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Ignition gremlins in a 225ci
https://slantsix.org/forum/viewtopic.php?t=67843		 Page 1 of 1
Author:  doubleclutch [ Tue Jul 23, 2024 7:09 am ]
Post subject:  Ignition gremlins in a 225ci
I have an '85 Dodge D100 with a 225ci and I've run into some ignition gremlins. The ignition type is a firewall-mounted ignition control module with a single pick-up inside the dizzy. The ballast resistor was deleted before I got the truck and modern ignition parts (E.G. the Pertronix coil) clearly state the resistor does need deletion. I'm inclined to believe the resistor isn't necessary because it ran fine for the previous owner and also ran fine for me, at least until it didn't.
I ran multimeter tests at the 4-cavity ICU plug and all show proper voltage and resistance, according the the specifications in my period Haynes manual. This seemingly also confirms the following:
- Proper battery voltage
- The key/ignition switch must be working
- The dizzy pickup is working, since it shows 240 ohms resistance (within spec)
- Proper voltage is being sent to coil primary
I then did some testing at the coil and found the following:
- There is no spark coming out of the high tension wire while attempting to start the engine
- Coil positive is receiving proper battery voltage though
- I pulled the coil and tested it for spark on a bench with a battery and a spark plug and it does work
I've also bench-tested the coil a few times with a multimeter and it is within spec, which is expected since it's a brand new Pertronix. (more on this coil later..)
I've tried two different Ignition Control Modules, both are new and confirmed to be grounded properly to the firewall since I verified per the specified multimeter test in the Haynes manual.
A common issue for this era was the amp gauge, however that isn't a factor since it was bypassed before I got the vehicle. Also, it can't be the problem because power is flowing per my described tests.

Here are my questions for someone with far more experience than myself since I'm at a loss what to try next:
- This Pertronix coil is 1.5ohm. This is within spec according to the manual, HOWEVER, the manual assumes a vintage setup with ballast resistor. I didn't discover until after I encountered this problem that Pertronix specifies only their 3.0ohm coil for six cylinders (sans ballast resistor). I'm wondering if this difference in resistance is the root of the issues, though it did run with this coil for a time.
- This seems like it could also be the Ignition Control Module, though I've already tried two of them and neither resolve it. But..I'm not versed on electronics and the thought I have is maybe that 1.5ohm coil is causing issues with the ICUs? If that's possible, I would like to understand how that might be the case (E.G. how the current flow would cause the ICU to burn out or fail from a mismatched coil since I currently understand the ICU simply closes the coil circuit each time it needs to fire)

It's a long message but there's a lot of troubleshooting already done, so wanted to share it all.
Author:  MadScientistMatt [ Sat Jul 27, 2024 10:30 am ]
Post subject:  Re: Ignition gremlins in a 225ci
Is this a stock type module or something aftermarket? Stock type is going to need a ballast resistor, no exceptions.

(Not counting oddities that plug into a stock harness but are definitely not stock inside, but you will probably know if you have one of those.)
Author:  Charrlie_S [ Sat Jul 27, 2024 11:03 am ]
Post subject:  Re: Ignition gremlins in a 225ci
Quote:

- The dizzy pickup is working, since it shows 240 ohms resistance (within spec
That just means there is continuity. Is it the stock factory distributer pickup? If it is disconnect the plug and connect it to a volt meter (analog is best) crank the engine and see if you get a low voltage reading. (I think less that 1 volt)
This is a great tester for early electronics. If you buy one, make sure it comes with the instructions. Not hard to use, but the instructions make things super easy.
https://www.ebay.com/itm/135108602989?e ... BMhpvX1Z5k
Author:  doubleclutch [ Sun Jul 28, 2024 6:06 am ]
Post subject:  Re: Ignition gremlins in a 225ci
Quote:
Is this a stock type module or something aftermarket? Stock type is going to need a ballast resistor, no exceptions.

(Not counting oddities that plug into a stock harness but are definitely not stock inside, but you will probably know if you have one of those.)
Thanks for your feedback.
The module(s) aren't original (of course) and are generic. They are both new.
As mentioned, it's been running without the resistor for years between myself and the prior owner. You sound confident in your point though - I'm eager to learn how the resistor would impact the module? The coil requires deletion of the resistor so that creates a chicken and egg situation. Also, where do you think my problem is, with the assumption that a resistor would only help prevent a recurrence?
Author:  doubleclutch [ Sun Jul 28, 2024 6:09 am ]
Post subject:  Re: Ignition gremlins in a 225ci
Quote:
Quote:

