.
Note: Refer to the procedure in Special Instruction, "Procedure for Troubleshooting and Cleaning the Oil Rail System for the Hydraulic Electronic Unit Injector".
Fuel Injectors
Result: The tests were successful.
Proceed Test Step 7.
Result: The tests were NOT successful.
Repair: Remove the suspect injector, and install a new electronic unit injector. Refer to Disassembly and Assembly.
Ensure that the repairs have determined the problem. Refer to Troubleshooting"Injector Solenoid - Test" and Troubleshooting, "Injection Actuation Pressure - Test".
7. Fuel Supply
Refer to System Operation/Testing and Adjusting "Fuel System - Inspect" for additional information.
A. Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only.
B. Ensure that the vent in the fuel cap is not filled with debris.
C. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
Cold weather adversely affects the characteristics of the fuel. Refer to the engines Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
D. Check the fuel quality. Refer to Systems Operation/Testing and Adjusting, "Fuel Quality - Test" for the proper procedure. Check the fuel tank for debris or foreign objects which may block the fuel supply.
E. Check the filtered fuel pressure while the engine is being cranked. Refer to Troubleshooting, "Fuel Pressure Is Low" for the proper testing procedure.
Fuel System
Result: The fuel system is NOT OK.
Repair: Repair or replace damaged fuel system components.
Verify that the repair eliminated the problem.