ok i have a 94 z28, it had been running fine then one day the engine cut off while i was driving and wouldnt start back up. the next day it started fine. so we checked and changed most everything in the ignition system, some sort of module and coil. as far as i can tell it runs now, if i can get it started. if i pump the gas when i try to start it, it will finally start up, but then if i turn the engine back off, and go to turn it back on, it wont. ill let it cool down for about 30 mins then sometimes it starts again. any suggestions? ive run out of ideas unless its something to do with the fuel. also the fuel pressure is fine, so i dunno, help!

 

test your evap system and the egr.

 

could be lots of things.throwing any codes?ses light?wouldnt hurt to get it scanned if possible.sounds like some of the opti issues i have had but.scan

 

I had a similar problem minus the engine cutting off while driving. When ever I would start the car it would crank over fine but when i would drive it or let it reach its normal operating temp and turn it off it would not start back up until i waited 30-45 mins. I change my starter and never had a problem since.

 

when you get it running, how does it run? you're saying when it gets warm it shuts down? is it throwing any codes?

at this point it could be lots of things...clogged fuel filter, egr system, o2 sensors(which is what i'm leaning towards). get it scanned and we can go from there

 

Sounds like the fuel pump is going...how many miles you have on the car? Turn the key on and listen for the pump to cycle. Pay attention to the pump cycling the next few times and in between try to check the pressure in the fuel rail, especially the next time it won't start. Also check the harness back to the fuel pump...had one the other day that the wires were frayed on and the starting and running was intermittent.

 

Pumping the gas pedal when trying to start a fuel injected engine accomplishes nothing, except to confuse the PCM. Scan the PCM for codes, it may give you a lead of where to look.

 

^^^ yep scann for trouble codes. usually if u have to pump or hold the thottle open to get it started then it getting to much fuel. that would point to things like 02 sensor, maf, map, egr, gas cap, evap, fuel pressure regulator. may even be a plugged cat.

 

GM puts a diagnostic system in its PCMs that will shut off the fuel injectors if it reads the throttle position at full open. This is used to troubleshoot the engine in many ways including compression testing. You should not touch the gas petal at all before the engine starts.

OK now with the problem with your car. I would be putting my money on your fuel pump. I have run into this issue many times and when you follow GM's test procedures the pump will pass every time, being an ALDL car there will be no codes. and more often than not even an OBDII engine will not pull a code here. I am going to guess that the engine will die more often when the fuel level in the car is 1/4 tank or below. This is because the fuel in the tank cools the pump and when the level is 1/4 or lower there is not enough cooling for an older pump. The bearings in the motor are heating up and then seizing the motor. After a few minutes of cooling off the motor in the pump can spin again and the pump will start working again.

The last car I repaired with the same problem cost the owner over $2000 in dealer attempts at repairing her car. Fuel filter, ignition module, new plugs and wires and a few other things they tried. The proper GM test for fuel pressure is at idle and again at 2000 RPM engine speed no load. During those conditions the pump is not working very hard and does not generate as much heat as when you are running with the engine with a load on it where fuel demands are higher. Good luck with your car and I hope you get it fixed soon.

Massey