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willysmjeeps.com :: View topic - Need help with starter problem
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Need help with starter problem
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wesk
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Location: Wisconsin

PostPosted: Sat Jun 27, 2020 9:30 am    Post subject: Reply with quote

The reason I advised him to disconnect the armature was to prevent the armature from turning by restricting electrical activity to the solenoid only. When trying to measure bendix travel with a starter laying on your bench spinning and developing a turning torque is a real PITA!

He has already tried sparking 12V to the small terminal. I believe he has a start circuit that actuates the solenoid by grounding that terminal.

Trying to help someone troubleshoot a Bendix engagement problem who has a late 40's Chevy 6 volt starter converted to 12 V on his M38 which is also converted to 12V and has eliminated the kick start pedal with a key start switch is very difficult when I am unable to see the wiring of the key start circuit nor can I find a copy of the internal wiring diagram of his converted starter.
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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
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32sbct
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PostPosted: Sat Jun 27, 2020 1:21 pm    Post subject: Reply with quote

Wes I agree 100 %. There are so many variables at play here. Diagnosing this one over the internet is a tall order.

All, my solenoid has three terminals. A large terminal for the cable that goes directly to the positive battery terminal. The negative battery cable is grounded to the engine block. There are two small terminals marked S & R. The S terminal (to the right of the large 12 volt terminal when viewed from behind) is wired directly to the ignition switch. The R terminal is to the left, I don't have the R terminal wired to anything. The wiring harness was a new made CJ3A wiring harness sold by Walcks 4WD that they modified for key start and turn signals.

Just to recap

1. The flywheel is a late M38 129 tooth which was in excellent condition. The front edge of many of the teeth are being damaged by the starter bendix.

2. The starter is a non standard item. It has a 9 tooth bendix. At rest, the bendix is 3/4 of an inch from where the starter housing touches the bell housing to engine plate. The bendix itself is 3/4 inch long. When activated it extends 1 1/2". I can only get it to extend when doing the normal starter test.

3. The measurement from the back side of the flywheel to the bell housing to engine plate is 1 1/4 inches.

If my calculations are correct the bendix should be engaging the flywheel dead center with 1/4 inch extra to spare on its front and back.

However for some unknown reason it sometimes hits the front edge of the flywheel.

I'm at a loss on what to try here. There is only one way to bolt it on.
When I test it the bendix it smacks the front of the casting an spins super fast.

Barring any other ideas, I'm guessing at this point I'll look for a new starter. I think the damage to flywheel is light enough to use as is. If anyone thinks thats going to be an issue please let me know.

Based on the fact that's its a non original key start 12 volt jeep I'll probably try one of the new high torque 12 volt starter motors adapted for an M38. It will look totally out place but other options get pretty expensive since I don't have a core to trade.

I really appreciate everyone's input. It's interesting that once the stater was identified Wes was able to find its use somewhere in the Army's fleet.

Thanks Again,

Marty
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wesk
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PostPosted: Sat Jun 27, 2020 8:41 pm    Post subject: Reply with quote

Marty,

Keep in mind that jeep was set up for a Starter that used your foot to engage the bendix with the flywheel BEFORE anything started turning. With the Chevy starter the instant you apply power to the solenoid the power is simultaneously applied to the armature this starts to move the bendix towards the flywheel but the bendix is already spinning. The smart choice here is the correct starter. Since you are set up for no foot pedal just use one of the original jeep 12 volt starters like the MDU-7004.

You should file dress each damaged tooth on the ring gear.
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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
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32sbct
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PostPosted: Sat Jun 27, 2020 9:59 pm    Post subject: Reply with quote

Wes, I must be getting a little smarter. I was thinking the same thing earlier today when I was testing the starter again. You are spot on, the bendx starts turning full speed the second it gets power. I'll start looking around for starter you recommend and let everyone know how it tuns out.

Thanks, Marty
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4x4M38
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PostPosted: Mon Jun 29, 2020 7:21 am    Post subject: Reply with quote

Question.

Does the civvy MDU-7004 move the Bendix forward then start it spinning, or does everything happen at once like that Chevy starter he has?
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Brian
1950 M38
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wesk
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PostPosted: Mon Jun 29, 2020 9:22 am    Post subject: Reply with quote

The Chevy starter does not start everything at once. The solenoid takes longer to extend the Bendix then the initial spin up time of the armature. The Bendix is mechanically extended by the solenoid.

The MDM starter has a rapid moving bendix that inserts itself into the flywheel on the first full rotation of the armature.

I assumed all you bright guys out there already knew the differences between these ancient starters! Confused
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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
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4x4M38
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PostPosted: Mon Jun 29, 2020 3:59 pm    Post subject: Reply with quote

Ha!
Just because we are Bright doesnít mean we know everything!!

Iíve got a 7004 so wanted to know.
That is really good info.

Thanks!
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Brian
1950 M38
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