Fuel Pressure Jumping At Idle
 

I just installed a fuel pressure gauge and I have 14psi at idle and 6psi at WOT

When im at idle the fuel pressure jumps up and down from 14psi about 2psi.
I bought the banjo bolt from diesel manor so the reading is right from the VP44.
I changed my fuel filter about 100 miles ago.

Is this normal?

Are you using an isolator? electric or manual guage?
Sounds like you tapped in right at the VP44, are you sure you tapped into the right place?


phox

im using an electric guage...here is where i tapped it

http://ramchargercentral.com/images/...efuel/fig1.jpg

Check all your grounds.


The truth is that the electric senders tend to do this and you should have probably went with a mechanical fp guage.

Try attaching a ground wire to the side of your sender by putting a band clamp around it. I did that and it fixed my problem.

Is that with an in cab gauge or a temporary test gauge? Have you tested that gauge with one you know that works and is accurate?? I see nothing wrong with those numbers and as long as you don't have some high HP requirements your VP should do fine with that kind of pressure. I get about 9 psi at idle and 7.5 at 2000 rpm's.

WHAT DOES WOT MEAN???? [duhhh]

and that's pre Holley Blue, which is going to be installed when my gauges get here Tuesday. I had my fuel pressure tested a few times since buying this truck tho I have purchased a VULCAN PERFORMANCE fuel pressure test gauge which makes it VERY EASY to check your fuel pressure at the VP. I'm glad I waited until I knew more about which kind of gauge and where I wanted it/them mounted tho driving one of these VP equipped trucks around without at least a low fuel pressure light is like driving without an oil light/gauge only a LOT more likely to fail and cost some serious $$. I had some solace in that my truck apparently already had a problem with the lift pump and got the dealer's fix known as the pump in the tank mod and while known to be weak for high HP rigs, aren't known to fail, so the pressure has been "adequate & constant" every time it was checked, tho the Holley Blue and gauge install later this week should alleviate any future worries.
Anyway, check that gauge against another you know is accurate and go from there....

its an in cab gauge. its not the numbers I was he curious about its the jumping around. Im going to move the grounds around today since I used the ground on the back of the radio (probably not the best spot)

WOT = Wide Open Throttle

I did this. I even tried it grounding it to bare (scraping) metal.




Is it not possible that my fuel pressure could be jumping around like that?

I have a vulcan big line with a stock lift pump. 14 psi at idle and cannot pull it below 10 psi at WOT. Wide open throttle. [duhhh]

Ok, so it doesnt appear to be the ground.

I would suggest gettin a MECHANICAL guage and verifying the reading. Then you will know for sure. You can use virtually any 0-15 or 0-30 psi mechanical pressure guage. Give that a try and see what it reads....(its best to run the guage out the hood, tape it to the windhield and go for a rip around the block).

thanks Dr. Ill give it a try

I just got a edge juice/attitude and it also jumps from around 15-16 at idle. It looks like my truck is jumping a bit. As long as it keeps good pressure I guess thats all that matters.

thanks for the help everyone