I am trying to figure out a problem on a friend of mines truck 2001 cummins
and it keeps lighting his low fuel pressure warning light. we have replaced the lift pump twice and relocated the pump to the frame close to the tank to make it a pusher. still had problem ,bought a draw straw and complete big line kit and installed these and still a problem we tried different senders for the light, still have problem vehicle runs beatifully and has a lot of power especially after the draw straw install but that light is bothering us any other ideas would be appreciated we plan on a gauge this next week but we also figured that trying different sender units for the pressure would have made a difference all to no avail though. thanks in advance
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Place a regular gauge inline and see what the pressure is... Maybe just a bad sending unit?

 

I have tried 2 different senders and lift pumpsand big line kit and the same result we have tested for leaks and everything else i can think of can the vp have a bypass type leak where it is not allowing pressure to build before it?

 

If you put a big line kit all the way to the VP44, you should have plenty of pressure. I got a brand new LP that I could pull down to 2psi a couple years ago. But I doubt that two in a row could be bad. Maybe a dirty fuel filter? It's worth a look if you haven't yet. I'd put a gauge on it to be sure.