BryanC

I replaced my VP44 about a month ago and since then I installed a fuel pressure gauge from Gino's garage, it is the glyserin filled test guage they sell with the shrader valve hook up and needle valve also it has the 4' 250 psi hose, they say it is not for extened use but reading some of the fourms people say they run this as their guage, my problem is this I did not replace the lift pump as it was only one year old and when I put the guage on it I was getting 12 to 15 at idle and around 10 psi running 70 mph it was steady for about two weeks, this morning when I went to work it was 3 degrees out and my guage started to bounce from 15psi down to 5 psi back to 10psi and then back up to 15psi and has been repeating this all day, could this be snubber issues or fuel issues or what???

All comments welcome...

Thanks

carl48

bryan first of all that is not the gauge we use. it was MRG-1561 for $19.95 it is no longer listed in geno's. go back and get the BF-tapped for $7 and AM-3279 for $26.95 next go to autozone and get a oil pressure gauge installation kit. get the one with the copper line. it is $9 and has all the fittings needed. install the bolt and connect the snubber. connect the line and then your gauge. the line will buz if you do not place the snubber on the bolt. as far as the swing in psi you may have a pump going bad

KATOOM

Doesn't sound like a normal issue but also there's no way to tell unless you get another fuel pressure gauge to verify. Unfortunately thats the only advice I have unless you feel like spending money replacing parts until you find the problem.

DodgeRam24V

i notice my gauge fluctuating at times when it is super cold, to goes away. i suspect my relief spring in the pump is bouncing, it only varies 2 PSI and goes away when it warms up.

when had a S/W 25 PSI gauge that thing would drive you nuts, rattling, bouncing, it was the gauge. i put in a 100 PSI Ispro gauge, problem solved.

i use no snubber, no isolator, just a #4 JIC line straight to the gauge.

PS, the Stewart Warner gauge did not do that new, after it was used for a few months. i replaced it and the second gauge did the same thing, that is when i went a different route and solved the problem.

dhughe2

I just went through some fluctuating fuel pressures too. Had a Holley Blue on the rail and when it was cold enough for grid heaters, their cycling would suck my fuel pressure down at the same time as the lights etc. It was running at 11-12 psi at idle during warm temperatures. In the cold, it would run at 6 psi at idle, and each cycle of the heaters would draw it down to about 3-5. When they cycled off It would go up to 6-7 again. When I would take off, it would be running at 6-7 for a few miles, and maybe 5 miles from the house for no reason it would bounce up to 11 at idle and about 9 at cruising speeds.

I got sick of this fast so I bought a DDRP. I also needed to buy a set of deutsch connectors because the original LP connector had been cut off previously. I suspect that time, dirt, debris, a failing holley and a poor connection were causing my issues. Since I replaced with the DDRP and a more secure connection I have a solid 21 at idle and it draws down to 16 if i'm on it.

Check to make sure that your connections are solid and the rubbing hasn't exposed any wires along the line.

phal

I have an Isspro electric and my bounces from 15 -20 psi constantly.
I was thinking that I have an air leak or something and was considering replacing all my lines back to the fuel tank to try to fix it.
Something will be done this summer about it.
...gary

nickg

if you dont have a needle valve or snubber or the sender is mounted on the VP, its only a matter of time before the sender fails. before replacing lines you could add a chunk of clear fuel line on the return line to see if you see air bubbles this would indicate air leaks.

also ddrp are well reported to be not that good and they have a higher fail rate as well, so your gauge very well maybe accurate

KATOOM

It would depend on what kind of bounce you're talking about. A constant fluttering fluctuation between 15-20 may indicate that you're simply reading the VP's pulses and you need to either relocate the sender farther from the VP or try a snubber valve. But if the bounce is slower and erratic then I'd look at possible sender issues or that the fuel pump is having issues. Air in the lines wouldn't cause what your problem. Air would definitely give false readings but mostly just inaccurate.

phal

I bought an install kit and the transducer is mounted on a rubber line that is screwed into a banjo tap at the inlet to the pump. this line extends nearly all the way to the firewall and is tied off (I believe at the brake master cyl.) and the transducer is there.

I will try the clear line to see what I get.

Thanks Nick...gary

Shovelhead

This is the needle valve on my '99.
The needle valve is only open about 1/4 turn to prevent the VP pulses from making the mechanical fuel gauge 'buzz'.
This setup has been working without a hiccup since Jan 2000.