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I have been fighting this problem for a month now and i can't figure out the reason for it. I have a 84 mustang lx with a holley 650dp on a 351w with a torker2 intake and also a holley electric pump rated at 15psi with a dead head regulator set to 5.5. When I first start the car everything is fine as far as pressure goes, it runs for about 10 minutes and slowly loses pressure all the way down to 1psi. I have a clear plastic fuel filter (new) between the carb and the regulator and can clearly see there is no fuel going in it but when i take the fuel line off the dual feed line for the carb i get plenty of flow. It's like there is air trapped in it. i don't think it is vapor lock because none of my fuel lines are by the exhaust. The car has a return line that i currently have plugged off, and the tank is vented through the gas cap so i don't think that would give me a problem. i have tried mounting the pump lower thinking it might have been pulling gas out of the tank instead of having it gravity fed, with no luck. I am out of ideas and starting to think it might be a carb issue. please help me i want to drive my mustang bad !!!
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Where is your electric pump mounted? It needs to be right by the tank, electric pumps are generally pushers and not pullers. If it's in the engine compartment then it's most likely not able to pull fuel all the way from the tank. Otherwise I'd suspect the regulator.
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13.20's with 2.25-2.30 60's, 40+ year old suspension sucks!
Best trap 107.11mph, we'll see what the new intake/carb setup does.
12.80 at 110.5mph NHRA DA corrected
I have it mounted right in front of the gas tank and about 3 inches above the bottom of it. It looks like i have air in the lines with no way to bleed it out, i have been thinking it could be the regulator, but everything is new.
electric pumps will self bleed the system I have never seen one trap air in the system, check all your fuel lines and make sure they are not drawing air anywhere due to a loose clamp or a hole in the line..ie pin hole is all it'll take
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Originally Posted by dudeboy
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I think it's the pump, maybe the valve relief, all i know is i'm out of options other than to try a new pump. getting a 4-6psi carter this weekend so i don't have to use a regulator and hopefully that solves my problem
well i switched out to pump to a 5.5-9 psi unit, same problem losing fuel pressure after about 10 minutes, i have about 18" of rubber hose going from the steel line to the carb, would that have anything to do with it?
Won't be regulator if you have the return line blocked off. Check your voltage at the pump when it starts to lose pressure, make sure it's not dropping to 8 volts or something stupid, as remember, you have probably near 20 feet of wire, I don't know what size wire you used, but for that long stretch of wire I would run a 12ga wire to power it, to keep voltage drop to a minimum. When the wire heats up, voltage drops even further. You could also by-pass your fuel filter, just put a barb in temporarily and see if that makes a difference. As other than that, your fuel is boiling or you have another bad pump.
You should have a relay for the pump also. I don't think there is a problem with the regulator because the one's I've had trouble with do the opposite, fuel pressure goes up.
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no fuel pressure at carb
losing fuel pressure after about 10 minutes, i have about 18" of rubber hose going from the steel line to the carb, would that have anything to do with it?
