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Discussion Starter · #1 ·
So a while ago before i parked the truck i noticed that my fuel pressure was dropping, it used to sit at 18psi at idle and was now at 15.

The fuel pump also made a high pitched whine when warm, and always after about 30min's of running as well. It was so loud i could hear it over my truck. but i would shut the truck off for about 20mins and then the noise wouldn't return until the (fass) motor warmed up again. it would be really warm to the touch.


So i changed my fuel filters, and holy crap it was now at 30psi on the my fuel pressure gauge.

At the time i was completely dumbfounded, then i remembered that the spring i bought from fass that was a replacement also was high psi when i installed it because i had to cut a few rings off of it.

So then i cut the spring some more and reinstalled, back to 18psi, however the whining continues even to this day when i have run the truck. I've devloped a sort of paranoia that i am damamging this pump, but im lost as to where to start.

I do rememeber thinking i had a 150gph spring that they gave me, assuming now that it was in error, but im not sure what to do? is there a way to rule out that the motor is warpped? or is this thing just sucking air? I still have good fuel pressure tho.

Any suggestions?
 

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I dunno. Mine makes noise. It's audible over the engine, but only if you're standing on the drivers side, at the rear door or front of the bed. It's a pretty noisy pump. I've ignored it. I can't say it was doing it on the first day, but I can say it's done it not at least 50k miles, and hasn't skipped a beat.

If it aint' broke, don't fix it... ;-)
 

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If you had to cut the spring ( altering your prev proven set up ) then something is going under.

Pump or pump motor
Or
Relief valve on vp44
 

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This won't fully answer your question but should give you a few clues.

I've never had one of their motors apart.

The regulator on a FASS is after the filter so a clogged filter loads the pump (and thus the motor) hard. They put the regulator there as part of their air separation scheme and to regulate the output pressure. It's too bad that they don't have another bypass regulator set at a higher pressure before the filter to protect the motor.

By the jump in pressure when you changed the filter I imagine that your old filter was highly restrictive/dirty so you've been running the FASS loaded for some time.

Loading the motor hard could load the bearings and will accelerate brush and commutator wear and will heat the windings.
 

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Discussion Starter · #5 ·
i suspect that when i got the fass 150 spring that it was already to high, and that my clogged filters also masked the issue,

Should i attempt to take the motor apart and look at it? Are these motors packable bearings?
 

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Discussion Starter · #7 ·

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When I got mine I think they only had a five year warranty. When mine failed after two years I contacted them and was told that they never got my warranty card. Having nothing to lose at that point I took it apart to find the internal cap screws that held the T-block together (the T-block used to be two parts) were loose which let it suck air so it could not self prime. I took the pump apart, cleaned it, and put it back together. It worked again. Mine was always loud. It being hard mounted to the frame didn't help.
 

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You say you have a "150 spring". I had called Fass and was asking what all different pressure springs they had or could supply me. The told me the 95 and 150 pumps have the same spring.
The 94-98 pump for the p7100 has a stiffer/stronger spring for the 45psi
 

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Pepsi, I would check the amp draw of the motor. I'm unsure of what that is suppose to be tho. Might be a tag on motor for that. If not contact FASS. Just like clc said if the brushes,commutator isn't right it'll eventually burn the windings and trash the pump. It shouldn't be heard over these Cummins as we all know they are loud so your FASS has to be louder then the engine.
 
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