MBE 900 DDEC VI Troubleshooting – Section 4.4 Faulty Fuel Nozzle/Unit Pump

Section 4.4
Faulty Fuel Nozzle/Unit Pump

To determine if a faulty fuel nozzle or unit pump is causing the cylinder to misfire, check for the following items: ‪

1. Use the DDDL 7.0 to detect any fault codes.
2. Make sure that the transfer tube thrust bolt is installed at the proper torque of 45 Nm (33 lb ft). A leaking transfer tube may be identified by cylinder cut out evaluation.

Section 4.4.1
Faulty Fuel Nozzle/Unit Pump Repair

Refer to the “Injector Unit Pump” section of the MBE 900 service manual, fuel system chapter. for unit pump and nozzle replacement.‪

Section 4.4.1.1
Verification of Repair for Faulty Fuel Nozzle/Unit Pump

Perform the following steps to determine if the replaced fuel nozzle/unit pump resolved the misfiring cylinder conditions:‪

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.‪

1. Start the engine.
2. Run the engine speed up to the occurrence of the misfiring.
3. Listen for misfiring cylinder.
   1. If the engine is not misfiring, shut down the engine. No further troubleshooting is required.
   2. If the engine is misfiring, shut down the engine and check for a faulty MCM; refer to "4.5 Faulty MCM" .