Won't start

DFoley · Posted: Tue Jul 12, 2011 3:37 pm Post subject: Won't start

OK...this is strange. I drove my jeep a few days ago with no problem. Parked her in the garage like normal. Whet to drive her the next day and she will not start. The jeep just cranks and cranks and cranks with not the slightest hint of firing. My normal proceedure is to use the primer pump a time or two to get her to fire up. Now even with the primer pump pushing gas directly into the cylinders it will not fire. I feel as though there is no spark igniting the fuel, but I am not sure where to begin trying to track down this problem. Before i start tearing things appart how should i most efficiently start elliminating possible causes. Any advice would be greatly appreciated.
Thanks,
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Dan
1951 M38

Oldsalt · Member Joined: Jan 28, 2010 Posts: 179 Location: Texas

The quickest way to find out if you have spark is to pull a spark plug wire from a spark plug and hold the tip about 1/8" from some bare metal on the engine while someone cranks it over. Watch for the spark, and you want it fairly dark for that. If you see spark you can look for something else. If there is no spark, check for power going to the coil, but is probably time to do a tune up. Most likely cause is a bad condenser in the distributor, and it is probably time for points as well. If there is no power going to the coil, you will need to find out why. On these old jeeps, crumbling wires is a good likelyhood unless you've renewed the wiring.

DFoley · Posted: Tue Jul 12, 2011 7:55 pm Post subject:

Thanks...I'll check for spark from the plugs first. This jeep has just about had everything replaced and/or repaired, including a new wiring harnes from Vintage wiring harness of Maine. But that has been about 7-8 years ago now. Also new points, capacitor and coil were replaced about 2-3 years ago. How long should I expect these to last. While my jeep is not a daily driver, I do average about 50 miles per month.
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Dan
1951 M38

Oldsalt · Member Joined: Jan 28, 2010 Posts: 179 Location: Texas

Quality parts will last for decades at the rate you drive. I've had my M-38 for 30+ years and never had a problem. Mine gets a similar number of miles. Lube the points occasionally and they will be fine.

On yours even though it has had a tune up, I'd be suspicious of the condenser if it has no spark, but I've also heard that repro coils can be unreliable.

rwbow1969 · Posted: Wed Jul 13, 2011 10:09 am Post subject:

If you leave the on - off switch on by mistake for a period of time you can burn the points, condensor and coil up. It happened to me, lesson learned. Good luck!!!!!!!!!!
Rob
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1951 M-38
1951 M-100
M1919A4

wesk · Posted: Wed Jul 13, 2011 11:33 am Post subject:

First narrow down the system causing the no start. Spark, fuel, air.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

11cgrunt · Posted: Wed Jul 13, 2011 11:44 pm Post subject:

Same problem i had. I ran a wire from the battery ground to the block. Give it a try. It worked for me. Got me running.

Matt R
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U.S Army 1989-2006 Airborne Infantry
8-51 m38
My jeep doesn't leak. its just marking its territory.

DFoley · Posted: Thu Jul 14, 2011 11:24 am Post subject:

OK...here is what I had deduced. There is no spark getting to the plugs. I know this because I took one of the plugs out of the cylinder, left it connected to the plug wire and cranked the engine. No spark was observed. So I moved on to the distributor. I disconnected the power cable (#12) to the distributor, turned on the ignition and tested for power to the distributor with a test light. I was able to confirm power is getting to the distributor. Next I touched the test light to the "+" terminal of the coil and confirmed power to the coil. Then I touched the test light to the "-" terminal of the coil and the test light did not light. Am I now correct in concluding that I have a bad coil? Is there another way to more throughly test the coil? Is the coil a part that has to be purchased from any of the "Willys Jeep" parts suppliers that we all know and love or is this a part that my local NAPA parts store should have. I don't mind mind our jeep parts guys except I don't want to wait for 3 days shipping when I could get the part locally today.
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Dan
1951 M38

RICKG · Member Joined: Aug 31, 2010 Posts: 1741 Location: SO IDAHO

If you're 24V i dont think the napa guy will have a coil on the shelf..
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keep 'em rollin'
RICKG MC 51986 DOD 01-52, '50 CJ3a

DFoley · Posted: Thu Jul 14, 2011 11:54 am Post subject:

Yes my jeep is 24 volts.

I also just deduced that power is getting to the points. With the coil installed and the cylinders turned such that the points open the test light comes on when touched to the mobile arm of the point set. When the points are closed the test light does not light when touched to the points. Now I'm very confussed. For the test light to turn on when touched to the open points, power must be flowing through the coil. So maybe my coil is not the problem. I'm a bit lost here...where should I go from here. If I more fully understood the mechanics of how the distributor, coil and condenser worked I'm sure that would help!
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Dan
1951 M38

RICKG · Member Joined: Aug 31, 2010 Posts: 1741 Location: SO IDAHO

Go to the downloads section under 24V electrical
systems then get to 24V electrical system basics.
The relationships of the electrical components and
how they work together are spelled out in pretty
basic language. Not a quick fix but it will help with
your understanding of the flow of things..
_________________
keep 'em rollin'
RICKG MC 51986 DOD 01-52, '50 CJ3a

DFoley · Posted: Thu Jul 14, 2011 1:53 pm Post subject:

OK... I got her running again. It appears as though the problem was with the points. Apparently the gap had gotten to small and they had got stuck together. Adjusting the gap back to .020 and putting a drop of lubricating oil on the contacts and spring mechanism did the trick.
Thanks for all your help.
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Dan
1951 M38

artificer · Posted: Thu Jul 14, 2011 3:07 pm Post subject:

If this is a standard type distributor

DFoley · Posted: Thu Jul 14, 2011 5:24 pm Post subject:

oh crap...taking the distributor apart sucks. I have too take the air filter off first to get to the distributor. Ok I'll fix my error. How fast imperative is it hat I do this immediately?
_________________
Dan
1951 M38

Oldsalt · Member Joined: Jan 28, 2010 Posts: 179 Location: Texas

There is always a tiny bit of sparking on the points as they open and close. A very tiny bit if things are working properly, but if you have oil on the contacts it will burn to carbon and may or may not interfere with the contacts. It is the rubbing block on the points that needs lube.

Did you do anything to clean the points contacts? If they were actually stuck together you should probably clean them with a fingernail file. Or better yet replace them. They are cheap and it is good insurance.


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