Ok i got in my truck this after noon and the gauge read perfect 15 psi, i dorve it around for 1/2 hr and then came back to the house. I got in it a few hrs later and i drove about 15 miles away and about a mile from where i was going the gauge went to 0 psi then back up then to 6 and thats where it stayed till i shut the truck off for a few hrs. I got back in it around 700 and drove another 15 miles to my girl friends and the gauge was reading 6 psi but it was "sticky" when the needle would move. Now after being there for about 4 hr i got back in the truck and came home (about 30 mile trip) It didn't move off 0 after i started it up, i tapped on the gauge and it started to move back to normal pressure and it stayed normal for a minute and then it went back to acting funny and fluctuating alot. at first few miles home the gauge would do its normal thing while driving but when i slowed down the psi would go down then back up. To make it short...the gauge ended up running between 0 and 6 psi drivng home. i parked in the driveway and the pressure went back to normal again. I shut the truck off and bumped the starter and the lift pump gave good pressure. the needle is still "sticky" all the way home tonight and when i bumped the starter in my driveway. I checked my connection to the LP but i'm gonna double check it tomorrow morning when i can get it inside, the pump makes the noise it should so it is working, and i checked for any codes and got nothing. I am thinking maybe the gauge is bad, it is mechanical and i don't have a needle valve (shame on me) inline with it. The gauge is plumbed in via the test port on the VP44. I know it is possible but i don't think it is, but my LP is less than 10,000 miles old. I replaced it 4 months ago when my old LP was only idling at 11 psi and i didn't wanna risk it going at the bad time. I would greatly appriciate any suggestions or knowlegde you guys and or gals have. It just boggles my mind with this gauge.
Thanks,
matt

PS i'm gonna upgrade to a FASS sometime this spring when work picks up.

 

When my last LP went out, the gage would go from 2 to 12 psi just by punching the go pedal real fast. With the FASS II, I've never seen it below 14.

 

I just put a new one in yesterday got it warenteed from napa. only 2000 miles on it and it idles at 7psi then down to 2 or 3 under load. but when started it would be at 15 till u drove it. checked it with my snap on fuel psitester just to make sure i trust that more than the gauge in the truck and the same. its possible its bad. I would check it with a known good test gauge to be sure.
Jon

 

Get a FASS II and forget about fuel pressure problems.

 

Well my gauge isn't dropping alot like that when i punch it. Under light throttle it will go down. It would even go up under throttle. I am going to get fass 2 at some point soon. but it acts like it is possesed.
matt

 

I put my spare lift pump in place of the new one on the truck and it solved all my problems. So i went to cummins this afternoon and got a new one free of charge and just got done putting it in. I figured it was the guage from the way it was acting, Oh well. At least i caught and did something before it made things worse. You learn something new about these crappy lift pumps everyday. Looks like a FASS 2 will be finding it way on my truck in the new future.
matt

 

Some have found the quick connect fitting from the banjo/fuel pump inlet line to the supply line from the fuel tank leaking air into the system and have solved it by cutting out the quick connect and installing a piece of rubber fuel line & clamps.

 

How long has it been since you changed the fuel filter? I would check there first, it cant hurt.

We have several customers with the FASS II pump and they are loving them. Not only will you get the proper volume of fuel, but you get the pressure that will keep your injection pump alive and well.

 

I just did a service on my truck a week ago, so everything is fresh. it ended up being the pump, i have a new one in and my idle is 15 psi and if i'm lucky i get it to 10 psi WOT. My fuel milege went up just a bit too after getting that bad lp out.