Home » Public Forums » GMCnet » Another mystery ignition module failure
| Another mystery ignition module failure [message #334169] |
Fri, 29 June 2018 08:11  |
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SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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Senior Member |
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To date I've had 3 ignition modules fail in the driveway. Parked, batteries disconnected. Go to restart and nothing, replace module, fires on first crank.
I have my distributor grounded independently from the lockdown, and running GM / AC Delco branded modules. I have my 12V source on a relay that doesn't close until key is turned. Mystery.
Anyone else experience this?
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
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| Re: [GMCnet] Another mystery ignition module failure [message #334171 is a reply to message #334169] |
Fri, 29 June 2018 08:23  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Sean,
That sounds suspiciously like a bad connection somewhere near the
distributor or module. PERHAPS when you replace the module, you abrade the
bad connection so that it operates again -- until it's set undisturbed for
a while so that it can re-corrode. Have you tried "jiggling" everything
nearby before replacing the module? Tried re-inserting one of the "failed"
modules?
Ken H.
On Fri, Jun 29, 2018 at 9:15 AM Sean Kidd via Gmclist <
gmclist@list.gmcnet.org> wrote:
> To date I've had 3 ignition modules fail in the driveway. Parked,
> batteries disconnected. Go to restart and nothing, replace module, fires on
> first
> crank.
>
> I have my distributor grounded independently from the lockdown, and
> running GM / AC Delco branded modules. I have my 12V source on a relay that
> doesn't close until key is turned. Mystery.
>
> Anyone else experience this?
> --
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Another mystery ignition module failure [message #334172 is a reply to message #334169] |
Fri, 29 June 2018 08:51 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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What are you putting under the modules when you install them? Unless you put the proper heat conductive grease under it they will quickly fail. Don’t just use dielectric grease which many auto parts stores will tell you it what to use (including an ignorant clerk at a local NAPA store).
New ones should come with a small capsule of the proper material. But if you buy a used one at at swap meet or get one at a junkyard buy the right grease.
Emery Stora
77 Kingsley
Frederick, CO
> On Jun 29, 2018, at 7:11 AM, Sean Kidd via Gmclist wrote:
>
> To date I've had 3 ignition modules fail in the driveway. Parked, batteries disconnected. Go to restart and nothing, replace module, fires on first
> crank.
>
> I have my distributor grounded independently from the lockdown, and running GM / AC Delco branded modules. I have my 12V source on a relay that
> doesn't close until key is turned. Mystery.
>
> Anyone else experience this?
> --
> Sean and Stephanie
> 73 Ex-CanyonLands 26' #317 "Oliver"
> Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
>
> Colonial Travelers
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: Another mystery ignition module failure [message #334173 is a reply to message #334169] |
Fri, 29 June 2018 09:04 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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SeanKidd wrote on Fri, 29 June 2018 09:11To date I've had 3 ignition modules fail in the driveway. Parked, batteries disconnected. Go to restart and nothing, replace module, fires on first crank.
I have my distributor grounded independently from the lockdown, and running GM / AC Delco branded modules. I have my 12V source on a relay that doesn't close until key is turned. Mystery.
Anyone else experience this?
Sean,
I agree with KenH. (This is a very common thing.)
I have a similar problem. It was just one of my many times fighting with HEI that I remember well.
There are two immediate issues with the HEI module that cause grief both can be inadvertently cleared by a removal and reinstallation.
The obvious one is that the push on connectors loose tension. They can feel like they are good, but when installed, are actually loose. This can be corrected by giving them just a little squeeze with a pair of pliers. Don't squeeze them too much or they break when you try to put them back on.
The less obvious one is that the module ground is made by a clean metal pad on the bottom of the module. This one gets to be a problem because the center of the module has to have a load of heat sink paste that happens to also be an electric insulator. When installing, be sure that the ground tab is clear.
Good Luck
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Another mystery ignition module failure [message #334174 is a reply to message #334169] |
Fri, 29 June 2018 09:05 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The main things that takeout modules.
1. Non-Delco module have a higher failure rate. Use an AC Delco module
2. Total Gap too high in the spark path. Meaning:
2a. The plugs are gapped too wide. Set the gap to .040"
2b. Gap too wide between rotor and cap contacts. Look closely at condition of rotor and cap contacts. Check for excess distributor shaft play side to side and up and down.
