SPN 1347 - FMI 7 (Fault Code 281)

SPN1347 FMI7
Fuel Pump Pressurizing Assembly 1 - Mechanical System Not Responding Properly or Out of Adjustment

High Pressure Pump

Fault Code: 281
PID(P), SID(S): S126
SPN: 1347
FMI: 7
Lamp: Amber

REASON: Fuel Pump Pressurizing Assembly 1 - Mechanical System Not Responding Properly or Out of Adjustment. A pumping imbalance between the front and rear pumping plungers has been

EFFECT: Engine will not run or possible low power.

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.

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 failed, pump head drain flow will be excessive. If a seal failure 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.
A faulty fuel pressure sensor signal due to a damaged fuel pressure sensor signal wire will cause the fuel pressure sensor to be inconsistent. This condition can cause Fault Code 281 to become active on an intermittent basis.

Read More:
SPN 1347 - FMI 3 (Fault Code 272)
SPN 1347 - FMI 7 (Fault Code 275)


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