calls

I did a search before I made this post and couldn't find anyone with this type of problem so I figured I would ask.

A few months ago after learning the HARD WAY, I installed a new set of Autometer gauges to monitor my BRAND NEW lift pump and injector pump After a month or so I had to get a new egt gauge because the other one crapped out for some reason, now 3 months later my fuel pressure gauge is acting screwy...AT LEAST I HOPE this is the case. When I start my truck the pressure jumps up to 15-16 like always no problem rite..when I start driving it drops to around 11-12 like normal..no problem rite....now the problem...I'll be tooling along when all of the sudden this stupid gauge starts jumping all over the place..I mean jumping..not moving a lil but bouncing from 10-15 then to 0..then back to 12..then it will be ok for a few miles and then DROP to 0. After a few miles it will jump back up to 11 and work fine. It's really wierd, it seems to act up more when I'm in traffic for some reason, if I'm idling it will bounce all over then drop to 0 and act like it don't work, then when I get going again it works fine. The slower I go the less pressure I have and the more it bounces, but if I'm at a steady speed it functions like there is nothing wrong.

You guys got any ideas here?

At first I thought it was the lift pump but the more I watch the gauge the more I'm leaning towards it being bad. I know it don't matter but just for info purposes there is a little over 20,000 on the lift pump and gauges.

Shovelhead

Electronic or mechanical gauge?

If Elec. sounds like the sending unit might be on the fritz.
Also might want to check for loose ground wire on the gauge.

calls

Sorry, I meant to put that..it's a mechanical gauge.

Shovelhead

Mech gauges usually have less problems.
Mine's been doing fine for over 3 years.

Check the wiring on the lift pump to make sure you have good clean connections.

ramtd02

i think your lift pump could be going.....sorry!!

gamiller31

I would definately say it is the lift pump. Mine did the same thing, started doing it in July, very erratic fuel pressure readings as you described. Then in August, every once in awhile the pressure would go to 0, and stay, causing truck to stall(my truck will not run w/out operational lift pump). After about 5 mins, pump would start working again, and would be fine for a couple days, but then would do it again. I replaced the pump, problem solved.

calls

Thanks guys, I will be going back to cummins today and let them check it out and see if they wil give me a new one.

calls

Well I went to cummins and they were pretty good about the whole thing. All they needed was the mileage, and when I bought it and they handed me a brand new one. They suggested I put an inline filter on the fuel line of 30-35 microns.

Anyone else do this?