Possible DUI distributor issues
Drifting
Joined: Jun 2025
Posts: 1,715
Likes: 597
You've asked for any thoughts.
Thus, earnestly, and without ill will or attitude; it may be time to employ a pro to put his eyes and hands on it.
? Does this car have a dedicated engine-to-chassis ground strap ? One that's fully viable ?
Thus, earnestly, and without ill will or attitude; it may be time to employ a pro to put his eyes and hands on it.
? Does this car have a dedicated engine-to-chassis ground strap ? One that's fully viable ?
Thread Starter
Racer
Joined: Aug 2017
Posts: 352
Likes: 47
From: Bham, Alabama
As for ground straps, yes, all factory ground straps are in place. I tested the ground from the cable at the battery (disconnected) to the distributor and have continuity. I'm starting to question if I have a bad plug wire. That's my next area to inspect.
Thanks,
Keith
Tech Contributor
Joined: Jun 2004
Posts: 20,905
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Update. I pulled the HEI and installed the old distributor. It cranked, but ran almost identical to the DUI that seems to have a failing ICM. Sputtering and misfiring. Then I remembered that I had pulled the ICM from that distributor and used in the DUI to determine the DUI ICM was bad. So I suspect that maybe I had damage the old ICM with the DUI. So I went and bought a new ICM for the old distributor.
I installed the new ICM into the old distributor and it ran exactly the same. Now I'm questioning if the ICM is currently going bad or not. It's acting similar to the last time the ICM went bad, but I haven't pushed it to fail (as I had to do when I was driving to work with the last one started misfiring). Now I'm wondering if the plug wires are weak or something similar that is causing a misfire. I just pulled the plugs and gapped them back to .35 and they all looked good. I confirmed all plug boots are seated well.
What am I missing? I hate throwing money at it, but I'm questioning if I should get a new set of wires and looms. I don't currently have looms, but have them separated using the wire tie trick (wire tie between wires. Don't judge me.).
One thought, now that I'm done working on it for the evening, is it possible I'm off a tooth with the distributor? I have it timed, but I don't know if you can be off a tooth and till time it. I would think if you are off one tooth and have room to rotate the distributor, you could still time it, correct? Maybe this is my current problem with the new distributor.
Any thoughts?
Keith
I installed the new ICM into the old distributor and it ran exactly the same. Now I'm questioning if the ICM is currently going bad or not. It's acting similar to the last time the ICM went bad, but I haven't pushed it to fail (as I had to do when I was driving to work with the last one started misfiring). Now I'm wondering if the plug wires are weak or something similar that is causing a misfire. I just pulled the plugs and gapped them back to .35 and they all looked good. I confirmed all plug boots are seated well.
What am I missing? I hate throwing money at it, but I'm questioning if I should get a new set of wires and looms. I don't currently have looms, but have them separated using the wire tie trick (wire tie between wires. Don't judge me.).
One thought, now that I'm done working on it for the evening, is it possible I'm off a tooth with the distributor? I have it timed, but I don't know if you can be off a tooth and till time it. I would think if you are off one tooth and have room to rotate the distributor, you could still time it, correct? Maybe this is my current problem with the new distributor.
Any thoughts?
Keith
I'm trying to catch up on things in this thread but I recall a problem I ran into years ago. I had a misfire at high loads/WOT, and "everything" seemed to check out okay, but a sharp engine guy said to check the plugs for any open or intermittent conductivity in the center electrode path. Cracks or breaks in that path can cause opens or shorts in the current flow. While plug conductivity issues are rare, I learned they're not non-existent.
Thread Starter
Racer
Joined: Aug 2017
Posts: 352
Likes: 47
From: Bham, Alabama
The cylinders don't care where the distributor is clocked. All they care about is that the plug fires at the correct time.
I'm trying to catch up on things in this thread but I recall a problem I ran into years ago. I had a misfire at high loads/WOT, and "everything" seemed to check out okay, but a sharp engine guy said to check the plugs for any open or intermittent conductivity in the center electrode path. Cracks or breaks in that path can cause opens or shorts in the current flow. While plug conductivity issues are rare, I learned they're not non-existent.
I'm trying to catch up on things in this thread but I recall a problem I ran into years ago. I had a misfire at high loads/WOT, and "everything" seemed to check out okay, but a sharp engine guy said to check the plugs for any open or intermittent conductivity in the center electrode path. Cracks or breaks in that path can cause opens or shorts in the current flow. While plug conductivity issues are rare, I learned they're not non-existent.
