1991 Pontiac Sunbird 3.1 won't start.

[Expos]

My 1991 Pontiac Sunbird 3.1 LE convertible won't start. About 2 weeks ago, it did start and I drove it but after about 20 minutes it began to hesitate or back-fire. One time grey smoke came out of exhaust pipes but then stopped. After that one drive, it would turn-on then cut-off after 20 minutes.
Currently now, when I turn the key it almost turns on but won't. I have tried everything below.
1. I replaced the battery,
2. replaced the fuel pump,
3. replaced the fuel filter,
4. replaced the Electric Control Module Computer,
5. replaced the spark plugs,
6. replaced the crank shaft sensor, and
7. Most recently, I replaced the Engine Control Module. Funny thing is that the car almost turns on with the old Engine Control Module but with the new one it just turns.

I am missing something? (Yes it has gas). I am at a loss and would like to get this resolved. Does anyone have any suggestions? A little help please. Thank you.

 

[melsg5]

1. Are you getting a spark at the plugs?
2. Can you do a fuel pressure test?
3. Can you do a compression test?
4. Do you have any codes?
http://www.troublecodes.net/gm/

 

[92 Sunbird LE]

1) Computer and Negative grounds are clean and Tight! ( computor grounds are on a stud on on the front side of the motor somewhere)

2) Fuel Pump Relay? ( swap it with one of the other 3 on the passenger fender) when they get worn-old they work on and off)

3) Fuel Pump Regulator? ( check the rubber hose to it, if wet replace the regulator)

4) 91's Sunbirds are famous for the fuel pump wires to get corroded near the fuse box / floorboard area, Check the wiring all the way back to the the pump.

Thats all I can think of since you covered most of the stuff already.

Doug in P.R.