[91CumminsBoy]

Hi, I have a 91.5 D250 Cummins that I've had for about 2 months now. It has a newer lift pump but someone had it wired which looks like directly to the fuse box and ignition and theres a wire I have to plug up to get full power to the ignition. But when you turn the key on sometimes the pump runs and sometimes it doesn't :shock:. The truck usually starts right up and runs great but losses power after 10 minutes of running. It's like theres a short in the lp wires and the pump turns off. Any ideas on how to wire it better maybe directly and should the lp cycle every time with the key or only sometimes...
Please Help :thumbsup: Thanks

 

[9297oldram]

Welcome

So your saying you have a electric fuel pump? If so do you have a fuel pressure gauge on it, the stock LP puts out 3-5 PSI and if you run much over 10-12 PSI you could blow out the front seal on the IP.

I would say the best way to wire it up would be using a relay so the pump always gets battery voltage. Then use a key on wire to trigger the relay such as the one going to the FSS then you will know the pump is running because the FSS will be energized and open.

 

[91CumminsBoy]

The lift pump is just the old mechanical one not electric. But it seems theres a short somewhere under the dash since the fuse box has been messed with. What is it that tells the lift pump to cycle and where is the relay located for it.

 

[9297oldram]

The stock factory LP isn't electric it's mechanical and on the drivers side of the engine right above the starter.

 

[91CumminsBoy]

Yeah thats right. I just cant figure out why the truck losses power like it's out of gas 10 minutes after running. The lift pump is newer, the injection pump was tested and has all new fuel lines. Then I try to start it up again and the lift pump will not run.

 

[9297oldram]

When was the last time the fuel filter changed, water will plug a filter as you drive and when you park it the water will settle to the bottom of the filter. Then when you drive it again the water will plug the filter again.

How does the truck start after it's sat for a few hours?

 

[91CumminsBoy]

Im not sure because it seemed to run good at first. But that seems like it might be the problem because it ran good in the driveway for a while then as soon as I got on the road a half mile later it stalled. After it sits it starts right back up. Thanks I will get a filter today and try

 

[9297oldram]

Dump the filter in a clean container so you can see if there is water in it or dirt. If you see water in it you better get a diesel additive that removes water.

 

[91CumminsBoy]

Ok ill dump it and look for water, the person that had it before me ran their own biodiesel in it but it stopped running, it must have been a bad mixture because when I got it I siphoned it all out then put new diesel in it and runs great now, but has the stalling problem probably because of the filter.

 

[9297oldram]

You could still have some sludge in the tank, it's hard to get it all out by siphoning it.

 

[91CumminsBoy]

Your right it could be, but ill start with the filter first and see how it acts, dropping that whole tank would be a pain lol.