88 Buick Park Ave 3.8- NO SPARK

[433red]

My daughters 88 PA has lost all spark several days after an alternator replacement. Everything was fine (no codes or warning lights) up till the point it died. What I found has me thinking an ECM/PCM failure has occured. Looking for any input to support or defeat my theory prior to purchasing anything for this aging beast.

Upon inspection at the alternator I found the battery wire terminal "floating" loose, caused by a cross threaded nut leaving a wide gap between the nut and the alternator. Kowing how sensitive the ECM/PCM is to voltage spikes or fluctuations I'm concerned the loose wire terminal is a contributing factor to this issue... Coil pack has voltage when the ignition is on, fuel pressure is good but no spark. Have yet to check the crank trigger. What is the suggested method to verify the magnetic pulse from the crank trigger? Where is the best location to verify pulse? How can I verify if the ECM/PCM is OK without involving a dealer? Any links or suggestions where I can find a schematic for the ignition circuit found on this 88 Buick 3.8?

[INF3RN0666]

Those are some tough questions man. For the diagrams you want, you'll need a Haynes manual. I'm terrible with car electrical systems because I don't understand them well. BUT, check your ground cables first and make sure the battery has about 12.5 V charge. If the battery is putting out anything less than 12.25 volts, then it's basically almost dead.

[UncleBob]

what you really need to accurate test the crank trigger is an oscilloscope. Its a square wave patern, and it may still be switching, but if the square is no longer square, you won't see it on a multimeter. If it completely dead, of course, you could see that on a multimeter

[433red]

Originally Posted by UncleBob

what you really need to accurate test the crank trigger is an oscilloscope. Its a square wave patern, and it may still be switching, but if the square is no longer square, you won't see it on a multimeter. If it completely dead, of course, you could see that on a multimeter

Any input on what the minimum voltage of the square wave could be?? Thx for the reply.

[maxwedge]

You could also look fror cranking rpms on a scanner, if none this would point you to the cps or wiring to the module from the cps or the icm itself.

[433red]

Originally Posted by maxwedge

You could also look fror cranking rpms on a scanner, if none this would point you to the cps or wiring to the module from the cps or the icm itself.

Excellent idea! Efficient yet simple. Thanks for the suggestion.