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I have a M37 that a previous owner converted to a non resister ignition system with negative ground. I'm not getting any power to the plugs and must be overlooking something. The civilian regultor is new as is the coil and I have changed the distributor with one out of a running truck along with the plug wires. All the wires look new and it is wired like a WDX except for the neg ground. Anybody have any ideas
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When you say you are not getting power to the plugs, I gather you mean no spark at the end of a plug wire?
Does this truck have the original M-series distributor?
If it had a conventional distributor, I would say let's disconnect the coil wire from the center of the distributor cap, hold it near a ground, and manually open and close the points as the ignition switch is in the ON position. ....to see if you can get a spark jumping from the end of the coil wire.
I may have an M-series distributor in my shop, I will try to go look.
Other M-series guys should be along shortly....Power Wagon Advertiser monthly magazine, editor & publisher.
Why is it that the inside of old truck cabs smell so good? -
12Volt M37
Gordon, thanks for the diagnostic tool. The distibutor is a civilian conventional and I tried removing the coil wire from the cap and got no spark while working the points. The + side of the coil was hot with nothing on the - side. Is the coil bad? It's supposed to be for a non-resister system or should I just install a resister and conventional coil. Years ago, I put a Chevy V-8 into a M37 using the resister system and never had a problem with it.Comment
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Generalizing, 6 volt systems did not have ballast resistors; 12 volt systems did. The resistor — in a system having one — either took the form of a separate component or was incorporated into the ignition coil. You would not want to make the mistake of using an inline ballast resistor in conjunction with a coil having an internal one. The fact you don't see a resistor does not mean you don't have one.Originally posted by kodiak2 View Post
Make sure your condensor lead is well connected and the ground strap is clean and tight. It is quite unusual for a condensor to actually go bad.
It would be good to check your coil wire with an ohm meter to make sure it is not open. That could prevent a spark.
Also visually inspect the inside of the distributor cap and the rotor for cracks and carbon tracks. The presence of either of those things could cause the spark to go somewhere other than where you want it to go.
Let's not buy a coil just yet; let's eliminate some other possibilities.Power Wagon Advertiser monthly magazine, editor & publisher.
Why is it that the inside of old truck cabs smell so good?Comment
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12Volt M37
Hi Gordon,
I tried the coil wire and found it ok. I plan to install new points and condenser with a new cap and see what happens. The latest issue of SKINNED KNUCKLES has a way of checking a coil which I will try also. Still have no power going from - terminal on coil to dist.Comment
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Using an Ohm meter with all the wires removed from the coil, place the negative test lead on the negative terminal. When you touch the positive test lead to the positive terminal you should read between 0.8 and 4.0 ohms. When you connect the positive test lead to the secondary (high tension) terminal you should read between 6,000 and 18,000 ohms. Try this again with a cool that has been warmed up with a heat gun to make sure it doesn't break down when warm.
The old round coil nomenclature can get confusing sometimes. From the early 20's to the 50's coils were all 6 volt. When 12 volt systems showed up in the 30's on a few cars so did the external ballast resistor. This resistor reduced the 12 to 14 volts to 8 to 9 volts. When 12 volt cars got more popular in the mid 50's the coil makers got a great idea. Lets call our coils 6 Volt, 12 volt (Use with external resistor) and 12 volt. The 6 volt unit is the same old coil since the late 20's. The 12 volt (use with external resistor) is the same old 6 volt coil with 12 volt stamped on it. The 12 volt unit is different. It has the resistor built inside of it.Comment
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12 volt M37
Thanks guys. I tested the coil and even took it into town and had it verified at an automotive electrical shop. I then changed the points and condenser and found that I had spark on the coil wire!
I then found the electric fuel pump would run but didn't pump any fuel; and the oil filter sized OMC fuel filter was dry. I found all this out looking down the carburetor while my wife pushed the starter button.
After getting off the fender and transferring her foot from the hi/lo beam switch to the correct starter "button", I found no fuel entering the carburetor. I tore all this stuff out and installed a conventional fuel pump and blew out all the fuel line back to the tank.
It actually started right up once it got fuel and ran quite well even with the severe engine knock. I guess you win some and lose some!Comment
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Congratulations on your success and tenacity. Great job!Power Wagon Advertiser monthly magazine, editor & publisher.
Why is it that the inside of old truck cabs smell so good?Comment
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credit due
Thanks Gordon, the fact is if it wasn't for you and the other gentleman in the forum, I'd still be fooling around with this. I have pulled another donor vehicle up next to the M37 which had a running engine in it when I bought it a few years ago. I will have the knocking engine rebuilt and place that in a WDX I'm hoping to restore. Thanks again and keep up the excellent work in the forums.Comment
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