Engine/Transmission (1998.5 - 2002) Predictable but not really fuel pressure

[Jrork]

Goofy fuel pressure

Hey folks,

I have the 98. 5 listed in my signature. I've always had 13 to 15lbs of fuel pressure on my gauge but lately I noticed it would drop out of the blue down to about 7lbs. I pull over to the side of the road and shut the motor off and then when I restart, it's back up to 13 or 15lbs again.



Would this be an indicator that the ECM is going out since I seem to recall reading that it's what regulates the voltage to lift pump.



I wouldnt think it's the lift pump or fuel filter (about 2 months old) causing this problem since shutting it off and restarting often fixes it.



I'm all ears. Thanks a bunch... ..... john

 

[Jrork]

Well, swapped the filter out for grins and looked closely at the fuel I took out of the filter housing. Certainly some dirt, little bits of rusty material and some rubber like material but not horribly filthy.



I also plugged in my code reader and there's no codes listed...





I have the vulcan remote mount LP setup with the big lines.

 

[Wyomingcowboy]

How's the pressure now?

 

[Jrork]

Well, it seems good. My wife took it to the store and sent me a text that it was okay.



With that said, I'm not completely sold that I'm out of the woods yet given that yesterday I drove it for over an hour with no problems and then it started doing it consistently on the way home. This morning prior to changing out the filter it was fine.

 

[diesel DOG]

I just had similar problem. left the job and drove 3 blocks with little power. urn the truck off and it was fine when I resumed. Drove 50 miles then noticed that when on cruise the truck would lose 4 mph then kick back up on a level road. Fuel pressure gauge was not working for a while and a new one was on my seat which I never installed yet. Checked pressure and it was 7 at idle. Then checked it under full acceleration and it was 2 lb. Put in new lift pump and it has been fine for a few days and pressure is 12 while driving and at idle,

Hope my injection pump was not damaged before I fixed it but I haven't been towing or full pedal.

 

[Gary - K7GLD]

Sounds like the pressure regulator is getting erratic and flaky...

 

[Jrork]

Then checked it under full acceleration and it was 2 lb. Put in new lift pump and it has been fine for a few days and pressure is 12 while driving and at idle.

Gulp!!! Glad to hear you're back up and running. Good luck

Sounds like the pressure regulator is getting erratic and flaky...

Where is the pressure regulator on the lift pump?

 

[Jrork]

Well, here I am a month later and while coming back from a long road trip my pressure dropped to 5lbs. Pulled over and turned off the truck and then restarted it and it's back up to 14 lbs at idle and about 12 on the road. #@$%!



The fuel filter has less than 1000 miles on it and my son needs to borrow my truck. I'll just have him watch the gauge and be cautious (which I'm 100% confident he will) and I'll keep my fingers crossed. Maybe I'll swap out the lift pump when he gets back and give that a try.



Any thoughts or suggestions would be very much appreciated... ... ... john

 

[Sticks]

Time to get a FASS or some other after market pump.

Might be the ECM, might be a bad batch of pumps. I could have bought 2 FASS systems when I went through the same problem back in '04.

You could try to rig up a volt meter to the pump power wires to see if you are losing voltage while driving/pressure drops.

 

[Bessler]

I have a stock Carter That was a constant 14 psi. Then one day was running 8 psi then would come back up to 14 psi then at times would drop back to 8 psi. It works so that is now my backup pump. The replacement pump runs a constant 14 psi, so its some thing with in the pump that drops down and comes back up.

 

[rjrkihap]

4 stock Carters (2 frame, 2 under hood) all did the exact same thing on their way to failing. That's why I finally went with FASS HPFP.



Good Luck



Ron

 

[Jrork]

Sorry guys. It's been a bit and thought I would follow back up so it might help somebody down the future.

I continued to run the existing lift pump as it seemed so intermittent. If it dropped off all I had to do was pull over and restart the truck and it would be fine.

I wasn't sure what it was and was afraid it was the computer instead. I wanted to make sure I knew what it was so I left the old pump in place.

Well, on a long vacation trip it finally started acting up to the point that it wouldn't come back up after the restart thing.

Good news is that I had a brand new LP in the truck waiting as well as all the tools.

Bad news is that I was on I-5 on July 5th along with 1. 738 million other rigs. Found an exit where I could get out of the insanity so I could swap it out.

Been perfect ever since and only tool about 30 minutes to swap. Used a pair of vice grips to pinch off the rubber feed from the tank and spill less than a shot glass of fuel.