Keith
Thread Starter
Racer
Joined: Aug 2017
Posts: 352
Likes: 47
From: Bham, Alabama
UPDATE
I want to start by saying Performance Distributors has been fantastic with trying to help me with the issue. I sent the entire distributor back for testing and it operated perfectly for them. I tested the engine ground at the distributor for voltage drop and it looks good, so my grounds should be good. I will test for voltage drop on my 12 volt power wire to the distributor next. I have a new set of plugs and wires to install as well. There shouldn't be anything else that could cause the control module to fail at that point. I'm hoping I have a bad plug wire and that is causing my issue. I bought some nice wire looms as well and plan to be very diligent with routing and separating the cables.
I'm hoping to get this work done in the next week or so. I'll keep everyone posted.
Keith
I want to start by saying Performance Distributors has been fantastic with trying to help me with the issue. I sent the entire distributor back for testing and it operated perfectly for them. I tested the engine ground at the distributor for voltage drop and it looks good, so my grounds should be good. I will test for voltage drop on my 12 volt power wire to the distributor next. I have a new set of plugs and wires to install as well. There shouldn't be anything else that could cause the control module to fail at that point. I'm hoping I have a bad plug wire and that is causing my issue. I bought some nice wire looms as well and plan to be very diligent with routing and separating the cables.
I'm hoping to get this work done in the next week or so. I'll keep everyone posted.
Keith
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
Thanks for the update!
You might want to consider using your existing but questionable 12V source to act as a relay driver instead. Pull power (through a fuse, of course), directly from the starter, through a Bosch relay, and to your distributor. There will be no question of 12V then.
Also, hook up a digital multimeter to your battery when driving. If your alternator is spiking voltage, you might pick it up.
You might want to consider using your existing but questionable 12V source to act as a relay driver instead. Pull power (through a fuse, of course), directly from the starter, through a Bosch relay, and to your distributor. There will be no question of 12V then.
Also, hook up a digital multimeter to your battery when driving. If your alternator is spiking voltage, you might pick it up.
Safety Car
Joined: Oct 2007
Posts: 4,380
Likes: 1,742
From: Seattle Area Washington
Thanks for the update!
You might want to consider using your existing but questionable 12V source to act as a relay driver instead. Pull power (through a fuse, of course), directly from the starter, through a Bosch relay, and to your distributor. There will be no question of 12V then.
Also, hook up a digital multimeter to your battery when driving. If your alternator is spiking voltage, you might pick it up.
You might want to consider using your existing but questionable 12V source to act as a relay driver instead. Pull power (through a fuse, of course), directly from the starter, through a Bosch relay, and to your distributor. There will be no question of 12V then.
Also, hook up a digital multimeter to your battery when driving. If your alternator is spiking voltage, you might pick it up.
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Thread Starter
Racer
Joined: Aug 2017
Posts: 352
Likes: 47
From: Bham, Alabama
Thanks for the update!
You might want to consider using your existing but questionable 12V source to act as a relay driver instead. Pull power (through a fuse, of course), directly from the starter, through a Bosch relay, and to your distributor. There will be no question of 12V then.
Also, hook up a digital multimeter to your battery when driving. If your alternator is spiking voltage, you might pick it up.
You might want to consider using your existing but questionable 12V source to act as a relay driver instead. Pull power (through a fuse, of course), directly from the starter, through a Bosch relay, and to your distributor. There will be no question of 12V then.
Also, hook up a digital multimeter to your battery when driving. If your alternator is spiking voltage, you might pick it up.
Thanks
Keith
Thread Starter
Racer
Joined: Aug 2017
Posts: 352
Likes: 47
From: Bham, Alabama
****SOLVED*****
I'm happy to report that this issue is resolved and had nothing to do with the Performance Distributor's DUI distributor. They did an outstanding job help me eliminate the distributor as the issue.
This issue ended up being a fusible link at the alternator that was preventing the alternator from regulating the voltage which caused spikes. Another lesson learned the hard way.
Thank you to everyone who provided suggestions to correct the problem. A reminder to everyone, if something seems "off", check it out until it is not. After my polarity issue, my ammeter was not acting right and I assumed I damaged it. Nope, it was right and was identifying the fact that my alternator was not charging correctly. Ugh!
Thanks again,
Keith
I'm happy to report that this issue is resolved and had nothing to do with the Performance Distributor's DUI distributor. They did an outstanding job help me eliminate the distributor as the issue.
This issue ended up being a fusible link at the alternator that was preventing the alternator from regulating the voltage which caused spikes. Another lesson learned the hard way.
Thank you to everyone who provided suggestions to correct the problem. A reminder to everyone, if something seems "off", check it out until it is not. After my polarity issue, my ammeter was not acting right and I assumed I damaged it. Nope, it was right and was identifying the fact that my alternator was not charging correctly. Ugh!
Thanks again,
Keith
