Fass HPFP fuel pressure low

cummins724

cummins724

BREAKING $HIT
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Apr 16, 2007
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I installed a fass 150 HPFP [pump only no filters] on my brothers truck last year. The pressure is dropping to 8psi wot now, used to never go lower than 10psi. Is there a way to adjust pressure on the old HPFP [red pump]? Is there a prescreen inside of the pump that might be getting clogged?
 
There is a spring in the pump that holds down a diaphram and maintains pressure. Get yourself a new spring from DPP and you will be good to go. There is no screen in the pump.
 
my hpfp came with a prescreen inline filter (VP44 version), if yours had one could it be clogged up?
 
I removed the bottom cover & gave the spring a stretch. It now idles at 18psi & pulls down to 5 psi wot with Adrenaline on PL03. I didn't get to check the inlet spring because I was running late for a party, but I'll check it tomorrow.
 
I removed the inlet fitting & there is no screen on either side. I removed the bottom plate again & noticed that the spring was broken. I installed a new spring which I had in my toolbox. The spring is same size, but stiffer. After installing the spring, I noticed that idle psi is at 30psi, but now it only pulls down to 15psi wot. I know the idle psi is a little high, but you guys think it may cause a problem?
 
Is it on a vp44 truck?
I always say between 10 and 18 is best!
One of our trucks starts hard with anything over 18 psi, another one works flawless with 27 psi

If I where you I would get a bit a softer spring since that seems to be th problem.
I put on a pump lik that on a 98 with only an attitude and it pulls down to 4 psi I should check that spring too...
 
12valve said:
Is it on a vp44 truck?
I always say between 10 and 18 is best!
One of our trucks starts hard with anything over 18 psi, another one works flawless with 27 psi

If I where you I would get a bit a softer spring since that seems to be th problem.
I put on a pump lik that on a 98 with only an attitude and it pulls down to 4 psi I should check that spring too...
Click to expand...

No hard start on this truck. It runs/idles smooth as well. I'm gonna order a lighter spring though.
 
there is a couple of guys on here that are running that high of pressure on vp trucks, with no problems.
 
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