bigchief

my cars fuel pressure is too low, its around 22psi when the car is off, after i prime the pump. the pressure holds at 22psi after the pump is primed. if i start the car, it still stays around 22-25psi. this is too low, i know this, for my car, it should be ATLEAST 40psi. i clamped the fuel return line (the smaller one) in the engine bay, primed the pump, and the pressure shot up to 41 psi. any idea's? any other tests i can do to find the problem? thanks! you guys rock

3.8TransAM

22-25psi running is too low.

Should be about 43 with the vacuum line off while running and roughly 38ish with the vacuum line on while running.

Sounds like u just have a pump going south.

Prime it with the return line blocked off and than seal the inlet as well. Least check for leaking injectors while your doing it(doesnt sound like an issue at this point)

When regulators fail the pressure usually sky rockets since it pushes the diaphragm down and pours fuel into the plenum.

Side note. After doind some more testing, check the actual voltage at the fuel pump with the car running and key on, any significant drop can seriously reduce pump output.

later
Jeremy

Vader

If you can make 41 pounds with the return line clamped off, you need to look at the regulator.

bigchief

the thing is, i changed the regulator kind of recently.... i think its the pump to be honest.

3.8transam, as for sealing the inlet. what do you mean? are you saying i should block the fuel intake line as well as the return line??

vader, are there any other tests i can do to make sure its definetly the regulator??

bigchief

anything guys???

Elephantismo

Remove in the main inlet line from the rail and put a guage right on the end of it. If it reads over 42 psi you're cool, but thats on the low side of acceptable.

judgin by the fact that the pressure comes up to 41 psi with the regulator blocked off... id have to say thats the problem. Those regulators have a spring loaded disc, if that spring goes bad(or falls out like mine did) the car will hold little to no fuel pressure and capping off the return line will eventually make the pressure come back up to the pumps maximum. The pump may be going bad as well. My car held over 50psi with the return line capped a new fuel pump and a bad regulator. I would prolly change the FPR right off in your case. If the car sat after doing the job, it could have killed the rubber diaphragm. Its also possible that there is debris under the disc causing the problem. Maybe junk off the previous FPR? Check out the FPR.

eddie89TA

if it turns out to be the fuel pump. if possible use a lift, to remove the tank... i did it in a drive way once....(cruel and unusual punishment).

Elephantismo

agreed. try to get a lift. the first time i did it was a solo job took 8 hours all kinds of concrete burn. Second time i asked a fried to help, took 3 hours.. painless.
I did it without removing the rear axel both times, and i had to cut my exhaust to get it off(all the books say to remove the rear axel). You shold be able to do the same. If you need a bit of a walkthrough, just take some pictures of the rear area under the car and if its similar enough ill try ot help ya out. Gm used a few different rear ends under these cars and i dont know how they differ.

bigchief

yeah definetly, i've removed it once, it was a hella problem, i did it with the exhaust still on, in a driveway and i ended up bending the nozzle, when it was out my dad welded it where it had cracked, but when we put it back in, we realized that we welded it crooked and had to bend it back anyway, and broke the seal we had just made....... BIG headache. i plan to learn from past mistakes and REMOVE the exhaust this time around, but im doing the rear end too, so it should be easier since the rear will be out as well, so i can just slide out the exhaust

bigchief

i noticed a drop in fuel pressure a while ago with my car, instead of in the 40psi range, its in the mid 20psi range.... i've tried different things but i havent been able to find the problem, today i did one of the most obvious things.... CHECK THE VOLTAGE AT THE PUMP lol. i took a volt meter, pulled down the back seat, pulled the harness out of the trunk, and checked the voltage at the harness after i disconnected it. it did NOT read 12v, it was more like 7 or 8 volts.

there are three wires comming out of the connector, a BLACK wire, a WHITE/BEIGE wire, and a PINK wire. i traced the BLACK wire to a ground under the drivers seat, i believe the WHITE/BEIGE wire goes to my MAF BURNOFF RELAY, and i tried tracing the PINK wire, but it goes into the harness under my dashboard, and i cant see where it goes. does ANYONE know the EXACT route that PINK wire goes??? i need to see if it is crossed with another wire somewhere, or if it is burnt.

i appreciate any help any of you guys can give, thanks so much.

eddie89TA

could be fuel pump relay, dont know location of it off hand, a quick search should find it though. but most likely its the pump. but try the eazy one first.