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crank trigger or coil module bad?

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Blazer406

Mechanical Engineer
Joined
May 2, 2002
Messages
5,068
Ok guys,

I bought my theft recovery '87 GN a few months ago from the original owner. It had been sitting since Nov. 01.... I have driven it periodically in the past month or so... replacing a few things..... drained fuel... replaced fuel pump....filter... plugs.... wires.... got a DirectScan....... reset IAC per "how-to" on gnttype.org..... set TPS.... all has seemed to do well.... On some of my "test runs....... (I mean flogs)...... It seems to pull good through first.... and sometime... (not all the time) close to the top of second.... or third... or both..... it is like someone hit the kill switch for like 1/2 of a second...... ( the check engine light would light up simultaneously... and go back out)... and after like 1/2 second... it would pick right back up where it left off..... I have logged this on DS..... it looks like someone unhooked the battery for a split second....... data looks good... an .05 seconds later...... coolant temp goes to like -37..... TPS goes to 0....... IAT... goes to - xx deg.... ect..... then like .2 seconds later.... they come back up........

I have always suspected the orange wire coming off the battery to the ECM had a bad weatherpack connector...... but never have proved it......

Last night.... it exibited the same problems..... except it died all together.... and would not re-crank...... had to get pulled home. I checked all the fuses... looked good.... (I was not logging at the time it quit). I hooked up DS when I got home..... DS showed some injector pulse width while cranking.... (so I think the cam sensor is ok....)

After the battery charged all night.... I tried to crank it this morning.... wouldn't hit a lick......

Any ideas?

I am leaning toward the coil module under the coil pack.......

What are your thoughts....?

If that is the consensus..... where is a good place to get a reasonably priced replacement..... (perferrably local... i.e. O'rileys...Autozone or something.....)

FWIW.... car has 139k miles on it.
 
After trying to crank it some with DS monitoring real time..... I noticed this:

It never registers any RPM while cranking.... I would think... if the ECM is getting pulses from the crank sensor... it would register some rpm.... not 0 ... but I am unsure.
I unbolted the coil pack from the module..... and the green stuff in there is gooey..... which indicates that the module has gotten real hot.... I will probably replace that tomorrow and see if that was it.... since it needs replacing anyway.
 
Beware of Autozone's "Wells" ignition products. I have seen several bad coils new in the box. Or they'll run good until they get hot and then they crap. I would buy only GM brand modules/coils. I have already wasted my money, don't waste yours.
 
You can use a sensor testor such as an "Actron" to test the crank sensor. I bought it at Sears.
 
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