Ok, I bought this car back in the summer it has 38,000 origional miles, and was a friend of mines. It is bone stock and all origional. The car runs great for the first 20 mins then the alt voltage starts dropping, the oil gauge starts jumping and eventually the fuel pump gets loud and then quits leaving me on the side of the road! After about about 5 min it will start back up and go a little while longer. I thought the problem was the fuel pump and it was pulling the volts down, so i changed it. It didnt help the problem is still there. Is there anyone with any idea, because i don't want to just start changing parts.

The fuel gets hot.
The car will turn over just fine when it stalls but won't start.
Right before the car stalls you can see the voltage loss in the lights and the blinker and wipers slow to almost nothing.

I'm new to thirdgen.com so sorry if this isnt the right page
Thanks!

 

Is it possible the fuel tank vent is blocked and you're getting a vacuum in the tank? Not sure why the voltage issue would happen, unless the pump starts using a lot of extra power when it happens. Easy way to check would be to take off the gas cap when it happens and see if you hear any hissing or if it'll start right after taking it off.

 

Thanks! G-reg
when the car stalls the tank has a lot of pressure on it and the gas is at boiling point. I can take the cap off and the pressure is released you can hear the gas boiling. When i changed the pump and the filter the first time i checked all the lines, vent and fuel return. Also checked the charcoal filter and the sol. Between checking all that and the voltage drop i figured something has to be pulling volts from the fuel pump causing the pump to over heat and be loud. I have a gm pump ready to go in to replace the one from autozone but i need to make sure there isn't something i'm over looking.
The battery has plenty of power even on the side of the road after something has been pulling it below 8v for several mins.

Again Thanks for taking the time, I'd love to fix this without swapping parts.

 

Well, at least it sounds like you have half the problem figured out, now you just have to figure out what is making the fuel get so hot.

Are any of the fuel lines bent too close near any of the exhaust, especially up by the drivers side manifold where the lines come up into the engine bay? Or perhaps the muffler got replaced and there isn't any heat shield between that and the tank? Since you changed the fuel pump and the same thing happened, its probably not the pump even though it might be an off brand one. That would have to be one heck of a hot pump to boil even half a tank of fuel in 20 minutes, my stove can barely get a pot of water boiling in 20 minutes.

 

Ok, so i have some new info. The thermostat is stuck open, after driving it some this weekend in 30 deg. weather the temp stayed just over 100 deg. Never had a problem. Saturday I let it sit in the drive way until it reached 200 deg then started troubleshooting, found that the alt is a steady 14.3 volts. When the fan comes on( to cool the motor not the thermostat opening) and the a\c is on thats whats killing the voltage. It drops well below 10V more than enough to cause problems. We are having a little ice storm as of right now but as soon as the weather breaks i'm going to amp the fan motor and the a\c clutch coil. With the thermostat being open and the fan doing all the work plus the a\c running do you think that the low voltage could be causing the pump to get hot or just the fact that the motor ran at 200 deg this past summer. Gas boils somewhere around 110 deg so i think just not having the thermostat would cause the pump problem not sure though.
Hey Thanks G-reg! The info keeps me looking from new directions!

 

maybe bad alternator or some kind of heat short type of thing