Well, I guess it's my turn to have a 3rd gen that won't start... While driving my 87 GTA the other night, I stop at a light, go to turn left, and the check engine and a couple other lights filcker, and I loose everything. Think maybe a battery, but it will crank like a mother...Only about 5 min from home, so I call my son, he's there in less than 10 min, crank it again when he gets there, and it starts fine. I take it home, check the fuel pressure gauge, and its at around 30-33 lbs. I start it the next day no problem. It sets for a week or so, starts again no problem. Drive it around the neighborhood, all is fine. Sets for another two weeks, go to start it, cranks like crazy, but no fuel pressure. By now I'm convinced it's the pump, even though I replaced it with a Delco unit just over 4 years and only 2500 miles ago. Get busy with a couple other things for a few days, try to see if it will start, and notice there is no check engine light illuminated with the ignition switch in the on position, even though it still cranks over no problem. Try to jump for any trouble codes, and nothing comes up, not even a 12. Can this be an ECM issue, or should I start looking for something else first? I am able to work on the car myself, but just need a little advise as to what could be causing this problem. This GTA has 75,000 miles, is equipped with the L98 TPI 350 and auto trans, a Hypertech chip, underdrive accesories, and a catback exhaust. Any help will be greatly appreciated. Thanks

If the oil pressure switch is malfunctioning it disables the fuel pump. might be a good place to start.

you also gotta remember that even though you replaced the pump it doesnt mean its good but on the other hand ive never heard of a pump working one minute and then failing the next to work again 10 mins later... id look into the oil switch as noted above, when it wont start whip out your FP gauge and test it then plus with that delco pump you SHOULD be able to hear it prime, i swapped mine out for a delco pump last year and i can hear it prime clear as a bell everytime i turn the key on

hope you figure it out

I think you're on the right track about this being an ECM problem. The fact that you have no check engine light with the key on and engine off and are unable to flash the code 12 is a red flag. I would suspect a bad ECM or an open in one of the circuits that provide power to the ECM.

If the ECM is not working properly, the fuel pump will never come on until you crank it long enought to build oil pressure (way longer than a typical crank time).

just make sure the bulb for the SES light isnt blown, i watched my friend tear up his firero lookin for a problem with the ECM turned out the bulb was shot, not hard and sounds redundant but just check since youre already on your way through

im with Greg, check the powers and grounds. a bad fuse link or bad connection somewhere can cause your problem.
when the CEL doesn't come on with the key, look for anything else that isn't working that normally does.
when its acting up, you may be able to lightly pull around on the harness and get a general ideal where the problem is.