greetings all,

....1988 coup...90k milkes...terrific shape ....in the past 3 years i have gone through 8 ignition modules in my distributor (another yesterday) and cannot figure out as to why this is happening....coil is new, rotor, cap, wires, etc all new.....

...this is NOT an issue as to if the ignition module was installed correctly or using enough heat sink compound because i did and have been all along.....

.....could the capacitor under the distributor cap be taking the module out somehow?...i have not replaced that and cannot see arbitrarily being advised to replace that w/o reason... ....

....i had been using after-market stuff and all of these went...when i got the car, i took out the orig ac delco/gm module that was in it and replaced it while chasing down another problem....

....i put it back in yesterday and car starts up as in all the other replacements i have done...hell, there are guys on here that have never replaced nor needed to replace theirs in years and thousands of miles!...

...any informed suggestions would be appreciated!

 

A lot of those "made in foreign place" modules are real junk. I have gone through a few on another car of mine. The connector welds to the internal circuit boards are poorly made and the vibration damping is nonexistent in most of them. So, not surprising they crap out pretty quick. A capacitor was used to prevent the coil back emf spikes from arcing across points in the old "points & condensor" distributors, and I suppose would also protect an electronic module from the same. If it's bad, it could be letting spikes take out the electronics in the modules.

 

...thanks for the reply..i was aware that some of the after market stuff is crapola but, have had some very good luck with some but, not all.....was also aware of the capacitor use in the "earlier" points car and have been considering that as a cause for a while now....would you happen to have a parts number for that or know if it is a dealer item?....thanks again for the reply....

 

Sorry, don't have a part number. NAPA always has pretty good stuff when I need it, and they don't seem to have as much junk as the other places do.

 

A couple things. First, have all 8 been the same brand? and have you had them test the failed ones? Autozone will check them for free. I have a hard time with the fact you've replaced 8 in such a short period of time, as far as I know my 87 with 110K on it has only had one replacement. I did purchase it from Autozone, although I really like NAPA parts.

 

...thanks for the reply...NO, they were two different brands (i can look in my book and get you the brands if need be)....i did some research and found the capacitor assembly (capacitor NOT sold separately) for under my distributor yesterday in case anyone is interested (DELCO PART # 1892260)...dealer lists for $35+ and auto zone has duralast for approx. $11.00 ....i just may take my old one to "az" and have them test it anyway...i remember in the older "points" car, if the cap shorted out you'd get no spark so, could be the issue here....

 

Very well could be causing a problem, it used to be standard when replacing points to replace the capacitor. But I doubt a capacitor would take out an ignition module! Have you tested your pickup coil and connections to it?

 

..p-u coil has been replaced already...i still would think that the cap serves generally the same purpose as the "old cap days" and if it took a dump, would either short "spark" to ground (giving a "no-start" status or, allow spikes back into the ignition module and over time may cause it to fail....valid argument?

 

The capacitor in HEI ignition systems is to keep voltage spikes from getting into any other electronics in the car. You will still have the same spark if you remove the capacitor. Do you know the difference between dielectric grease and heat sink grease? Heat sink grease is supposed to be put between the spark module and its mounting place. Heat sink grease is white, and dielectric grease looks like vaseline. Don't use dielectric grease in place of heat sink grease. One thing that can shorten the life of the spark module is to use an aftermarket spark coil and particularly ones that claim higher voltage. The spark control module is designed for a particular spark coil!

 

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...thanks for the reply....

"Do you know the difference between dielectric grease and heat sink grease? "..YES!, ABSOLUTELY!

"Heat sink grease is supposed to be put between the spark module and its mounting place.". .YES, I AM AWARE OF THAT FULLY!

"Heat sink grease is white, and dielectric grease looks like vaseline." ..YES, I AM AWARE OF THAT FULLY!

"Don't use dielectric grease in place of heat sink grease." ...NEVER DID AND NEVER WILL!

"One thing that can shorten the life of the spark module is to use an aftermarket spark coil and particularly ones that claim higher voltage. The spark control module is designed for a particular spark."
I AM USING A STOCK COIL AND ALWAYS HAVE.