2c. Make sure spring loaded cap center contact is not worn out or missing. I had one missing one time and the HEI distributor still ran.
2d. Open spark plug wire(s) - Check with ohm meter
2e. High resistance or open plug - Check with ohm meter
2f. Re-check for good ground between distributor frame and the engine block (not the battery). This is the return path for all high voltage going to the plugs.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Another mystery ignition module failure [message #334177 is a reply to message #334172] |
Fri, 29 June 2018 08:58 |
Ethan James
Messages: 32
Registered: October 2016
Location: Roanoke, VA
Karma: 1
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Member |
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At a rally last year one of the module died in one of the coaches. After
replacing it did it again, in the end it was a bad alternator causing the
problem.
-Ethan James
76' Glenbrook
On Fri, Jun 29, 2018 at 9:52 AM Emery Stora wrote:
> What are you putting under the modules when you install them? Unless you
> put the proper heat conductive grease under it they will quickly fail.
> Don’t just use dielectric grease which many auto parts stores will tell you
> it what to use (including an ignorant clerk at a local NAPA store).
>
> New ones should come with a small capsule of the proper material. But if
> you buy a used one at at swap meet or get one at a junkyard buy the right
> grease.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>> On Jun 29, 2018, at 7:11 AM, Sean Kidd via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> To date I've had 3 ignition modules fail in the driveway. Parked,
> batteries disconnected. Go to restart and nothing, replace module, fires on
> first
>> crank.
>>
>> I have my distributor grounded independently from the lockdown, and
> running GM / AC Delco branded modules. I have my 12V source on a relay that
>> doesn't close until key is turned. Mystery.
>>
>> Anyone else experience this?
>> --
>> Sean and Stephanie
>> 73 Ex-CanyonLands 26' #317 "Oliver"
>> Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1
> LSD Honda 6500 inverter gen.
>>
>> Colonial Travelers
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Another mystery ignition module failure [message #334183 is a reply to message #334174] |
Fri, 29 June 2018 09:59 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Try tapping your spark plugs at .040". The factory originally wanted gaps
at twice that much, and had lots of module and coil failures. Their fix,
closing down the gaps. Also, heat sink compounds are VERY CRITICAL. Use
plenty under the module. Make sure of your grounds. Use good secondary
conductors, and a trick I use, silicone grease( non conductive type) on the
boots to facilitate removal. I personally have had far more failures with
MSD ignition stuff than I have with Genuine GM HEI. High humidity areas of
the country will experience more ignition troubles. Just a fact of life.
Jim Hupy
Salem, Or
On Fri, Jun 29, 2018, 7:06 AM Ken Burton wrote:
> The main things that takeout modules.
>
> 1. Non-Delco module have a higher failure rate. Use an AC Delco module
>
> 2. Total Gap too high in the spark path. Meaning:
>
> 2a. The plugs are gapped too wide. Set the gap to .040"
>
> 2b. Gap too wide between rotor and cap contacts. Look closely at
> condition of rotor and cap contacts. Check for excess distributor shaft
> play side
> to side and up and down.
>
> 2c. Make sure spring loaded cap center contact is not worn out or missing.
> I had one missing one time and the HEI distributor still ran.
> 2d. Open spark plug wire(s) - Check with ohm meter
>
> 2e. High resistance or open plug - Check with ohm meter
>
> 2f. Re-check for good ground between distributor frame and the engine
> block (not the battery). This is the return path for all high voltage
> going to
> the plugs.
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Another mystery ignition module failure [message #334184 is a reply to message #334177] |
Fri, 29 June 2018 10:05 |
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Brian K
Messages: 75
Registered: May 2017
Location: Sherman Oaks, CA
Karma: 0
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Member |
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I second Ethan's comment. Although my experience also showed bad wiring caused the problem.
Last summer I took a 3000 mile round trip from Seattle to Albuquerque. Other than stupidly traveling in the middle of July (with 100+ degree heat in Utah), I lost a coil and module in Utah. When the mechanic replaced it, we found out that the Tach wire was shorting out the module and coil.
