Fuel pressure problem

Jimmysmk3

Jimmysmk3

Banned
Apr 6, 2005
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Oakhurst, NJ
I've been having a problem with my fuel pressure for some time now. What is happening is when the car is running my fuel pressure is very erratic, like it doesn't stay at a certain psi like it should. Also when i tap the throttle the pressure drops greatly probably from about 40psi to about 20psi maybe 10psi. Now with the car off, jumping the b+ and fp ports it holds a solid 42psi or so. My fuel system consists of a mk4 supra denso pump, a -6an braided line from the tank to the rail with an inline filter, stock filter not used, rc 550cc injectors, and an aeromotive regulator also fed with -6an braided line. return line is stock. I've already tried running a direct wire from the battery to the pump bypassing the stock resister box and relay to see if it was something electric wrong but it did the same thing. The only thing out of the ordinary is the fuel pump resister or the passenger side fender gets really really hot, like it could burn you. I swapped my buddy's in, but his also got hot. I'm not so sure what's wrong and I'm running out of ideas.
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
Why are you running that pump through the resistor? Have you measured the current?

If electrical is OK a pressure drop during a snap throttle test points to a restriction of some sort in the supply side of the system. Clogged filter, sick pump, plugged sock, kinked hose, anything that prevents fuel from flowing when demand goes up. It could also be why the pump current is high.
 
Jimmysmk3

Jimmysmk3

Banned
Apr 6, 2005
79
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Oakhurst, NJ
i have not measured the current yet, i was planning on doing a 12v rewire anyways. I can check the filter i don't see how it would be clogged already, also i don't think the strainer could be clogged either, as i just changed that too. I'll check the filter tomorrow
 
Jimmysmk3

Jimmysmk3

Banned
Apr 6, 2005
79
0
0
Oakhurst, NJ
well i decided to do a flow test and i tested it right before the regulator and i was barely getting any flow, so then i went to a spot right before my inline fuel filter and tested it again and got a nice full stream. so i inspected my fuel filter and the little filter inside was very clogged. so i removed that and just put it back together and it worked fine. it was a jegs brand inline, so i dont really know if the quality is that top notch. i still need to rewire the system though, it will still fluctuate at higher psi's with the stock resister. when i unplug the resistor and trigger the pump from the diag port it can hold any pressure. so all in all looks like ive got the kinks straightened out. thanks jetjock.
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
IJ.;1086998 said:
In hindsight probably a bad thing Jim ;)
Click to expand...

^ This. And use a good filter, not one of those pissy little inline things made for carbs. Since they're not designed for recirculating fuel systems they have very little capacity.

Good job on finding that btw. I'd be asking myself where that crap came from though...
 
shaeff

shaeff

Kurt is FTMFW x2!!!!
Staff member
Super Moderator
Mar 30, 2005
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I'd also be worried if that inline filter is up to the task of holding more than 6psi of fuel pressure.

For what it's worth, I had a problem nearly identical to this. At idle, the car would stabilize, as soon as I tapped the gas, my fuel pressure gauge would drop, and the car would nearly die.

It turned out that the Nitrile glove I used to block off the fuel filter overnight fell off, and a bunch of spiders crawled in the filter and made a happy little nest. I came out the next day, didn't even realize it, and that's when all my problems started. When I pulled the fuel filter off, there were bits and pieces of spider everywhere inside it! Needless to say, it was very clogged. :(
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
Good point about the pressure. From the post I assumed he used one of those aluminum jobbies with a replaceable element but I could be wrong.

Critters. Reminds me of an aircraft accident I know about involving insects and open lines. Funny how such small things can cause so much trouble...
 
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