Isx cummins lift pump

The lift pump relay should be tied to the Cummins side engine harness. Check the relay and pins for moisture or corrosion or swap it with a known good one. If the relay does have bad contacts you might consider throwing a new pump on for good measure. They don't run forever, and as with any electric motor when they get worn they draw more current. Check pin 30 at the relay and see if the voltage is still low. If it is you need to trace upstream as you have a poor connection or green wire somewhere in the power supply to the relay. Not likely a blown fuse or ECM because you stated there 10VDC there at key on.

What Model Pete are we working on?

HTH

 

The ECM does not directly power the pump. The ECM triggers the lift pump relay. If you are only getting 10 volts at the lift pump then the ecm is working, the relay is working and you have a bad power supply. Power for the 30 terminal of the relay comes from the ECM power supply harness, then goes through a 10 amp fuse. Locate and check the relay and fuse for corrosion and see if you have a good 12 volts at the fuse. They will be tied to the engine harness near the ECM. If not, you can just get battery from somewhere else and wire into the fuse for your power.

 

Any thoughts on my current situation?
2009 Cummins ISX CM871 communication error? or not?