Fueling & Injection Fuel Pumps | Injectors | Rails | Regulators | Tanks

fuel pressure

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Old Feb 5, 2007 | 08:16 PM
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Default fuel pressure

how long should i maintain fuel pressure (via my rail gauge) after i shut the car off?
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Old Feb 6, 2007 | 02:09 PM
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mine starts to bleed off after a few minutes
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Old Feb 6, 2007 | 04:14 PM
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thanks dude. didnt know if that was normal or not.
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Old Feb 6, 2007 | 09:29 PM
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I assume so, mine builds up to around 70 when running and then when not after about 5 minutes it floats around 20 to 30 psi
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Old Feb 6, 2007 | 10:58 PM
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Originally Posted by WhiplashDVD
I assume so, mine builds up to around 70 when running and then when not after about 5 minutes it floats around 20 to 30 psi
70 psi? Damn...what pump/regulator are you running?
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Old Feb 7, 2007 | 07:45 AM
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Racetronix pump, hotwire kit, and stock reg. Ill have to take a pic when i can get it running again. Problems with too much fuel since pump swap.
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Old Feb 7, 2007 | 07:52 AM
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now before i look bad this was at idle when the car was running. It was more of a max pressure reading.
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Old Feb 7, 2007 | 07:58 AM
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Originally Posted by WhiplashDVD
I assume so, mine builds up to around 70 when running and then when not after about 5 minutes it floats around 20 to 30 psi
70psi on stock regulator, surely something is wrong, the regulator ment to regulate to a set pressure.

As for fuel pressure drop off, mine sits just under 60psi straight after shut off, after about 4 mins, its down to 30psi, and about about 10mins all the pressure has gone.
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Old Feb 7, 2007 | 09:03 AM
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Originally Posted by RedWS6 00
As for fuel pressure drop off, mine sits just under 60psi straight after shut off, after about 4 mins, its down to 30psi, and about about 10mins all the pressure has gone.
thats exactly what mine does. having what appears to be an un-metered air situation, have tried EVERYTHING and just reaching for some sort of hidden problem right now. thanks.
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Old Feb 7, 2007 | 09:37 AM
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Originally Posted by WS6nJAX
thats exactly what mine does. having what appears to be an un-metered air situation, have tried EVERYTHING and just reaching for some sort of hidden problem right now. thanks.
Dont think of it as a problem, its normal for the pressure to drop off when the pump isn't running. The fuel is probably going back through the regulator or something due to no pressure on the other side of the regulator as the pump isn't running after shut off.
Or am I missing sometihng here, I've probably missed the question. What do you mean Unmetered Air?
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Old Feb 7, 2007 | 10:33 AM
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long story....
did a complete top-end rebuild. heads, cam, everything. had a weiand intake on the motor and was having all the symptoms of un-metered air while trying to get a tune. the iac reading keeps bouncing up and down, do to what appears to be air entering the intake/system somehow. decided to blame it on the weiand and sealing issues. purchased an ls2/ptm combo. did the install. and i'm still having the same problem(s). when throttling up while in park, the idle hangs for several sec's. also we cant get it to idle below 1000 rpms no matter whar we do. have checked everything. i found a cracked vacuum line and repaired it. but still the problems continue. i really was just fishing when asking about the drop in engine off fuel pressure. i am at a total loss at to what else to try here.
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