I'm lost now. I'm usually pretty good with figuring out problems with cars but this one has my butt beat. 91 GP with a 3100. Not starting. at first it would backfire but wouldn't start after putting new heads on it. New coil packs and a new fuel pump later (fuel pump crapped out right after the coil packs were replaced) it's not even trying to fire. It's getting spark and it's getting fuel but it's just not firing. Any ideas? It's a buddy of mine's car and I'm tryin to help him out as much as I can but I'm lost this time.

EDIT: He just sprayed starter fluid in the throttle body and got it to backfire again just for a second. that tells me not enough fuel pressure. IIRC early SFI setups required 36-48 psi on the fuel to work but he doesn't have access to a fuel pressure meter at the moment and I'm 200 miles away and so my tools are useless.

_________________


98 GTP (RIP 11-5-09); 73 Z28 Camaro (350, TKO 600);01 Monte Carlo SS (L36, L67/L32 hybrid in the future)
"Death smiles at us all; all a man can do is smile back"

If it is a '91, I can assume that it is the 3.1 MPFI engine. The 3100 SFI V6 was not introduced until 1994. This being the case, I would check the timing chain. If you can see the front rockers when you remove the oil cap, remove the oil cap, and turn the car over, and see if the rockers move. If they do, OK. If not, you have either a broken timing chain or a broken cam. The latter is more common than you would think, and could cause the problems you describe. The backfire is cause by improper timing, not a lack of fuel pressure, more often than not.

_________________
One Big Ass Mistake America

Got another load of info. My buddy's idiot stepson put the plug wires on backwards. now it's starting but not staying on. It dies pretty quick. Any other ideas? I'm thinking a vacuum leak now. Speed density motors are more sensitive to vacuum leaks than MAF based motors IIRC. Could be wrong but that's just from my experience. He's looking for a vacuum leak in the morning per my advice just seeing if you guys have any more advice. Thanks guys. there's a reason I come here first for grand prix advice. y'all know your shit.

_________________


98 GTP (RIP 11-5-09); 73 Z28 Camaro (350, TKO 600);01 Monte Carlo SS (L36, L67/L32 hybrid in the future)
"Death smiles at us all; all a man can do is smile back"