| [GMCnet] Suggestion, ground your distributor today! [message #294345] |
Sun, 24 January 2016 22:05  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Today I finally solved a two year electrical gremlin. Since installing the new S&J engine in the Clasco I have experienced a random backfire/misfire/hesitation. It occurred for no apparent reason and then went away sometimes for a thousand miles. I replaced everything I could think of - distributors, modules, coils, carb to EFI , fuel pumps, fuel filters, fuel venting, etc.
What I found today was what appears to have been a randomly high resistance ground where the distributor is held to the engine block by the rocker and bolt that holds the distributor in the correct timing rotation. When the resistance build up to the point the voltage drops below the threshold required for proper function, the Gmc misfires, hesitates and mimics all the symptoms of a bad module or coil. Those backfires might well take out an otherwise good coil or module causing a seemly unending random failure mode.
What I did to finally end this cycle was to drill and tap a hole in the aluminum distr body to mount a wire ground directly to the block. But, in addition, I had to replace the brand new coil in a brand new custom built distributor with an advance curve matched to the FiTech EFI.
Once that was done we have had no recurrence - yet! I will post if we do, but this scenario fits all the many symptoms and I think is a root cause solution. I suggest you do the same today whether you have experienced these symptoms or not.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] Suggestion, ground your distributor today! [message #294347 is a reply to message #294345] |
Sun, 24 January 2016 22:29  |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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Dick Paterson specifies to run a ground wire for his distributors for that
very reason.
Sully
77 royale
Seattle
On Sunday, January 24, 2016, Gerald Work wrote:
> Today I finally solved a two year electrical gremlin. Since installing
> the new S&J engine in the Clasco I have experienced a random
> backfire/misfire/hesitation. It occurred for no apparent reason and then
> went away sometimes for a thousand miles. I replaced everything I could
> think of - distributors, modules, coils, carb to EFI , fuel pumps, fuel
> filters, fuel venting, etc.
>
> What I found today was what appears to have been a randomly high
> resistance ground where the distributor is held to the engine block by the
> rocker and bolt that holds the distributor in the correct timing rotation.
> When the resistance build up to the point the voltage drops below the
> threshold required for proper function, the Gmc misfires, hesitates and
> mimics all the symptoms of a bad module or coil. Those backfires might
> well take out an otherwise good coil or module causing a seemly unending
> random failure mode.
>
> What I did to finally end this cycle was to drill and tap a hole in the
> aluminum distr body to mount a wire ground directly to the block. But, in
> addition, I had to replace the brand new coil in a brand new custom built
> distributor with an advance curve matched to the FiTech EFI.
>
> Once that was done we have had no recurrence - yet! I will post if we do,
> but this scenario fits all the many symptoms and I think is a root cause
> solution. I suggest you do the same today whether you have experienced
> these symptoms or not.
>
> Jerry
>
> Jerry Work
> The Dovetail Joint
> Fine furniture designed & hand crafted
> in the 1907 former Masonic Temple building
> in historic Kerby, OR
> http://jerrywork.com
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Suggestion, ground your distributor today! [message #294351 is a reply to message #294347] |
Mon, 25 January 2016 00:51 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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sgltrac wrote on Sun, 24 January 2016 22:29Dick Paterson specifies to run a ground wire for his distributors for that
very reason.
Sully
77 royale
Seattle
And Dick puts a stud with a ring terminal on every one he builds so all you have to do is add the wire to the block when you install it.
I glad you found the problem.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Suggestion, ground your distributor today! [message #294380 is a reply to message #294345] |
Mon, 25 January 2016 12:28 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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This actully is an important issue for those of you that have rebuilt engines.
The block gets painted. And the distributor hole (socket )also gets a coating of paint. (Insulator to ground) Sometimes the clamp gets painted too. The oil makes a poor conductor for the rest if the unit down in the engine and you get the problem Jerry is saying.
I soldered a ground wire (teed) into the ground wire that comes out of the distributor to the coil connector and connected it to the block through a spade connector for easy removal. That wire is grounded in the distributor on the module pad.
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] Suggestion, ground your distributor today! [message #294402 is a reply to message #294380] |
Mon, 25 January 2016 16:07 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The other thing that happens over the years is you get bi-metal corrosion at that joint. The block and intake are steel while the distributor is aluminum. I had one on a 403 that was corroded so bad that we could not get the distributor to move at all to adjust the timing. It looked like I was going to have to use a dent slide hammer type puller to get it out and we would probably destroy the distributor in the process. It turned out that the timing was close to being correct that we just left it alone. The guy sold the coach 2 years later. So now the problem belongs to someone else.
I also saw one where the guy had a gasket down there. He was not having a problem and wanted to keep the gasket. So we installed a ground wire from to the base of the distributor to the engine to insure a good electrical connection.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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