1991 z-28; 350. Car starts fine. Begins to act a little funny in open loop. Idle seems to surge a bit. After about 35 min. it will die suddenly. Will not start up right away. When I try, it sounds like it is out of gas. After I let it set for about an hour or two, it fires up right away...sounds good. I have changed the o2 sensor, knock sensor, coolant temp. sensor, map sensor, plugs/wires are fine, new cats. I do have something going on with my vacuum though. Tried the carb cleaner test...could not find it (no obvious hiss to be heard). I am thinking it is behind the HVAC control. All the vac lines are connnected in the engine bay. When running, the service engine light does not come on. Any help would be greatly appreciated.

 

There's a clue in there somewhere.

However, I notice from your description of what you've done so far, that any troubleshooting or repair efforts having to do with fuel that you may have done, are not mentioned.


Sounds like it's out of gas = time to check your fuel system


What's the fuel pressure while all this is going on?

Changed the fuel filter?

How old is the fuel pump?

Forget the HVAC vacuum thing for the time being; it may be something wrong or whatever, but it isn't the cause of the fuel delivery problem that's keeping the car from running.

 

I'll check on this site regarding checking the fuel pressure. The fuel filter has less than 500 miles on it. The fuel pump is pretty old. What I don't understand though, and maybe someone can explain this, and that is, if it was my fuel pump or filter, why does it fire up right away after it has been sitting for a while. After about twenty minutes it starts to act a little funny...surging/running a little rough. After that point, maybe about ten to fifteen minutes later, it will die as if I turned the key off...no sputter or any sound like it is starving for fuel; it just shuts off quick. Also, no ses light. Please help. Thank you.

 

Could be a bad pick-up coil or ignition module too.

 

My gut says fuel pump.