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Old 11-26-2005, 01:59 AM   #1
dodger65
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93 cutlass supreme-no spark

here's one for y'all

1993 cutlass supreme 3.4 dohc v6

rebuilt motor, used to run (post rebuild), albeit poorly...

now does not run, has no spark... here's the weirdness (to me at least)

crank pos sensor checked-ok
module is known good module
2 sets of good coils tried
new wires and plugs

originally, i found 2 bad coilpacks and the wires were twitchy (either open or good resistance until you moved them a little) replaced them. still no spark...

i can take the coilpacks off and jumper a noid light to the terminals and they all seem to be firing at the right intervals when cranking, but put the coilpacks and wires on ...... no spark

anyone run across one of these weird ones before? i figure it's probably something simple that i don't see b/c i've been in it too long...
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Old 11-26-2005, 02:13 AM   #2
67Coronet383
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Start simple.
What is the voltage at the coil on start and run, and what is the OHM reading from battery ground to coil ground terminal.
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Old 11-26-2005, 04:30 AM   #3
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Lift up the coils and module. Make sure the contact surfaces between the mod and the bracket are clean. If they're not, you lose ground to the module and you'll have the same symptoms. I had this kick my ass once thanks to somebody "helping" me. A loose bracket will also cause the same problem.
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Old 11-26-2005, 07:03 AM   #4
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Yes check all chassis connections for tightness and corrosion.

I too got tested by a similar problem. Ended up being knackered valve stem seals and the oil vapour was snuffing the spark.
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Old 11-26-2005, 04:27 PM   #5
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Quote:
Originally Posted by vwhobo
Lift up the coils and module. Make sure the contact surfaces between the mod and the bracket are clean. If they're not, you lose ground to the module and you'll have the same symptoms. I had this kick my ass once thanks to somebody "helping" me. A loose bracket will also cause the same problem.

that's all clean, and the last thing i did to it before i came in last night was run a jumper wire from the negative battery terminal to the bracket and module... still nothing...
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Old 11-26-2005, 05:43 PM   #6
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how was the crank sensor tested? just an ohms test is probably the least effective, KOEC ac waveform and signature test would show you exactly what the signal to the computer looks like.
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Old 11-26-2005, 06:20 PM   #7
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Quote:
Originally Posted by BanffAutoSpa_ap
how was the crank sensor tested? just an ohms test is probably the least effective, KOEC ac waveform and signature test would show you exactly what the signal to the computer looks like.

the original sensor and the new sensor were tested on the little tester thingy that autozone has... and if i connect it to a meter when cranking, it definitely generates an AC voltage.... it seems (to me) to be somewhere between the module and the plugs, b/c

"i can take the coilpacks off and jumper a noid light to the terminals and they all seem to be firing at the right intervals when cranking, but put the coilpacks and wires on ...... no spark"

but is the jumper maybe an insufficient ground? i don't think it needs to carry any real amperage to the module, does it?
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Old 11-27-2005, 04:24 PM   #8
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bumpity bump
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Old 12-03-2005, 03:31 AM   #9
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Quote:
Originally Posted by dodger65
bumpity bump
Updates?
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Old 12-03-2005, 06:41 PM   #10
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Quote:
Originally Posted by vwhobo
Updates?

well, i haven't been able to do much this week b/c i've been on call at work (i now know better than to start doing something when i'm on call )

what i did last week was re-mount the coilpacks and bracket to the motor, and run a completely seperate power source to the coil. at this point, i'm getting sporadic spark to all the cylinders, but i'm wondering if the plugs are fouled. i've heard people talk about fuel fouled spark plugs before, but it doesn't seem to make a whole lot of sense---your opinion?

also (you're gonna verbally bitch slap me for this), my current spark detection method is an inductive timing light (i find that it works ok, generally, for detecting spark. i'm sure there's better ways, but unless it's really cheap, i can't really justify buying something higher tech for a hobby...)

i'm just looking for a different POV on this. i've had a couple of vehicles that were reluctant to start b/c the motors were somewhat high mileage and they had been sitting so long, the rings weren't sealing well enough to start the motor (tranny fluid fixed that), but A) i don't think that would affect the spark, B) this is a reasonably fresh motor, and C) everything in the ignition system is new at this point. not that i was replacing things just guessing--everything i replaced was bad...

so that's what's going on... plus the bendix is taking a dump in the starter, so today, it started zinging after a couple of revolutions...
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Old 12-04-2005, 11:34 PM   #11
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Quote:
Originally Posted by vwhobo
Updates?

there's your updates... any ideas?
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Old 12-04-2005, 11:41 PM   #12
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Quote:
Originally Posted by dodger65
there's your updates... any ideas?
Well it seems as though you've covered all the bases. Other than installing a new starter, it might be time to slave in a different computer and see what happens. You know, the old replace with a known good unit deal.
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Old 12-04-2005, 11:43 PM   #13
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Quote:
Originally Posted by vwhobo
Well it seems as though you've covered all the bases. Other than installing a new starter, it might be time to slave in a different computer and see what happens. You know, the old replace with a known good unit deal.

that's kinda what i was thinking, but aren't gm dis almost a stand-alone system w/ no computer input until about 400 rpm or so? what's your opinion on the "fuel fouling" thing?
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Old 12-04-2005, 11:49 PM   #14
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Quote:
Originally Posted by dodger65
that's kinda what i was thinking, but aren't gm dis almost a stand-alone system w/ no computer input until about 400 rpm or so? what's your opinion on the "fuel fouling" thing?
Theoretically yes, but... I've had my ass kicked by using that train of thought and then finding out that it's not 100% accurate. Besides, if you can put your hands on one it only takes five minutes to find out. The spark plugs could definately be a factor. Once again, it would only take a second to swap in a known good plug when doing a spark test to see.
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Old 12-04-2005, 11:59 PM   #15
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Quote:
Originally Posted by vwhobo
Theoretically yes, but... I've had my ass kicked by using that train of thought and then finding out that it's not 100% accurate. Besides, if you can put your hands on one it only takes five minutes to find out. The spark plugs could definately be a factor. Once again, it would only take a second to swap in a known good plug when doing a spark test to see.

ok, i'll give that a shot, thanks...
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