Power to starter when switch is off

[Madriver1968]

Hi all, I have a 1954 M38a1 and I’ve just installed a new wiring harness I purchased from Pete Dabella. System is 24 volt, and I’ve made no modifications other than a solid state voltage regulator. No accessories and I have not installed any circuit breakers. Everything is wired per the wiring diagram in the manual and I’ve carefully matched all numbers on the harness.

Today, I decided to try everything. I turned in the switch, and all lights and panel lights work as they should. I pushed the starter and the engine turned over. I was quite pleased until I turned the on off dash switch off, and pushed the starter foot switch, just to check that everything was off. Unfortunately, the starter engages!

I removed the switch, thinking it might be the problem, but even with the on off switch completely unplugged and removed from the vehicle, if I push the starter foot switch, the Jeep turned over!

I clearly have a short somewhere. Any suggestions of where to look would be most appreciated. Thanks!!

[OKCM38CDN]

There is always power to the starter. The foot switch opens taking the power off the motor in the normal position. When engaged (Pushed) it supplies power to the starter and turns the motor over, if the ignition switch is turned on the motor will start. If the ignition switch is not on the motor will not start.

This is the way even modern cars work except in modern cars the foot switch is replaced with a solenoid that engages the motor to turn the motor over...

All is working as should in your jeep. Look at the schematic in the manuals...

[wesk]

You were close Hal but the M38 is not like the modern cars.

In the M38:

The switch on the dash is a master switch and only applies power when on to accessories and the ignition system coil.

The starter switch is always hot. (Not the dash switch the one on top of the starter.)

The starter drive is engaged manually with the flywheel using the foot pedal. The foot pedal is adjusted so that when the starter kick pedal completely engages the drive with the flywheel then it bumps the switch contacts closed and they turn the starter motor.

So mad driver this is one reason that it is a good idea to install a battery disconnect switch on your M38. This way when the kids jump in and want to play "push the starter pedal" you don't have to worry about the jeep leaping forward because the starter is turning the engine and the engine is turning the tranny which you left in gear to hold the jeep still but now the jeep is lurching forward! The other good reason for the battery disconnect is it will save your ignition coil when you forget to turn the dash switch off.


In modern cars :

The switch on the dash is used to turn on accessories, power the ignition system and close the starter solenoid (relay).

The starter has no power to it when the dash switch is in acc - off - on. When the dash switch is moved to Start position then the solenoid (relay) closes and power is delivered to the starter.

Once the starter is spinning it's rotational motion spins the starter drive towards the flywheel to engage it and turn the engine.

[4x4M38]

Wes,
Is the later starter (129 tooth flywheel) different with respect to the pedal pushing in the starter to engage the flywheel? I had to replace my Bendix in my later starter. Does the early starter not have a Bendix?

A battery disconnect is a good idea for several reasons.

[Madriver1968]

Thanks gents! I appreciate the info. I was confused because the two old cars I have that have separate on-off switches and starter buttons don’t work that way. On both my Healey and my Jag, the starter buttons are not always hot - if the on-off switch isn’t turned to on (in those cases it’s the key, which only has two positions, on and off), then pushing hr starter button does nothing.

First thing I do with any old car is install a battery cut off. I’m always amazed how many guys I see at meets that don’t have them. Seems like asking for trouble.

[wesk]

Is the later starter (129 tooth flywheel) different with respect to the pedal pushing in the starter to engage the flywheel?

Not really. The pedal still does the same thing. It pushes the starter overunning clutch/pinion drive into engagement with the flywheel making the switch close at the same moment the drive is beginning to mesh the pinion with the flywheel and then the starter spins.

It is common for folks to be tempted to refer to all starter drives with the same name "Bendix" . Also most folks do not realize that the Famous Auto-engage Bendix Drives eventually fell from the favor of the automakers because of it's heavy gear tooth wear issues and now most modern cars use a dual purpose solenoid mounted to the starter that when power is applied to these newer solenoids the shaft, as it starts to move to close the electrical contacts also moves an overunning clutch drive to engage the flywheel then closes the contacts spinning the starter.