 

I drive my 87 Corvette every day, it has 223,000 miles and the spark module has been replaced once, with a GM part. Hint.

 

I WOULD LOOK ANOTHER PLACE AS WELL.
You might try hooking up an analog volt meter and watching it as you drive. If your alternator is spiking your electrical system, it might be that the modules you speak of could be the most sensitive to electrical spikes.
Monitor your electrical voltage after:
1. first starting up
2. after a long idle such as a long traffic light
3. high speed blast
4. cruising speed
5. after turning on or off high current items such as the A/C. Or, A/C on, brakes on, cooling fan kicking on, headlights on, radio blaring.
6. If you have a speaker amp, it could be spiking your system as well
Another thing might be a sticky belt tensioner.
don't limit yourself to the failed unit as your subject of focus

 

....well, good for you!...wish i could say the same..however, the original ignition module that was once in the car and of which i put back in, took a dump about a week ago and it was gm NOT aftermarket!.....the current replacement is a gm module so, i'll see how long that lasts......will change out the capacitor assembly tomorrow and set a baseline to see how long this one will last!

 

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WOULD LOOK ANOTHER PLACE AS WELL.
You might try hooking up an analog volt meter and watching it as you drive. If your alternator is spiking your electrical system, it might be that the modules you speak of could be the most sensitive to electrical spikes.**8 modules later and 1 original?...i can see the aftermarket stuff but, the gm stuff too?...the only thing left is the capacitor assembly which i will replace tomorrow...

Monitor your electrical voltage after:
1. first starting up **voltage will rise as the alt spins up to speed to recharge the battery and then will level off when no charge is needed. the alternator will "turn on" when the power requirements of the car require it to such as fans, a/c, headlights, etc.

2. after a long idle such as a long traffic light **see #1, i have no fluxuations in voltage that are noticeable and "spikes" would be so small and so fast that they would be undetectable for the most part.

3. high speed blast **can't see the relevancy in this

4. cruising speed **can't see the relevancy in this

5. after turning on or off high current items such as the A/C. Or, A/C on, brakes on, cooling fan kicking on, headlights on, radio blaring. **see #1

6. If you have a speaker amp, it could be spiking your system as well **nope, all stock and no amps, etc

Another thing might be a sticky belt tensioner.**nope, replaced the bearing about a year ago and inspected spring and all is well. don't see the relevance in this.

don't limit yourself to the failed unit as your subject of focus **believe me, i am not!..i carry a spare module with me at all times.

 

Mailman, I'm trying to help, I am not talking down to you. Do you have normal voltage when driving? (13 to 14.7 volts) Very high alternator voltage can shorten spark module life, like 16 volts or higher. Heat is a real enemy of solid state circuits. Do you see anything in the spark module mounting that either won't allow heat to transfer from the module to the mounting? Mount surface needs to be flat and in intimate contact with the module. Do you have unusually high engine temps, even only for short times? Is the spark coil also GM? An open circuit on the output of the spark coil will cause higher than normal voltage spikes on the primary which stresses the switching transistor in the spark module and shortens its life. Do you have a miss, rough idle? If so, you might check the resistance of each spark plug wire, they should be close to 5000 ohms per foot.

 

...whoa!..i never thought that you were "talking down" for a minute!...

Do you have normal voltage when driving?(13 to 14.7 volts) YES Very high alternator voltage can shorten spark module life, like 16 volts or higher. AM AWARE OF THAT Heat is a real enemy of solid state circuits. Do you see anything in the spark module mounting that either won't allow heat to transfer from the module to the mounting? THAT WAS ONE OF THE FIRST THINGS I CHECKED BEFORE MOUNTING TO A CLEAN SURFACE AFTER REMOVING THE OLD COMPOUND WHICH SOME DO NOT DO Mount surface needs to be flat and in intimate contact with the module. IT IS Do you have unusually high engine temps, even only for short times? NO, NEVER GETS OVER 205* Is the spark coil also GM? YES An open circuit on the output of the spark coil will cause higher than normal voltage spikes on the primary which stresses the switching transistor in the spark module and shortens its life. Do you have a miss, rough idle? NO MISS, NO ROUGH IDLE BUT, GETTING READY FOR PLUGS SHORTLY!If so, you might check the resistance of each spark plug wire, they should be close to 5000 ohms per foot.[/QUOTE] WIRES ALMOST NEW BUT, NOT CHECKED YET..

