Cummins ISB4.5 CM2150 Fault Code: 281 PID: SID 126 SPN: 1347 FMI: 7 Engine Fuel Pump Pressurizing Assembly 1 – Mechanical System Not Responding or Out of Adjustment.

Circuit Description
The fuel pump contains two barrel and plunger assemblies; each barrel and plunger assembly utilizes an intake and outlet check valve. Fuel at gear pump pressure is metered through the fuel pump actuator and unseats one of the two intake 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 intake 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 back side 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 high-pressure plungers inside the fuel pump.

Action Taken When the Fault Code is Active
-The electronic control module (ECM) illuminates the amber CHECK ENGINE lamp and/or malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE lamp when the ECM detects that the pumping imbalance has been corrected, and the fault code is set inactive.
-The ECM will turn off the MIL after three consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with INSITE™ electronic service tool.

Shop Talk
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 malfunction, pump head drain flow will be excessive. If a seal malfunction 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 failed
-The drain flow will be excessive. This can be measured while cranking the engine.
-The pumping plungers are broken or mechanically stuck. This can be checked by visual inspection.

If the engine oil level is rising due and Fault Code 281 is active, the pump head has malfunction and must be replaced.