Fuel Pressure Problem (347)

347 Pony · Feb 4, 2008

Let me start at the beginning, my car has a aftermarket fuel pump (mounted in front of the tank) and the rubber line that goes between the fuel pump and filter (1/4 inch Goodyear hose) had a split in it. I replaced the hose with 1/4 inch fuel injected hose from Pep Boys and the car fired up fine. The problem comes in when I accelerate, fuel pressure is at 40psi when idleing but under throttle I lose pressure as low as 20 to 25 psi. It has 30lb injectors and a big pump with a stock regulator, I am going to replace that to a adjustable one tonight, any other thoughts as to what it might be, the car was running great before the fuel line broke.

:SNSign:

Funanin · Feb 4, 2008

strange, but something is obviously not working right... I would do the regulator first, then if it still does it, you could disconnecting the pump and blowing compressed air in the line to make sure u get everything out in case something got stuck in there when u were tinkering. Other than that the only thing it could be is the pump is failing. The only way to check that is to hook up a scope and see exactly what the motor in the pump is doing. If there are large drops of current when the pump is on, that means the motor in the pump is going bad because its not pulling a steady current.

Have you changed your fuel filter lately? If that is clogged up real bad, that would kill fuel flow as well.

347 Pony · Feb 4, 2008

It's been a while on the fuel filter, I'll replace that too,

347 Pony · Feb 5, 2008

Ok, I went home last night and replaced the fuel filter, took the car out and it ran 200% better but was still loosing pressure ALOT slower than it was before. I fired it up this morning to come to work and now its worse than it was before the filter change and it looses fuel pressure much faster without barely giving it any throttle. It still idles normal at 40psi. Any help would be appreciated, I hate her running this way and its getting annoying getting shown up at stop lights by Honda's because I can't get on the gas.

PUNISHER RACING · Feb 5, 2008

what pump?

347 Pony · Feb 5, 2008

I'm not 100% sure its wrapped in rubber mounted in front of the tank, all I know is its, real loud, could the pump be going bad and not supplying enough?

PUNISHER RACING · Feb 5, 2008

do you still have your stock in tank pump?

347 Pony · Feb 5, 2008

I'm not sure, I've only had this car a little while and I have yet to drop the tank, it sounds like the only one running is the external pump though.

PUNISHER RACING · Feb 5, 2008

sounds like your pump can't keep up. i would suggest dropping the tank and replacing your existing pump (intank) with a 255 unit. then bypass that external thing someone put on there all together. put on your adj. regulator you said you had and set it at 42 psi with the vac. off. ( you are nat. aspirated i take it? )

347 Pony · Feb 5, 2008

yea n/a for now, 30 pound injectors

347 Pony · Feb 5, 2008

Why would it run so much better last night after the new filter was installed? Then worse today.

PUNISHER RACING · Feb 5, 2008

maybe your tank is full of crud and its plugging the sock and filters up

Funanin · Feb 5, 2008

yea drop the tank, its not very hard as long as u dont have more than 1/2 a tank. Its basically 2 bolts, but they are usually very very tight. The ones that hold the bands around the tank. If you have more than 1/2 a tank, you will probably want to siffen some out into a bucket or gas can or somthing. you might run into something lucky and have the stock pump still be in there in which you can plug it in, start the car and rev it to see if the pressure drops. If not, then its def the aftermarket pump and you should just remove it and replace the stock pump with say the $110 bbk 255lph inline pump or a walbro 255. Also obviously change the wiring so it connects back to the stock pump setup.

347 Pony · Feb 5, 2008

Thanks for the help everybody, I'll drop the tank tonight and find out whats going on in there. I'll let y'all know what I find.

347 Pony · Feb 7, 2008

Well I found out that there is a 190 lph in the tank that is hooked up and working, the pump in front of the tank was a booster pump, I disconnected that and now she runs great. I think I am going to put a 255 in the tank and let it ride. Thanks for all the help.

PUNISHER RACING · Feb 7, 2008

that 190 will work OK N/A with 30's

Fuel Pressure Problem (347)

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