Puke

98, 24V. Guage is saying 11-12psi at idle.
I've replaced the fuel filter (I've converted this filter system to the one with the screw on filter like the mid 90s cummins had), I've replaced the overflow valve. AND..I've installed 2 new lift pumps.. I am now to the point that it must either be a guage problem. Pressure does read a little lower on a hot day and a little higher when it's only 75.. Or would it be my intake sock or screen? Does anybody know of any other thing between the tank and the vp44 that could affect pressure? Anybody have any ideas?

BigIron70

What does the pressure read at WOT under full load? Does it drop under 5 PSI? Did you Check the flow rate? Lift pump replaced with factory or after market? In tank pump or external?

Greg Reed

What kind of gauge do you have? I had an electric digital. and when the sending unit started going bad, the pressure fluctuated. I've heard of mechanical gauges going bad when not used with a snubber. I switched to a mechanical, and the needle valve opened a bit too far and the gauge needle started vibrating and making a buzzing sound. I've read where that can wipe them out. If you can get ahold of a test gauge, hook it up and compare the two.

Puke

My guage is an old fashioned oil-filled type, mechanical. It is attached to the VP side of the filter. I have NEVER in my whole life done WOT and I don't tow... basically pretty mellow driving.
The guage is inside the engine compartment, so I don't see it while I'm going down the street.

If I have my son step on the accellerator and keep it a bit above 2k rpm while I watch the guage... The pressure drops a couple pounds as would be expected. The reason I don't have an electronic guage is I don't really trust the sender... And (at least up until now), I've never seen an old fashioned guage go wrong. Last winter we had 3 or 4 days where it got below zero here, which is quite uncommon... Maybe that did something to the spring in the guage...I don't know. I may see if I've got a cheap pressure guage in my pile-o-crap , and put it on there to see if it reads the same.
By the way, my lift pump is a factory carter, mounted in the engine compartment,..I'm probabaly on my 5th one at least. I've never pulled a tube off the pump to see the flow rate..not really interested in that kind of mess.. And, if I install 2 lift pumps a few weeks apart,..and they both read the same (only not 14 like all the others),...It's hard to keep thinking it could be a lift pump... It would be awfully hard to make two lift pumps the exact same amount of "wrong"..if you know what i'm saying. Every other lift pump in the past has read 14 psi when new,.. And then the pressure went to hell MANY MANY MILES later...Gradually.
Gee, I actually might even have a test guage somewhere,..I have no idea where it would be. I've got a kit somewhere (for gassers mostly) for testing fuel pressure.. I think it goes from 0 to 100psi. I know it goes way past 30.

Greg Reed

An oil filled gauge probably wouldn't show the needle vibrating like a non oil filled type.
Genos Garage has a fuel pressure test gauge kit. The hose should be long enough to run the gauge up to the windshiield or rear view mirror to test pressure while you are driving.

Puke

There is no vibration at all in an oil filled guage.

AlpineRAM

Remove the gauge and verify it with a known good tire pressure gauge.