On the trip home, I lost the distributor in Wyoming. After repair and getting home, while I was having some repairs done at my friends, he said the coil died again. All along, my voltage was reading over 15 to 16. Ultimately I "encouraged" my friend to replace the alternator and this was fixed. I suspect all my problems last year with the module, coils and distributors were because (1) the 40yr old tach wire probably got hot in the desert heat, and shorted; and, more importantly, (2) my voltage regulator and alternator were bad and fried the coil and distributor.
I'm a lawyer and only play amateur mechanic on the GMC! But my logic skills tell me that I would check all those things (voltage and wiring).
Brian K
1977 Eleganza II, TZE167V100261
Sherman Oaks, CA
Rebuilt 455, New brake system, a lot of Original Equipment ready to fall apart (discovering more as I go along....)
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| Re: [GMCnet] Another mystery ignition module failure [message #334186 is a reply to message #334184] |
Fri, 29 June 2018 10:40 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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If the modules are truly bad, replace the coil.
We have seen where a coil was knocking out the modules. Once both were
replaced, they ran for a long time.
Again a Delco products seem to hold up better.
On Fri, Jun 29, 2018 at 8:05 AM, Brian Krikorian wrote:
> I second Ethan's comment. Although my experience also showed bad wiring
> caused the problem.
>
> Last summer I took a 3000 mile round trip from Seattle to Albuquerque.
> Other than stupidly traveling in the middle of July (with 100+ degree heat
> in
> Utah), I lost a coil and module in Utah. When the mechanic replaced it,
> we found out that the Tach wire was shorting out the module and coil.
>
> On the trip home, I lost the distributor in Wyoming. After repair and
> getting home, while I was having some repairs done at my friends, he said
> the
> coil died again. All along, my voltage was reading over 15 to 16.
> Ultimately I "encouraged" my friend to replace the alternator and this was
> fixed.
> I suspect all my problems last year with the module, coils and
> distributors were because (1) the 40yr old tach wire probably got hot in
> the desert
> heat, and shorted; and, more importantly, (2) my voltage regulator and
> alternator were bad and fried the coil and distributor.
>
> I'm a lawyer and only play amateur mechanic on the GMC! But my logic
> skills tell me that I would check all those things (voltage and wiring).
> --
> Brian K
> 1977 Eleganza II, TZE167V100261
> Bellevue, WA
> Rebuilt 455, New brake system, a lot of Original Equipment ready to fall
> apart (discovering more as I go along....)
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Another mystery ignition module failure [message #334190 is a reply to message #334171] |
Fri, 29 June 2018 11:19 |
rjw
Messages: 697
Registered: September 2005
Karma: 4
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Senior Member |
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Ken Henderson wrote on Fri, 29 June 2018 09:23Sean,
That sounds suspiciously like a bad connection somewhere near the
distributor or module. PERHAPS when you replace the module, you abrade the
bad connection so that it operates again -- until it's set undisturbed for
a while so that it can re-corrode. Have you tried "jiggling" everything
nearby before replacing the module? Tried re-inserting one of the "failed"
modules?
Ken H.
Sounds like the situation I had on my way out to the Reno, NV earlier this year. Numerous engine stoppages that I finally traced to the wiring harness that goes between the module and the top of the distributor cap. Every time I changed the module after the engine quit I apparently moved the connectors in the harness enough to keep it running for a while. Finally I removed the new harness I had and Installed a harness I had from my 1980's junk yard distributor and it's been running fine for the last ~3,000 miles. They don't make those harnesses the way they used to.
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
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| Re: Another mystery ignition module failure [message #334193 is a reply to message #334169] |
Fri, 29 June 2018 11:32 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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My ignition quit on me. Replacing the module got it going, only to fail soon afterward.
I replaced the whole distributor. For the cost of a coil, cap, rotor and module, you can
buy a new distributor.
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] Another mystery ignition module failure [message #334202 is a reply to message #334171] |
Fri, 29 June 2018 14:03 |
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Anonymous
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Interestingly, one of the spade connectors felt a little loose, I did squish it down a little to make a good contact, and added dielectric grease. Is there any module multimeter test procedure? I guess I can google. Thanks for your suggestion. I kept the suspected failed module to test again. by the way it’s a Springfield (Dick Patterson?)dizzy... from the coop I think. Thanks for your input.
