78stang

hows it goin i have a 1986 mustang gt. it first started that i could get it started but it wouldnt idle and would be a real pain to get started and that any pressure on the gas it would fall on its face. so i took the injectors out let them soak in seafoam for well over 5 hours then i changed the fuel pump/assembly and the fuel filter hooked a fuel pressure guage up and it took awhile but eventually it was able to build 40 lbs. then when i cranked it, it would quickly drop to about 7lbs. the car would start for like a second but thats all. also ran a jumper wire from the battery to the pump and it did the same thing. any ideas would be awesome thank you

jojobanks

when you say it took awhile to hit 40lbs, did you check this as soon as you were done replacing the pump/filter/etc.? That would be normal since it takes a minute for the pump to fill all the lines/filter back up with fuel.

have you checked your fuel pressure regulator? Disconnect the vac line from the FPR and plug it. Then take a vac hand pump and connect it to the nipple on the FPR. with you fuel pressure gauge attached crank the engine and apply vac to the FPR and see if the pressure builds any.

78stang

we cycled the key a bunch of times before cranking it and it did it then to. but i def. will check the fuel pressure regulator thank you very much

AdderMk2

sounds to me like you have a leak inside the tank. The rubber hose that goes from the pump to the sending unit can crack, break or split open, and the only real symptoms are slow building fuel pressure, quick FP bleed off, long crank times, and lack of power at WOT.

TrimDrip

I agree with adder. Most vehicles I see with a bad pump have trouble starting at all with a bad pump but usually will stay running at idle.

Either way the tank is going to have to come off to see if it is hose or not. I would go ahead and get a hose though. If it was mine, I would do a strainer and filter too.

78stang

i did a whole assembly today with new hoses and filter and i made sure not to cut the hoses open

AdderMk2

if your pressure is still bleeding off that fast, and its not leaking out anywhere, you could have a bad pump.

78stang

the pump is brand new out of the box just installed yesterday

AdderMk2

i dont care... Ive been working in the automotive industry long enough to know that "new" does not always mean "good".

TrimDrip

it don't matter if it was new or not. I saw a new delphi pump not work for the first time a couple of weeks ago. We had the bed off the truck so we said f-it, send us the napa brand....which i guess is the same as an airtex. The truck ran with the napa brand as to where usually it takes 2-6 airtex pumps to get a good one.