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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: square81 on June 23, 2019, 02:42:42 pm

Title: Possible hei distributor issue
Post by: square81 on June 23, 2019, 02:42:42 pm
Hey guys whats happening. Ive got a problem that had to come at the wrong time. Was going to head away on a camping trip truck just quit like you shut the key off. 1981 chevy 350 auto. Coasted into kfc. Took a quick peek under hood and fuse panel. All looked ok. Then tried starting away it went. Got a few mins down the road quit again. Sat for a few mins started again. It quit on me 5 more time before i got home. Left it and took a buddies truck instead.
I replaced the distributor 2 years ago with a complete acell unit. The old distributor gave up after 36 years of service. Found a break in the pic up coil.
When this happens it has power at distributor but no spark. Let it sit for a few mins has spark and fires right up.
Tried a known good coil still had issue, left tach unhooked, while it was running 13-14 volts at the battery.  These were just quick checks before leaving. Im maybe missing things to check.
Thinking maybe the ignition module is having issue. Not a common issue.
Whats your guys thoughts. Never had issues with hei's before always reliable. 
Thinks in advance.

Title: Re: Possible hei distributor issue
Post by: bd on June 23, 2019, 04:57:54 pm
Be glad it happened before you were in the outback.  Probably the ICM, but could be the pickup coil.  Can you detect a tach signal while cranking with no start?
Title: Re: Possible hei distributor issue
Post by: SilverMiner on June 23, 2019, 07:07:14 pm
I recently had similar issues with my 1980. The permanent fix was replacing the entire distributor for peace of mind sake, but a short term fix was replacing the control module as you suspected. After comparing the individual parts cost (control module, pickup ring, etc. etc.) it made sense to me to spend the additional $40 or so for a complete unit.
Title: Re: Possible hei distributor issue
Post by: square81 on June 23, 2019, 07:17:59 pm
I was lucky forsure. I cant remember looking at the tach while starting. But the tach does work when plugged in. I did replace the while distributor a couple years ago for peace of mind as well. All mine needed was the pick up coil. It was half the price of a new unit and i still had to take it out. Thanks for the responses so far. I'm going to try a ignition module tomorrow and will report back. Thanks
Title: Re: Possible hei distributor issue
Post by: square81 on June 25, 2019, 10:16:28 pm
So I changed out the ignition module tonight. It had that bad burnt electrical smell as soon as i opened the distributor. They sure skimped out on the heat sink grease. Its less then 2 years old, not really happy about that failing so soon .
 Put the new module on and truck fired right up. Haven't drove it yet to see if its 100% fixed but hopefully this week.
Title: Re: Possible hei distributor issue
Post by: bd on June 25, 2019, 10:30:59 pm
How did the inside of the cap look, especially in the vicinity of the carbon button?
Title: Re: Possible hei distributor issue
Post by: square81 on June 26, 2019, 11:59:48 am
I didnt look real close to it. No melting damage. But it had that strong electrical burning smell. Maybe pop it back off tonight and look real close. Would i see damage to the carbon button and surrounding area?
Title: Re: Possible hei distributor issue
Post by: bd on June 26, 2019, 01:29:01 pm
My question was triggered by your comment regarding a strong "burnt electrical" odor.  The idea is to recognize any visually obvious external cause for ICM failure so as to avoid a repeat.
Title: Re: Possible hei distributor issue
Post by: square81 on June 26, 2019, 05:35:51 pm
Ok wow! I'll be checking tonight forsure. Thats very burnt up. The module failing cause this or another issue? Thanks for showing me that.
Title: Re: Possible hei distributor issue
Post by: bd on June 26, 2019, 07:01:45 pm
My comment was inadvertently misleading.  The ICM failure may not be connected to any external cause, meaning that the ICM may have simply failed.  Again, the question was based on the electrical odor you detected.

FYI - The cap damage in that particular image was probably a result of excessive carbon button erosion and/or unwanted button-to-rotor contact air gap that gradually escalated into spark scatter, localized overheating of the cap insulation in the vicinity of the button and subsequent dielectric breakdown and perforation.  If the cap exhibits that kind of extensive arc damage then you are faced with replacing the distributor cap and the ignition coil.  But, until you look, it is moot.
Title: Re: Possible hei distributor issue
Post by: JohnnyPopper on June 26, 2019, 07:58:08 pm
Sufferin Spark Scatter! That's one hot cap!