I just purchased an 88 GTA with a built 350. The car looks and runs great, but I've got this bizarre problem with the engine. When it's cool outside the car runs fine. When its above about 80 degrees the car starts missing and backfiring. The hotter it gets, the worse it runs. The problem does not appear to be related to the engine temp. If the engine is hot but its a cool day, the car runs fine. One other thing. When its running poorly, if I fill it up with gas, it runs fine for a while. I can't make any sense out of it. I have noticed that when its running poorly that the fuel pressure is low (I have a gauge). Any ideas?

 

Maybe the fuel pump is on its last legs.

 

Is there any way to check that without dropping the gas tank?

 

Fuel pressure gage.

 

What should I expect to see. I've searched the boards and best I can tell, the psi should be 45 with key on, 40 at idle and 30 at wot.

 

OK, I just went out, started it and drove it around the block. I have an in dash fuel pressure gauge. At key on, nothing registers, at idle it started out at 40 psi. But after I drove it for a sec, it had dropped to 20 psi at idle, and was idling rough. When I parked it this afternoon it would barely run, and I remember that the fuel pressure gauge was really low (maybe 10?). So, based on this info is it safe to assume that the fuel pump is kaput. Is there anything else in the fuel delivery system that could cause similar symptoms?

 

Plugged fuel filter, but not as likely.

No pressure key on is the biggest indicator.

 

OK, Thanks for the suggestions. I ordered a new fuel pump and will install it this weekend. We'll see how it goes.

 

Well, it took longer than I expected, but I finally got the fuel pump replaced and that fixed the problem. I ended up having to replace the gas tank in the process. The solder joint around the filler neck was cracked all the way around. Somebody had tried to fix it with epoxy, but that didn't work at all. Now my fuel gauge isn't working. It's stuck at just below half a tank. I checked the float before I put it in the tank. I even plugged in the sending unit and moved the float to verify that the gas gauge was reading the correct values. All was fine. But when I got everything together, my gas gauge didn't work. Any ideas?