Fuel pressure questions

J

j_cyrus

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May 20, 2009
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On my 2002 vp truck I am using an edge to monitor fuel pressure. I got in the truck this morning and the fuel pressure was bouncing around from 8-22 psi. Usually it stays at 16-17psi. No problems driving wise, and it doesn't dip at full throttle, it stays around 15 or so. But at just cruising speeds it bounces around from like I said 8-22 psi. Is my injection pump on its way out? This thing is only a year old with about 10k miles. Its a hot rod from Industrial. Any help is appreciated. Thanks.

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Going to change the fass filters today and see if that helps. Now that I think about it it sounds like a fuel pump issue. Anyone?

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j_cyrus said:
Going to change the fass filters today and see if that helps. Now that I think about it it sounds like a fuel pump issue. Anyone?

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thats were i would start
 
changed both fass filters... it's still doing it. bleed lines? what's next?
 
Pulled the return line to perform the 5 gallon bucket test, no fuel came out.... anyone got any suggestions?
 
First of all, a mechanical fuel pressure gauge would be a good idea. Are you trying to get fuel from the return on the side of the vp44? If so, that doesn't let much fuel past until it's over roughly 14psi. Regardless, I don't see why you're worried if you're not seeing under 10psi and there's not any drive ability issues. Again, hook a mechanical gauge up and make sure it's not just the edge setup going nuts.
 
yep. VP44's aren't the smoothest running pump. Put a mechanical gauge on, or use a snubber (1/8th npt needle valve) before your pressure sensor.
 
Diesel Powered said:
First of all, a mechanical fuel pressure gauge would be a good idea. Are you trying to get fuel from the return on the side of the vp44? If so, that doesn't let much fuel past until it's over roughly 14psi. Regardless, I don't see why you're worried if you're not seeing under 10psi and there's not any drive ability issues. Again, hook a mechanical gauge up and make sure it's not just the edge setup going nuts.
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Going to get a mechanical gauge tomorrow to hook up to it and see how it does. I just don't want to ruin the pump on the truck. 8psi kinda worries me. Like I said, ill check back in tomorrow and let you know how it goes.
 
Good deal, a snubber should protect the new one. I never had one go bad without it, but I've heard others going through sending units quickly without em.
 
i guess i was wrong... put the new sending unit in, and it is going from 13-19 now... i don't know.... wtf?!
 
I feel like a dumb ass for asking... but what is a snubber? I air locked the truck last night by the way... I bled the lines and it's still doing this stupid ****. I have a feeling the Fass is going bad?
 
Stop worrying about your fuel pump(s) so much and start using Google. The world will be a better place.

Let me google that for you

Earlier you proved to yourself that electronic gauges aren't reliable. Now you're right back in the same rut again. Mount a mechanical gauge and be done with it. If there really is another issue, it's going to be pretty hard to diagnose without accurate readings.
 
Put the snubber in, didn't fix it completely, still fluxuating from 15-19. I'm convinced it's just the sensor. Going to buy a mechanical fuel pressure gauge when cash flow permits. Thanks for the help Diesel Powered.
 
I had that chip years ago n had the same problem. I put a mechanical gauge on it n I haven't had a issue since. It only bounces up u down about two psi but that's due to the lope at idle
 
I installed an Isspro EV2 fuel pressure gauge in my truck over the summer with a snubber at the port on the VP. My pressure jumps 2-6 psi all the time. I called Isspro and was told they would exchange it if I desired but that the gauge is accurate and actually the pressure changes alot more than that but the gauge isn't sensitive enough to show all the fluctuations.

Short answer, it's fine. Get used to it.
 
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