 

Another thought occurs to me. The two primary wires on the spark coil should not be interchanged. You will still get a normal spark if interchanged, but the spark module will get larger voltage spikes which shortens the life of the module. I'll see if I can find out which color wire goes where and you can check if yours is wired correctly.

 

....i appreciate that.....just a side note; today, i brought down the ignition module that was the original in the car when i bought it and that went bad about a week ago...to my surprise and after 3 tests on the machine at auto zone, IT TESTED GOOD! .....now, i am looking a bit harder at the capacitor assembly!

 

A couple items: It's been my experience that jfb has a good working knowledge of electronic items. You can trust his comments and suggestions.
I'm unclear (without a schematic) where the capacitor in question is hooked up. Unlike points systems, quality electronic sistems do not need, and rarely use, a capacitor on the C- portion of the circuit. I assume the cap in question is on the battery (B+) side of the module. Unless there are wild supply spikes on B+ (measurable only with an oscilloscope) that the cap is not filtering, the cap should have no effect on the module operation. If there is a loose connection on the alternator/battery line, the alternator may produce high voltage spikes (around 60 to 100 volts) due to current/inductance issues. This could overheat the module from continually trying to clamp the voltage spikes.
A coil short/dielectric issue may allow the coil secondary voltage to arc over to the primary winding (and the module output transistor). This will put a little more stress on the module.
JFB is correct about the coil polarity issue. It takes a higher plug voltage to arc over if the center electrode polarity is reversed (to positive).
Do you know if the ignition coil has OEM specs? A low inductance coil will cause the module to heat up as the output transistor has to deal with higher average current levels (due to the faster current rise time and the current limiting feature built into some modules).
Just some thoughts. Good luck with your debugging!

 

I'm unclear (without a schematic) where the capacitor in question is hooked up.
***it is an assembly and i think i have posted a part number..one side of the ignition module plugs directly into it if i am not mistaken...
Unlike points systems, quality electronic sistems do not need, and rarely use, a capacitor on the C- portion of the circuit.***see above.

I assume the cap in question is on the battery (B+) side of the module.
**unknown as i have not had a chance to hit the helms yet..however,i do have the replacement in front of me..Unless

there are wild supply spikes on B+ (measurable only with an oscilloscope) that the cap is not filtering, the cap should have no effect on the module operation.
***well, as far as i can tell, there exists the possibility of something trashing either the power to the module or the spark enanating from it and since i see no anomalies in the wiring at this time, no shorts or breaks, i have to assume that that could be the culprit, not HAS to be the culprit...

If there is a loose connection on the alternator/battery line,
***none...
the alternator may produce high voltage spikes (around 60 to 100 volts) due to current/inductance issues. This could overheat the module from continually trying to clamp the voltage spikes.
A coil short/dielectric issue may allow the coil secondary voltage to arc over to the primary winding (and the module output transistor). This will put a little more stress on the module.

JFB is correct about the coil polarity issue. It takes a higher plug voltage to arc over if the center electrode polarity is reversed (to positive).
*** he said that he was going to verify that for me later. however, i put everything on the way it came off. however, that is not to say that it wasn't f__ked up that way when i got the car.

Do you know if the ignition coil has OEM specs?
came from the dealer so, i would surmise so..

A low inductance coil will cause the module to heat up as the output transistor has to deal with higher average current levels (due to the faster current rise time and the current limiting feature built into some modules).
Just some thoughts. Good luck with your debugging!
***i will figure this out or at least carry a suitcase full of modules in my car in the mean time!