1991 3.1 Firebird

Fuel filter has already been replace within the past 30 miles.

On going troubles, trying to chase the problem down. Well I hook my new fuel pressure guage to the Schrader valve at the back of the fuel rail. Turn the key on and the guage jumps up to 11-12 PSI. Turn the car on in idle and it goes up to 22 PSI, give it a little rev and it drops to around 20.

Now I've been told that the pressure should be around 40 - 47, is this correct, and if it is, what do you suppose my problem is? Could it be the vac line to the pressure regulator, the pressure regulator/fuel line itself, or more likely the fuel pump?

Where is the best place to check the fuel pressure other than the Schrader valve to rule out anything from the fuel rail back?

Please let me know your experiences and even better possibly answer some of my questions.

Thanks.

 

You should have close to 40 PSI at idle. Is your pressure gauge working properly? did you disconnect the vac line going to the pressure regulator before you read the pressure? Is your ECM giving you any codes? I would take a look at that regulator before anything else... an in tank fuel pump on a thirdgen is a huge PITA. Right now I don't know of any other method to check the fuel pressure other than that valve. Good luck.

 

Pressure guage is brand new as of tonight. No codes besides the dreaded 32, which has been giving me fits since I've had the car.

I did not disconnect the vac line to the pressure regulator, should I? I didn't read that anywhere.

I did however notice when I took the cap off the Schrader valve it was weeping pretty good, doesn't do it when the cap is on, so I didn't pay it any mind.

 

It sounds like your gonna have to replace your fuel pump or have it replaced. Any way it will be a huge PITA to get done.
You have to jack your car up, take off the panhard bar, drop your rearend "I didnt when I replaced mine, it just takes some shimming and shaking to squeeze the tank out". Most likely you'll have to remove your exhaust pipes. After that you just have to take the tank out and replace the fuel pump and reinstall everything. Also wear saftey glasses while doing this under your vehicle, theres tons of dirt that will get in your eyes.

 

You can crimp the fuel return line shut, and try your fuel pressure test again. With the return line shut, the pressure regulator can't function. The pump will try to reach it's max pressure - 60 PSI. If you don't see 60 PSI with the return hose crimped, the pump is definately shot; this test rules out the pressure regulator. You could also look inside the vac hose to the pressure regulator for gas, but that's more of a "stuck on the side of a road" kind of test.

If when crimping the return line shut, you DO get 60 PSI at the gauge, the pressure regulator is bad. I've changed the pump myself- twice- so I really hope it's your regulator! The pump isn't hard to change but man it's such a pain... if only I had a lift...

 

Thanks for the replies guys. I'll try that test tonight.

Yeah, Tom I am hoping it's not the pump, but don't really have any choice if it is. I don't have a lift that I have access to either and my exhaust is welded all the way to the manifolds.

 

If it is a bad pump, do yourself a favor and have a muffler shop flange the rear section of your exhaust so you can get it out of the way to do this job. Honestly, its really not that bad...put the front wheels on ramps, jack up the rear, and put stands just ahead of the LCAS. With the jack under the rearend, unbolt the sway bar mounts from the frame (best way to keep from breaking endlinks), unbolt the shocks from the rearend housing, take off the panhard at the frame, and drop the rearend down out of your way. Remove the plastic shield around the gas cap so you don't break it, get the exhaust out of the way, remove the heat shields, and unbolt the tank but don't try to remove it completely. You can get to the sending unit/pump assembly well enough without dropping the tank completley out, and screwing around with the filler neck (the real PITA of tank removal). remove the lock ring, pull the assembly out, and replace the pump. Put it back in and put the car back together. Yeah, its going to take 3-4 hrs if you have never done it before, but its not as bad as some people make it out to be. Whatever you do, PLEASE don't cut a hole in your car to get to the pump!

 

LT1guy, why raise the front? I always just raised the rear.

 

Update: Checked the fuel pressure with the return line clamped and it was the same. Fuel pump is getting changed tomorrow night, and no, no access holes.

One question. I have been driving around with the fuel pump like this for a week or so. Just to work and back, nothing major, now could this hurt anything? Of course, the fuel pump itself, but I was wondering about the rest of the fuel system. Mainly the fuel injectors.

Again, thanks for the help guys.

 

don't think it'll hurt anything.

 

Its possible to burn a piston if you run out of gas??? Isnt it??? I've heard that before from someone on the general tech board.

 

You can do it either way, but I prefer the little extra room to work...I get a little claustrophobic under cars sometimes!

You're right, its not completely necessary.

 

I don't think it could hurt anything; the only component that is hurt when you run out of gas is the fuel pump itself (which is already bad), so there should be no problem. A bad regulator can cause injector damage (a defective Holley blew the tips off of Redraif's stock injectors), but the pump won't hurt anything.

 

How'd you keep it from rolling forward?

Not sure about the burnt piston part, never heard that one, doesn't make any sense to me either.

 

I have wood spliting wedges, that are very heavy steal, I put them under my tires to keep from rolling. A stack of boards work. We used a hammer at the car show this weekend when chaning upper balljoints on my friends semi-pro hopper. Surely you have something, just look around.

Deff set aside some good time to do this, I belive it took me about 6 hours.

If at all possible, get the tank as empty as possible. I did mine with half tank of gas. IT SUCKED!!!!

Take 85coupes advice, wear glasses, safty glasses, something. Lots of dirt!!!

Also not said. Before you crack the fuel lines open, take the gas cap off where you fill up with gas, otherwise you will create a suction and pour gas everywhere. Done this twice now

 

The top, flat part of the ramp has a ridge front and back to keep the tire from moving. Its much safer than jackstands in my opinion; I have seen stands collapse or tip over, but nothing is going to tip the ramps over.

 

Ok, that makes sense, I was trying to remember what dad's ramps used to look like, seems they didn't have the hump on the back and the front one was only about 1" tall. Hate to have it roll off and hurt someone.

Oh, and I have seen them tip over before, but I think that had to do with how they we're lined up. Live and learn. Just glad it wasn't the Firebird.

 

I had a near full tank when I took mine out. Not fun at all when you are scared ****less while moving a huge explosive tank. At least the replacement tank and pump were empty. I can barely get my car on the ramps in the front but the rear is much eaiser, at least until I lower the car an inch.

 

Got her fixed. New pump did the trick. Only took a friend and myself 5 hours. Who would have thought those bolts would be rusted on that tight after 182,000 miles? Didn't drop the tank the whole way out. Removed both panhard bars, busted one end link before deciding they didn't need to come off, and dropped the exhaust. I think there are a few GM engineers that need a swift kick to the nuts, but hopefully it doesn't need replaced ever again.


BTW this new pump is really loud, both when it's priming and when it's running. Is this normal with a new pump, does it need a break in time before it quiets?

Thanks again guys.

 

All of my pumps you can here "Wrrr". Did it have a foam "insulator" on it?? Is so, that helps quite them down. If not, its gonna be loud!!

 

Yeah, we put the new foam insulator on it, wasn't as big as the original. Didn't cover up the entire pump.

Just questioning because the original pump never made this much noise. Not like I'm taking the thing back out, I'm sure I can live with it.