banditman

Went to go start my truck the other day and could not get it to fire got looking around and realized the lift pump is not working. The truck is stock and so is the lift pump. I unhooked the plug from the pump and with the key on i get 6 volts and when i bump the engine it will only go up to 8 volts. The truck only has 40,000 miles on it could that lift pump be bad already or do i have electrical issues?

AlpineRAM

The lift pump is driven by the ECM and uses pulse width modulation. Many multimeters give strange readings on this port.

If you try to hotwire your lift pump directly from the battery you can verify fuel flow with the water drain on the fuel filter.

The stock lift pumps are notoriously unreliable, a lack of fuel pressure kills injection pumps (ouch $$$$$) so a fuel pressure gauge is strongly recommended.

banditman

Ok ill try to hot wire it to see if it works.

high bid

If you have the old carter pump... please just get rid of it and replace it with something more reliable and add a fuel psi gauge to monitor things.
I've been running this pump from Standard motor products 5015553AA, 5080885AA and had good luck with constant 10-15psi
This lift pump is probably the single most important item on the 94-02 24v Cummins trucks.

KATOOM

To assure the lift pump connection wire is delivering the correct voltage, tap into the wiring and then bump the ignition key from the ON position to the START position. The lift pump should run interrupted for 25 seconds at 12 volt. You can hotwire the lift pump to a 12 volt source but you must be sure to use a relay and use a keyed source. But even at that, you'll loose the prime features so if the fuel system has any level of a leak then it will cause bad hard start issues.

Fordzilla

That reminds me of a mid-80's DeVille i once worked on in which the ECM would not deliver the initial voltage to the fuel pump to start the engine...Once it had fuel, it kept running...Instead of replacing the ECM, I wired a GM seat belt relay which used a five second on, then off sequence, in-line using a keyed circuit...Saved the customer some money on parts and earned me a lifetime customer...It may not apply in this case, but could be worth keeping in mind......Ben

AlpineRAM

I just suggested to hotwire the pump and check for flow from the water drain of the fuel filter if there is no pressure gauge and you have no other way to check if fuel is pumped or not.

I suggested this because measuring the output voltage on the "unloaded" pump output of the ECM does not give accurate results.