Hey guys sorry for this not being a third-gen question, but I'm sure many of you have had experience with 3.1 L Cavaliers before, and I'm really in a jam here. I have a 1990 3.1 V6 Cavalier Z24. The car idles like crap, and drives even worse. There is a lot of surging going on at almost all RPMs. I cannot come to a smooth stop or make a smooth acceleration without this surging. I've also noticed that sometimes the car will not idle unless I rev it, and I've put it in drive and floored it and the car goes practically nowhere. I've tried just about everything. It has new injectors, a new fuel pump and filter, and a new EGR valve. The fuel pressure is only at about 30 PSI, even with the new fuel pump. I've tried pinching off the return line to test the fuel system (so theoretically the pressure should have sky rocketted) and nothing happened. That procedure more or less "bypasses" the regulator, so I know the problem isn't in there. Today the car died and would not fire back up for a while. I went under the hood and pressed the schraeder valve on the fuel rail. Nothing came out but air. Does ANYONE have ANY suggestions??? I'm in a real jam because this is my daily driver for the winter while my Camaro is resting. I don't think it will last much longer, as the problem is getting worse. Any help would be greatly appreciated. Thanks in advance.

 

X84,

I'm guessing that this is the MPFI engine, right?

If you can only make 30 PSIG with the regulator return line closed, you have a fuel pump problem. Are you positive that the new pump was the correct one, and not a pump for a TBI engine?

Another thing you can do is to flow test the pump.

 

Vader, yeah it's the mpfi engine. I guess your idea of it being the wrong fuel pump is a possibility. But wouldn't the pressure go above 30 with the return line closed even with the tbi pump? Thanks again.

 

Did you change the pump, or did a shop? Do you know if they re-used the Pulsator? Not sure if it's on Cavaliers; I assume so. The pulsator is used to "quiet the fuel pump"... and it can leak- instead of using hose clamps, it seals to the top of the pump with o-rings. If the o-rings are old, they crack- and if you re-use the old pulsator with a new pump, you can get a fuel leak right after the pump outlet! I re-used the pulsator when I changed my Firebird's fuel pump for the first time; I didn't know about the o-rings. Second time I changed the pump, I used the short piece of high-pressure hose that came with the new fuel pump, and two clamps. Haven't had a problem yet.

When I weld on my new 1/4 panel this summer, I'll have to drop the tank- and a GM-AC TPI v8 fuel pump is going in. I'm getting rid of that darn Borg-Warner pep boys fuel pump. It died once, and I don't trust it.