HydraulicGuy

This topic has been hashed and re-hashed a million times, and here is another. My third lift pump seemed as if it was failing last week. My fuel pressure dropped down to around 6-7 psi while driving down the road the other day. I pulled over and checked my gauge under the hood to compare with my in-cab gauge, unfortunatly it read the same. I shut the truck down and re-started it and wa-la, shot back up to 14-15 psi @ idle. Took off down the road again, 2 - 3 miles later back down to 6-7 psi. I bought a new LP at my local Cummins dealer and installed but now the idle pressure is about 13 psi but drops down to 8-9 psi cruising on the highway. WOT it will drop to 5-6 psi. I dropped the tank last night and checked for obstructions, lines are clear, tank is clean, I even disassembled the unit that sits down in the tank (not sure what you call it) but it has a strainer in it, all clean. Any ideas?

Thanks!

HP Upgrades

Where do you read your pressure from? If you read it from after the filter you could have a clogged filter. I would change it just to eliminate that as a potential problem.

Yes the lift pump could be going out, which is why I am installing a FASS system on my truck. On my 2nd lift pump and I dont want this issue again, plus I will be installing more HP goodies that will only draw my pressure down if I leave the lift pump stock.

Is your gauge mechanical or electrical?

Clunk

The fuel line quick connect at the lift pump might be allowing air into the pump and lines. I'd try cutting the quick connect off and connect the plastic fuel line to the lift pump fuel line with rubber fuel line and clamps from your local parts store.

HydraulicGuy

I'm reading pressure before the filter. I installed a new filter when I put the new lift pump in, it needed it. As far as my gauges, they are both mechanical.

HydraulicGuy

That's a possibility, I'll take a look at it this weekend. Thanks for the info.