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Fuel Pump Pressurizing Assembly 1 – Mechanical System Not Responding Properly or Out of Adjustment
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Overview
| CODE | REASON | EFFECT |
| Fault Code: 281 PID: S126 SPN: 1347 FMI: 7 LAMP: Yellow SRT: |
Fuel Pump Pressurizing Assembly 1 – Mechanical System Not Responding Properly or Out of Adjustment |
Engine will not run or possible low power. |
 High Pressure Pump
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Circuit Description
The fuel pump contains two barrel and plunger assemblies; each barrel and plunger assembly utilizes an inlet and outlet check valve. Fuel at gear pump pressure is metered through the fuel pump actuator and unseats one of the two inlet check valves as the fuel at gear pump pressure enters the pumping chamber. As the pumping plunger begins its upward motion, the pressure in the pumping chamber increases rapidly and the inlet check valve is closed. As pressure reaches accumulator pressure, the outlet check valve is opened. As the plunger travels upward, fuel exits past the outlet check valve and pressurizes the fuel rail.
Component Location
The fuel pump is located on the backside of the gear housing. The barrel and plunger and check valve assemblies are part of the fuel pump head sub-assembly.
Conditions for Running the Diagnostics
This diagnostic runs continuously when the engine is running.
Conditions for Setting the Fault Codes
This fault code is set active when a pumping imbalance is detected between the two high-pressure plungers inside the fuel pump.
Action Taken When the Fault Code is Active
- The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
Conditions for Clearing the Fault Code
When the ECM detects that the pumping imbalance has been corrected, the fault code is set inactive.
Shop Talk
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM. Refer to Procedure 019-032 in Section 19.
Fault Code 281 will most likely come active while operating at a steady state loaded condition. At this condition, commanded fuel pressures are highest and the pump’s pressure balance is affected the most.
If a high pressure seal has failed, pump head drain flow will be excessive. If seal damage has progressed far enough, the engine may not start because of an inability to develop fuel rail pressure.
If the engine will not start, there are two indications that the pump head has malfunctioned:
- The drain flow will be excessive. This can be measured while cranking the engine. Use the following procedure in the ISC and ISL CM2150 Service Manual, Bulletin 4021569. Refer to Procedure 005-227 in Section 5. Use the following procedure in the ISLe CM2150 Service Manual, Bulletin 4021630. Refer to Procedure 005-227 in Section 5.
- The pumping plungers are broken or mechanically stuck. This can be checked by visual inspection. Use the following procedure in the ISC and ISL CM2150 Service Manual, Bulletin 4021569. Refer to Procedure 005-227 in Section 5. Use the following procedure in the ISLe CM2150 Service Manual, Bulletin 4021630. Refer to Procedure 005-227 in Section 5.
If the engine oil level is rising due to the oil and Fault Code 281 is active, the pump head has malfunctioned and must be replaced.
Refer to Troubleshooting Fault Code t05-281
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