Sent from my iPad
> On Jun 29, 2018, at 9:23 AM, Ken Henderson wrote:
>
> Sean,
>
> That sounds suspiciously like a bad connection somewhere near the distributor or module. PERHAPS when you replace the module, you abrade the bad connection so that it operates again -- until it's set undisturbed for a while so that it can re-corrode. Have you tried "jiggling" everything nearby before replacing the module? Tried re-inserting one of the "failed" modules?
>
> Ken H.
>
>> On Fri, Jun 29, 2018 at 9:15 AM Sean Kidd via Gmclist wrote:
>> To date I've had 3 ignition modules fail in the driveway. Parked, batteries disconnected. Go to restart and nothing, replace module, fires on first
>> crank.
>>
>> I have my distributor grounded independently from the lockdown, and running GM / AC Delco branded modules. I have my 12V source on a relay that
>> doesn't close until key is turned. Mystery.
>>
>> Anyone else experience this?
>> --
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Unsubscribe or Change List Options:
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| Re: Another mystery ignition module failure [message #334209 is a reply to message #334169] |
Fri, 29 June 2018 15:25 |
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SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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Senior Member |
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Thank you all, I always use Arctic Silver 5 high density Polysynthetic silver Thermal paste, I agree with Ken and others regarding the connector, as for the plugs, I will have to check, but I believe I run no more than .040.
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
[Updated on: Fri, 29 June 2018 15:27] Report message to a moderator |
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| Re: [GMCnet] Another mystery ignition module failure [message #334213 is a reply to message #334202] |
Fri, 29 June 2018 17:09 |
rjw
Messages: 697
Registered: September 2005
Karma: 4
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Senior Member |
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delbert lecky via Gmc wrote on Fri, 29 June 2018 15:03Interestingly, one of the spade connectors felt a little loose, I did squish it down a little to make a good contact, and added dielectric grease. Is there any module multimeter test procedure? I guess I can google. Thanks for your suggestion. I kept the suspected failed module to test again. by the way it's a Springfield (Dick Patterson?)dizzy... from the coop I think. Thanks for your input.
I have a ignition module tester and found that all the modules I thought were bad (actually the harness was bad) were good.
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
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| Re: [GMCnet] Another mystery ignition module failure [message #334214 is a reply to message #334213] |
Fri, 29 June 2018 18:23 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Richard,
If that's a Kent-Moore tester, don't use it on the new GM modules from
Singapore. They will check bad and no one has an answer,
except to spend more money. I can put them in a distributor, install it in
my Sun Distributor Machine and they check good. So what
is different? No one knows or cares. Welcome to modern America.
Gary Kosier
77PB w/500Cad
Newark, Ohio
--------------------------------------------------
From: "RJW"
Sent: Friday, June 29, 2018 6:09 PM
To:
Subject: Re: [GMCnet] Another mystery ignition module failure
> delbert lecky via Gmc wrote on Fri, 29 June 2018 15:03
>> Interestingly, one of the spade connectors felt a little loose, I did
>> squish it down a little to make a good contact, and added dielectric
>> grease.
>> Is there any module multimeter test procedure? I guess I can google.
>> Thanks for your suggestion. I kept the suspected failed module to test
>> again. by the way it's a Springfield (Dick Patterson?)dizzy... from the
>> coop I think. Thanks for your input.
>
> I have a ignition module tester and found that all the modules I thought
> were bad (actually the harness was bad) were good.
>
> --
> Richard
> 76 Palm Beach
> SE Michigan
> www.PalmBeachGMC.com
>
>
> Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator,
> Manny Tranny etc.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Another mystery ignition module failure [message #334235 is a reply to message #334234] |
Sat, 30 June 2018 06:37 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Ken Henderson wrote on Sat, 30 June 2018 06:27JD,
Thanks for that link! That's by far the best HEI description I've ever
seen. And it even has a reference to the GMC MH!!!
Ken H.
I also copied it and saved it on my laptop.
Good information.
Thank You.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Another mystery ignition module failure [message #334250 is a reply to message #334169] |
Sat, 30 June 2018 11:10 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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The ground lug that goes to the coil is often bad as the screw threads into plastic and only hope of connection is the star washer. Been driving GM HEI vehicles since 1975 and never had a module failure.
John Lebetski
Woodstock, IL
77 Eleganza II
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