coils

[Refit1701]

Awesome, thanks!

[rickf]

John, Thanks so much for the coil report. I have had many inquiries about coils and I have not had any feedback on that batch of coils from Debella. Just curious what the part number is on your Pertronix unit is for the M37? I want to get one for mine.

[John Mc]

John, Thanks so much for the coil report. I have had many inquiries about coils and I have not had any feedback on that batch of coils from Debella. Just curious what the part number is on your Pertronix unit is for the M37? I want to get one for mine.

My electronic ignition is a Pertronix MV-161A. However, this is in a Dodge M37 (251 flathead 6 cylinder engine, 24V system). Just mentioning this so someone skimming this quickly doesn't order one for the 4 cylinder engine in their M151. (Pertronix does make a 24V 4 cylinder version, the MV-141A, but I have no info on whether that is what would be used in an M151.)

It's been several months since I last spoke with Peter Debella, but I made contact several times prior to that and he has not had reports of the coils causing a problem with electronic ignition systems. A local friend of mine rebuilds old Dodge trucks full time. He has put several of the Debella coils in trucks he has rebuilt and has not had any negative feedback on them so far.

[John Mc]

That's good to hear. I have Pertronix in my M37 too. I have heard that it may be a good idea to put a resistor in the line to limit voltages to 24, if your system produces 28ish.

If your system doesn't produce 28ish, you have a problem that's what 24V systems are supposed to produce when running (though 24V systems on some vehicles may need more than idle speed to produce the intended output).

[John Mc]

I just noticed an interesting thing in reviewing the description and installation instructions for the Pertronix MV-161A which is commonly used in M37 trucks with a 24V system:

From the ignition module description:

• Delivers twice the voltage to the spark plugs, increasing horsepower, fuel economy, and spark plug life.
• 2:1 improvement over "points" in current fall time for increased coil output.

Perhaps this helps offset the lower output voltage of the aftermarket coils? I've had no starting problems at all in hot or cold weather. (The coldest I have started it was low 20s˚F.)

From the installation instructions:

The Ignitor is compatible only with a "resisted style" coil. A minimum primary resistance of 7 to 8 ohms is required. (emphasis added)

I'm not sure what happens if you go below that 7 to 8 ohm minimum, but I do know some of these Pertronix ignitions are installed in trucks with NOS coils. Are people doing anything different when using the Pertronix with a NOS coil?

BTW: I have to say that of all the different forums and groups I follow, this is probably the best discussion of coils and options I have found. I really appreciate what people have shared here.

[Refit1701]

I had an after market coil in mine the first big show I drove to. I spent the night and then headed back for the 2.5 hour drive back home. Literally a quarter mile away from the show site (at a state park), suddenly the truck ran like crap. After an hour of diagnosis, the coil had popped and spewed oily crap all over. I spent another night there, cleaning the housing and put an OS coil in it. After that it has been fine.

[Mark]

Oh, those NOS coils are hard to find!!

[Refit1701]

I'll try the the Debella coil when I need one for the jeep.

[rupert's]

Thats a tough one. We all know that the label would be very easy to duplicate and early label and even quick and easy to age it like it was actually old but the the top and case do not match. It almost looks to me like the coil was put together with a new case and an old recycled top. What are the resistance readings on the primary and secondary terminals showing? Original would be around 5 ohms for the stock coil and around 11 ohms for a Chinese coil on the primary windings and if I remember correctly around 10,000 ohms for the stock and 15,000 ohms for the Chinese on the secondary. Primary measurement is between the two small terminals and secondary is between either of the small terminals and the center coil wire terminal.

I bought this coil... To have a spare, I have tried to measure it but I have not come up with anything clear, this weekend I am going to try it on the m151, and I am going to measure the one I have to compare results.

In the upper image it marks 200 OHM and in the upper image 20K OHM

Un saludo

[rickf]

That is reading 7,260 ohms on the secondary and only 1 ohm on the primary. I think the meter is off or just not sensitive enough for that test. But the fact that it is showing what I think is low on both settings makes me doubt the meter. If you hold the leads together does it read zero? Or does it possibly read negative numbers? If you have the manual for the meter see what the procedure is for zeroing the meter for the resistance test. Also make sure you have a good battery in the meter, I have had that happen to me a couple times.

[rupert's]

The coil is defective... I have compared the measurements with the coil I currently have in use and it is clear that the coil is broken.
Also, I put it in the car and it won't start. with the other coil it starts just by stepping on the button.
I have already processed the return for defective. Too bad, it was a good price. Now I have to go back to find a coil to have a spare.

Since it came broken, I haven't been able to find out if it's a NOS coil (it looks like it from the label) or a Chinese coil (it looks like it from the chrome)..

[Redlight]

I have a NOS coil still sealed in the paper wrap on the box. I had it for sale at the MVMVC Weare rally for $200. If you are interested i can find out the cost to ship it.
Thanks
Bruce McCoy (Redlight)

[rupert's]

I have a NOS coil still sealed in the paper wrap on the box. I had it for sale at the MVMVC Weare rally for $200. If you are interested i can find out the cost to ship it.
Thanks
Bruce McCoy (Redlight)

Thanks Redlight, but I live in Spain, I have to buy in Europe, I already have some localized.

[hondo100]

Had a classic coil failure this weekend. M715 quit running and wouldn't start. Luckily, it was in the driveway. Coil was hot to the touch. Last thing I wanted to do was change the coil. So I left it overnight. Next morning it started right up and I moved it in the shop for "deferred" maintenance.

RG

[rickf]

Just so you know the coil normally gets hot when running. And the standard failure routine for coils is they fail when hot an start back up when cooled off. They will do this over and over with shorter run times each time until it no longer starts. This is due to the broken primary wire that pulls apart as it gets hot and comes together as it cools. Every time it pulls apart it arcs so the gap gets larger each time until it just does not go back together.