M38A1 doesn't stay running

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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mdainsd
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M38A1 doesn't stay running

Post by mdainsd » Sun Jun 06, 2021 12:25 pm

I posted this over on Willys but wanted to put it up here to:

This is a new one for me. Helping a friend with his new A1 purchase. Nice original Jeep, no one has monkeyed with anything. Got it home and he cleaned out the tank, when through the carb and checked the initial timing. before we tried to start it we did a compression test as we had the plugs out to replace them anyway. 110 psi down the row.

Starts right up, sounds good and dies at 2 seconds in. It does this every time.

We fooled around with it a few times same result. Today we ran a jumper from the battery to the distributor just to rule out flaky wiring somewhere. Same thing.

Just for kicks i suggested disconnecting the two cables at the regulator. Guess what? Starts up, keeps running and sounds awesome. Ran out of time for the day.

While I have never come across this I will go into the generator and regulator with the meter next time. Seems whats happening (not yet verified) is what the engine comes up to speed the generator cuts in and apparently that is shorting the system. Of course as soon as the engine stops the fault clears and you can start it up right away and it dies again. My "guess" and that is all it is at this point is that the armature is shorted to ground in the generator or the connecting cable. Regulator cuts in hooking the armature to the system which kills the system. We will see...

Interesting problem, wondering if any of you have ever run into this one. We have spare generators and regulators so it won't be a problem getting the Jeep running. I just want to dig further and pin point the failure mode.
52 M38 2X, '52 M37, '44 WC51, '42 WC 56/57, '50 CJ-V35(U), '42 GPW, '44 M3A1 Scout Car, 2010 M-Gator


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