Symptoms of a dying coil?

Jim · Post by **Jim** » Sat Nov 14, 2009 4:07 pm

I'm trying to track down why our M38 just flat quit
whilst idling in the driveway. Previously I replaced
the carb with a rebuilt one from Midwest, and the 'bubba'
fuel filter, and the condenser. The puffing black smoke
stopped with the carb change. It was still running rough
with a lack of power, and a bit of blue smoke, when it
just died.

Would a dying coil exhibit these symptoms?

The points do not seem to be pitted. It tries to start
now, but won't. It is getting gas from the odor.

I missed the Veteran's Day Parade, although our
Arkansas MVPA had three M35's and a pickup there.
Drat!

Jim in Darkest Arkansas

Post by **wesk** » Sat Nov 14, 2009 9:07 pm

Hello Jim,
It's easy to get overwhelmed or intimidated but problems like these. You'll have to give us a little more to work with.

Tries to start

Can mean a lot of different things to different people.

Does the starter spin the engine over at normal speed?

Can you hear the engine firing occasionally?

Is the gas tank reasonably high enough to support a running engine.

Jim · Post by **Jim** » Sun Nov 15, 2009 8:01 am

Thanks, Wes. Yes, the starter spins the engine
normally, it fires occasionally, just not enough
to 'catch' and keep going. The gas tank is 3/4
full.

Jim in Darkest Arkansas

Post by **wesk** » Sun Nov 15, 2009 9:02 am

If it fires occasionally then there is coil life somewhere and it may be fuel or ignition or air still.

You should use the troubleshooting charts in your service manual for engine cranks but will not start. A simple ignition check is to remove the plugs and srew their leads back onto the plugs. Then lay them on the engine and have a friend crank the engine while you closely observe the plugs. If they all spark and repeat the cycle at a regular interval your problem is not spark. If they spark intermittently without any apparent order then check the main coil power lead at the side of the distributor to make sure it is tight. If it is ok try removing the cap and check that contact point gap is correct and then that the points are actually opening and closing as the engine turns and the points are tight to the base. If this checks ok then check the wires too and from the coil for cuts and tightness. If that's ok then check the coil itself with the wires disconnected with an ohm meter for primary and secondary resistance.

mtdave · Post by **mtdave** » Mon Nov 16, 2009 8:47 am

Wes that's some really good info. My M38 sort of did the same thing, was running fine one day back-fired and died. It was tune-up time so I bought coil,cap,rotor,cond, and removed the civi plugs and wires and put the right ones on. It still wouldn't start so I talked to my mechanic and he said there is a break in the circuit somewhere. To test I unscrewed the hex plug out of the dist. cap and ran a hot wire from the +side of the coil to the +battery terminal. She fired right up and purred like a kitten. So with your diagrahm I know where to start looking.
Here is my problem I wanted to print your pictures and explanation so I could have it right next to me while testing but your post is bigger then my screen. Hey computer geeks how do I shrink it to page size?

Post by **wesk** » Mon Nov 16, 2009 11:44 am

Hello Dave.

Download the photo to your computer by saving it as " whatever you choose to name it" in the file folder you choose. Then open it with your photo working program and resize it. If you are not sure what you have for a photo working system check with your local computer geek.

Jim · Post by **Jim** » Sun Feb 28, 2010 5:36 pm

Looks like a new coil did the trick. Replacing the
condenser didn't do any good. Got a new coil from
Midwest and put it in over the weekend, and she
fired up today. First run since November. I'm going
to run it several times in the garage before taking
it out on the street. The old coil had lots of different
numbers and some yellow paint on it. Perhaps it was
original to the vehicle. Thanks, John!

Jim in Darkest Arkansas

Jim · Post by **Jim** » Fri Mar 19, 2010 7:54 am

Technical Data on the coil removed. Silver case,
brown plastic top with the words "Made in U.S.A"
Label about half-way down the side, bordered in
black with black letters on white background, in
three lines: System
24 Volt (larger print)
System

Numbers under and near the bracket in one line:
MS1114 CY-4002 24V 12X

There is a 'dab' of yellow paint to the right of these
numbers.

There are two 'scorched' carbon areas on the lower
part of the case. There doesn't seem to be a burn-through.

Currently the M38 starts and runs OK, but has little
power under load. I'll be working on this problem
with help from the manual, and possibly from friends
in the Arkansas MVPA.

Jim in Darkest Arkansas