- The dizzy pickup is working, since it shows 240 ohms resistance (within spec
That just means there is continuity. Is it the stock factory distributer pickup? If it is disconnect the plug and connect it to a volt meter (analog is best) crank the engine and see if you get a low voltage reading. (I think less that 1 volt)
This is a great tester for early electronics. If you buy one, make sure it comes with the instructions. Not hard to use, but the instructions make things super easy.
https://www.ebay.com/itm/135108602989?e ... BMhpvX1Z5k
Actually, you answered a question I've been struggling with - how to test the Ignition Modules since the only method I could find is vintage 70s and 80s manuals that suggest your local dealership could test them with a special diagnostic machine. Looks like this could be the modern version. I'll need to grab one.
Author:  Charrlie_S [ Sun Jul 28, 2024 6:33 am ]
Post subject:  Re: Ignition gremlins in a 225ci
Quote:
Quote:
Quote:

- The dizzy pickup is working, since it shows 240 ohms resistance (within spec
That just means there is continuity. Is it the stock factory distributer pickup? If it is disconnect the plug and connect it to a volt meter (analog is best) crank the engine and see if you get a low voltage reading. (I think less that 1 volt)
This is a great tester for early electronics. If you buy one, make sure it comes with the instructions. Not hard to use, but the instructions make things super easy.
https://www.ebay.com/itm/135108602989?e ... BMhpvX1Z5k
Actually, you answered a question I've been struggling with - how to test the Ignition Modules since the only method I could find is vintage 70s and 80s manuals that suggest your local dealership could test them with a special diagnostic machine. Looks like this could be the modern version. I'll need to grab one.
That tester is no longer made. But it is a great unit. I have been using one for years, and about a year ago I bought a spare of E-bay. Very inexpensive, easy to use, and works on just about anything except the computers themselves. Basically a "go/no go" tester. Has two led lights as indicators.
Author:  doubleclutch [ Wed Aug 28, 2024 2:48 pm ]
Post subject:  Re: Ignition gremlins in a 225ci
I'm the OP and just leaving an update and some useful information for my future self and other forum readers to take advantage of.

I purchased the Sunpro Sensor Tester suggested in this thread by Charrlie_S and if you can find one, I found it quite useful. At the time of this posting, you can find vintage models on eBay for between $20-$50 but BE SURE YOURS COMES WITH THE MANUAL since I encountered a seller that sold me a "New in box" unit that was anything but and the worst part is it didn't even have the manual. A PDF version of the manual is nowhere to be found online anymore, even from the manufacturer. So, I sent that one back and have a good unit with a manual and I'm keeping it in my tool kit, indefinitely. Also, as Charrlie_S suggested, this is just a go/no-go tester so it may not always help you pin down your particular issue.

That leads me to what I believe my issue is, though I haven't received the parts to confirm yet. Regardless, I think this is info worth keeping for future readers.
After combing too many manuals, forums and videos to count chasing these problems, I finally found this particular video:
https://www.youtube.com/embed/tVja7UctgIw
Though my ignition module tested fine with the Sensor Tester unit mentioned above, an issue I discovered from this video is that neither of the ignition modules that I have in-hand are putting the required voltage (.5 volts) on the distributor pickup wire (the gray one going to the reluctor). Neither of the units that I have are are even close to that. This video is the only place I've found this test, after reading over numerous old shop manuals, forums, videos, etc etc.

Both of the ignition units I have are "new" units, but I understand these are all largely trash from China. The first thing I suspected when having this issue was my ignition module and so that's why I got a second one but it's clear it isn't any good either. I found Rock Auto has a so-called Blue Streak unit for sale - I know they aren't the quality USA products anymore but finding a new old stock ignition module is impossible. Fingers crossed.
Author:  SlantSixDan [ Wed Aug 28, 2024 3:36 pm ]
Post subject:  Re: Ignition gremlins in a 225ci
1. Try switching the ignition On, then activating the starter by means other than twisting the key—such as by carefully using a screwdriver to connect the large and small terminal on the starter itself, or the largest and second-largest terminals on the starter relay.

2. Study up on the HEI upgrade .
Author:  doubleclutch [ Sat Aug 31, 2024 4:15 pm ]
Post subject:  Re: Ignition gremlins in a 225ci
Quote:
1. Try switching the ignition On, then activating the starter by means other than twisting the key—such as by carefully using a screwdriver to connect the large and small terminal on the starter itself, or the largest and second-largest terminals on the starter relay.

2. Study up on the HEI upgrade .
I'm using a remote starter button since I can't be under the hood and at the ignition switch at the same time, so looks like I'm accomplishing this suggestion albeit a different way.

I did have a conversion in my back pocket in the event I draw snake eyes with my "new" ignition parts. I didn't realize this HEI conversion was on the forum, so I certainly appreciate the link!
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