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Ooof. Talk about an industrial sized can of worms.
The 3.8 is a reliable motor, but the early to mid '80s GM Computer Control Systems aren't.
Okay, you have spark. Do you have good spark to all 6 plugs? When it "tries" to start, does it seem rough? Will it restart after it sits for a period of time, and if so, how long does it have to sit? Is it hard to start cold (after sitting for 8 or more hours) ? WHile running, does it appear that the timing could be off (rough running)?
At this age, the pressure regulator is'nt a bad place to start. You have fuel, but have you actually checked the pressure? The regulator prevents excessive pressure, but if the pump in the tank isn't holding the proper pressure, it doesn't matter what the regulator does.
The suspect items for this system are:
In Tank fuel pump
Camshaft sensor
Crankshaft sensor
Ignition Module
Ignition Coil
ECM
Checking the pump isn't too hard. If it's putting out good pressure cold, let it run for a while and then recheck it. After that, check the igitnion coils for resistance, and check check the module. Check the cam shaft and crankshaft position sensors for obvious damage or problems, and check all the wiring leading to them. There's a simple test for a bad ECM. With the car running, in park, at idle, LIGHTLY !!!!! tap on the ECM case with your knuckles or a plastic screwdriver handle. If the car stalls, the ECM is probably bad. (This test may not help in your case, since you have a no start, not a stall problem. But this test can still help identify an ECM problem, which you COULD have.) This tap test is a semi official GM devised test, for those who laugh!
The proper tests for the above items are in the service manual under the applicable sections.
GM issued a large "bulletin" in the late '80s specifically about the proper diagnosis and repair methods for this computer system. If you have a way of getting info, such as a friend at a GM dealer, it could help to ask him/her if they have a copy.
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