So this morning on my way to work, I noticed that my fuel pressure is reading about 1-1.5 pounds less then what it usually reads, 13psi. I also noticed that the gauge was bouncing around and the the pressure would drop to 8-9psi and then shoot back up to about 12. Any thoughts about this problem? Thanks Tye

 

your lift pump is going bad. mine did that when i first installed my fp gauge. it eventually would fluctuate really bad and then drop way down under wot. bought a new lift pump and it cured the problem.

 

yup its the lift pump, its a 2002 so it should be under warranty

 

My 2002, still under warranty, went to the dealer. They decided the lift pump was fine. I am getting 4-5 psi at WOT. They said 5 psi is fine....

I bought my own lift pump, $175 (3990105) from a local Cummins dealer. The lift pump dealer part number is 5080885AA and the cost is $352.

I am going to send a letter to Chrysler so we will see what happens.

 

Thanks for the quick replies guys. Thats kinda what I thought, but I guess I was in denial because the lift pump and Vp44 were replaced by the dealer approx 3 months and 6,000 miles ago.

 

There's been more than a few lift pumps that were bad right out of the box,
Dealer installed, or personally installed.

Doubtfull the Dealer will do anything though,
unless you can rig it somehow to only dribble for them when they do the flow test.


phox

 

Do the volume test and take pictures of it...

That alone got me a new LP at the dealer without a hassle...

 

New lift pump installed. Interesting numbers. It took me about 1 hour and the result is interesting. At idle it is 14.8, WOT 9.8. These are acceptable, but here is the thing. When I turn the key on, zero fuel pressure, but it starts fine, only thing is it takes about 3 seconds for the guage to show any pressure. When the pressure builds it goes to 4 for a few seconds, then to 8 and sits for a second or so, then up to 15 and sometimes 15.4, then settles about 14.8. I assume since it takes a few seconds to build pressure that it must have air in the line to the sender. The guage is electric.

 

you need to bump the starter to make the pump run. it will run for 20 seconds aprox. and time out.

 

Yep did that twice to fill the lift pump. After the test drive, I turned the truck off. After the restart, I get the same thing- zero pressure for a few seconds, the the pressure builds in stages. Really strange.

 

Ditto

 

I assume thats BEFORE you installed the Dr. P fuel box and injectors???

 

The Dr P box has been on for a year now, and the injectors were put in about 3 weeks ago. Anyhow I ordered the FASS II today, should be here friday, hopefully be installed by the middle of the week. The dealer called today and were going to keep an eye on it for now and see what happens.

 

The FASS should take care of most or all of your issues. Let us know how it turns out.

 

Definetly! I've noticed that with these injectors, I can pull the fuel pressure down to 5psi when I get on it hard. I actually broke the tires loose in 4th gear, going about 40-45mph trying get on the freeway on Sunday. It was an eary feeling. The wifey's eyes got the size of silver dollars!