Cummins Diesel Lift Pump Problems

by Jeff Woodward
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Diesel lift pumps are part of a fuel distribution system. Using vacuum, they pull diesel fuel from the fuel tank and pump it to the injection pump. Fuel pump failures will stop an engine from running.


The fuel pump coupler is a gear that mates the fuel lift pump to the gear train allowing the pump to create a vacuum. The vacuum is used to draw fuel from the fuel tank. If the coupler is damaged or broken, the fuel system will not maintain the proper suction to draw fuel from the tank.


Cummins lift pumps have electronic solenoids on the back of the pump. An electric charge is sent to the solenoid to release an actuator telling it when to open and close. A shorted solenoid will cause the pump to malfunction.


Some Cummins lift pumps are shaft-driven. When the oil seal within the pump begins to leak, the pump will not operate at the correct setting. Leaking seals can be caused by ultra-low sulfur fuel or improper fuel additives not recommended by Cummins.

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