Twice now I have gone to AutoZone with ignition modules (aka ESC, IDI, etc), both of which passed all tests on the Wells Analyzer but neither of which would run in the car. Evidently something critical is not being tested or loaded enough.

Symptoms were either does not start at all or started, ran briefly, then quit never to run again. Fuel was present and pressure was good. Crank sensor showed AC on crank. Everything pointed to module but tester insisted was good. Replacement of module cleared problem.

Spare ignition module and coil set is really a good thing to have & swap is easy. Then you know.

Thanks, Padgett. I've often wondered about the accuracy of that tester. It seems too good to be true. I don't think it'* really possible to design a 'one unit tests all' analyzer like that.

I guess the best course of action would be to swap a spare, rather than get a suspected ICM tested. Damn good thing there'* alot of 3800'* out there. Easy to find a unit to 'borrow'.

Been in contact with Wells, has the same parent company as Champion Labs of oil filter fame. Since I still have two modules that tested good but did not run they asked me to send them in for testing. We shall see what happens.

I do consider this important since the electronics involved are difficult for anyone to troubleshoot as the Crank sensor, Electronic Spark Control, Engine Control Module, Injectors, and assorted harnesses are all involved. Even following the six page "cranks but does not run" troubleshooting procedure in the manual often leads to conflicting results and confusing results. (when I tapped the harness pin that is supposed to rattle the injectors, the cooling fan came on...)

This is why one of my later tests is something that is not very safe - inject about a 1/2 oz of gasoline into the manifold & crank. If >nothing< happens you have no fire which means either crank sensor or ESC and not injectors or ECM.

Do not know about anyone else but it is difficult for me to lay U$145 on the counter for a non-returnable part when the super lotsa lights Wells tester says the original is good but when everything else has been eliminated...

That said I converted my '88 "C" to the later Delco ignition and it seems to run very well/is smoother than with the Magnavox but it took two "recycled" sets to come up with a good one so as soon as I have another good one will problably convert the '90 also.

Thanks, Padgett, for the heads up on the Autozone tester. I can't help but wonder how accurate all of their other tests are. :?