91 Lumina 3.1 "T" will not start

I have a 91 Lumina 3.1, engine code T, car will not start. Using Auto X-Ray analyzer, no codes from the ECM, fuel pump cycles when attempting to start, fuel pressure at the Schraeder valve, but no guage to check the pressure. Hooked timing light to all plug wires to check for spark, all seem good, should indicate coil packs are ok, have not pulled the plugs yet though. Checked resistance on the one easily accessable injector , reads 12.5 ohms.

I am inclined to think it is the ignition module, it is the first coil pack engine I have worked on. Also wondering if it is an injector issue, can one bad injector shut down the engine? I don't put a lot of stock in this because GM usually equips cars with limp home mode for this reason. I wouldn't normally think it is the crank position sensor as that should throw an engine code.

Car ran great prior to this problem cropping up, I would appreciate the benefit of member wisdom from someone who has worked through this problem before. If you reply with ideas, also include the test method, I am a competent mechanic, but not a professional and knowing the testing tricks is more than half the battle.

Thanks

Welcome to AF. Spray carb cleaner into the intake , if it starts it's a fuel problem, then check the actual fuel pressure, 37 would be about right, basic diagnostics are in order here. Crank sensor will not necessarily throw a code. If still no start then it is a spark problem and usually the module or cps is the problem, post back if the tests are inconclusive.

Sounds like we need a scanner,that will check for crank sensor but will not tell you if ICM is bad.Ohm meter,with specs,will tell you if crank sensor is good.Get out the books or head off to the shop dude.

Spark at the wires on all cylinders would pretty much eliminate the ICM and the crank sensor, as if these were bad you'd have no spark. AS Max stated, checking fuel pressure is next on the list. It is possible for the fuel pump to operate without producing enough pressure to start the car.

With the engine cranking, is there an injector pulse? Sometimes you can lay a finger on the side of the injector and feel it vibrate. You might use a long piece of fuel line hose, listen at one end, place the other end on the injector, listen for the clicking sound. You might use a noid lite to check for B+ and ground at the injector circuit, with the engine cranking.

If the computor doesn't see an rpm signal, the injectors won't work, and other than the initial prime, I don't think the fuel pump will run either.

If your interested, I believe the purple wire with the white tracer coming from the ignition module to the ecm, carries the rpm signal.

Gentlemen, thanks for your posts and the information, here's what I have found so far.

I am NOT getting any spark, my initial post was in error (too many hours worked, too damn tired). I was able to configure my analyzer to check for RPM, 0 RPM when cranking (I checked on another vehicle and my analyzer will report this when cranking). Also tried starting with starter fluid, would crank but not start.

With no RPM reported to the ECM I should have no spark, and no injector pulses or fuel pressure after the initial 2 second prime, correct? Since the RPM leads come from the ignition module via the CPS this would seem to lead to the crankshaft position sensor or ignition module itself as the bad component.

Again no codes are being thrown, is there an easy way, or any way, to test the ignition module before I pony up $200, or the crankshaft position sensor (I am working solo, which can make testing almost impossible)?

Thanks for the assist.

Mike.

On my way to autozone to test the ignition module, will let you know what turns up.

Mike.

I think your headed in the right direction. Just to add, below a certain rpm, I believe the ignition module controls spark timing not the ecm.

I'd check B+ and ground at the ignition module.

You could do an ohms test on the crank sensor. I don't have the specs in front of me.

Well autozone was not able to test the ignition module (just once I would appreciate an informed answer from a parts person on the phone), so I bit the bullet and bought one. After a PITA changing it, the car runs like a champ again.

Thanks for all your help!

Mike.