Starter Motor Overrevved?

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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An Old BC
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Starter Motor Overrevved?

Post by An Old BC » Sat Jan 28, 2023 2:56 pm

Greeting Fellow MB/GPW Owners:

Another question concerning my ''42 VEP GPW. I recently replaced the Starter Switch when the old one stopped working. I invested in De Bella's Seal Tested switch. (Ron was out of stock)
It worked great. Light pressure, short throw, good contact.
Yesterday I went to start the jeep in the shop. Half Choke, two pumps on the accelerator, touch the starter switch. All went well. Engine started and I gunned the engine a little and pushed the Choke almost all the way in. It's kind of noisy in the shop with the jeep running but I notices a high rev sound coming from the engine compartment. I checked the AMP Gauge and it was showing almost +60. With that I shut the ignition down and engine slowed down to a stop and the high rev went away. I sat there for a minute wondering what had happened. Turned the ignition back on and hit the starter. Nothing! Watched the AMP Gauge when I hit the started again and noted that the needle barely twitched toward the negative side.
Thought the starter Bendix might have jammed in the flywheel so put the transmission in third and tried to rock it by pushing on the rear wheel. Rocked it a few times and noted no noises coming from the engine. Went to try starting it again and still nothing :( .
My next step will be to pull the starter motor and bench test it but wanted to check in with the Gee folks first.

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Adam
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Re: Starter Motor Overrevved?

Post by Adam » Sat Jan 28, 2023 3:24 pm

+60 on the amp guage says genny and reg are putting out 60 amps to the battery or whatever. Could start switch been stuck?

sounds like bendix came apart and jammed in the flywheel.

this is a 6V system is it not? any chance the starter button got stuck for a bit there?

have a volt meter? does it read 6 volts when button pushed with + on starter stud and - on starter back frame or that ground strap down there.

You will probably have to pull the starter anyway, I just use the analog volt meter first.

Adam

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Re: Starter Motor Overrevved?

Post by An Old BC » Mon Jan 30, 2023 9:19 pm

Thanks Adam:

Sorry I had to wait for my daughter to stop by so I could use her third hand. I can hold the leads on the volt meter but can not push the starter button too :( . She came by tonight so I hassled her out to the shop and performed your test.
I had 6.2 volts across the battery terminals for a base. When I put the positive lead on the + terminal of the starter and the negative lead on the battery's - terminal, the meter showed 5.7 volts. As I watched the meter settle down I notices a light stream of smoke coming up from the starter. Daughter released the button and the smoke stopped.
It was late but I pulled the battery and air cleaner just to see if things were frozen up on the ring gear. After pulling the two mounting bolts the starter pulled right out. No hang-ups that I could hear or feel.
Tomorrow I may bench test the starter with jumper cables and the 6V battery to see if it spins freely and the Bendix rotates out and springs back.
If the starter fails bench test tomorrow I will run it down to the local DC motor shop here in Red Bluff. He rebuilt both the starter and generator when I was restoring the jeep two years ago and does nice work.

Any other thoughts?

Old Retired BC Tim

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Re: Starter Motor Overrevved?

Post by Adam » Tue Jan 31, 2023 5:56 am

Once the smoke comes out it probably will not work. Why wont it turn? either starter bad, most likely,, engine is not stuck is it. very unlikely. Ring gear good, bushing in bell housing good?

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Re: Starter Motor Overrevved?

Post by An Old BC » Wed Feb 01, 2023 8:17 pm

On going saiga of my starting problems.

I pulled the Starter Motor and set it up in the vice to bench test it. Using #4 starting cables and setting the 6v battery six feet away I hooked up the positives and then the negative cable to the battery. I then touched and held the other end to the mounting tab of the starter. It spins beautifully and quietly and the Bendix gear rotated out like it is suppose to. Pulled the negative cable away and the motor stopped and the Bendix retracted with it's spring. Nice to know the starter is still operating!

The Bendix was new two years ago when I had the starter rebuilt and I had a new ring gear pressed on the flywheel. The Bendix gear has some small burrs on its teeth. I felt inside the starter mounting hole and could feel the same small burrs on the ring gear.
After pulling the spark plugs out I used the starting crank to turn the engine. Very easy to turn with the plugs out so it is not bound up.

Other than the starting switch, which was new a month ago and seems to provide power to the starter, what next can I do besides putting it back together and trying to start it again??

Stumped Old Retired BC
Tim

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Re: Starter Motor Overrevved?

Post by Adam » Thu Feb 02, 2023 1:55 am

Wondering if the burrs on the bendix are causing problems, so why would it not turn while in the jeep? maybe file the burrs off and try again? anybody else out there?

ADam

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Re: Starter Motor Overrevved?

Post by OldGPW » Thu Feb 02, 2023 7:16 am

Hi

Did the starter previously function properly when installed in the jeep, or is this the first time you tried it (when it caused the issue that you first posted about)?

If the bendix isn't sticking, then I would want to check the end play and lateral play on the armature shaft, in case it's binding under a load.

I would also not rule out the starter bushing in the bellhousing. They can get worn out and allow the shaft to wallow, or they can be too tight and cause binding.

The smoking was probably from the brushes since the armature wasn't spinning, but it sounds like they are useable since it worked on the bench.
Old GPW.

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Re: Starter Motor Overrevved?

Post by An Old BC » Thu Feb 02, 2023 10:18 pm

Good thoughts Adam. I'll try filing down the small burrs on the Bendix tomorrow.

And good questions Old GPW. The starter was rebuilt by a competent DC shop two years ago and replaced bearings, bushings and brushes. Also a new Bendix gear. No problems since it was installed except that the starter switch (button) gave out. I replaced the switch with a new one from Peter De Bella switch and replaced the bushing in the bellhousing at the same time. All was well for about two months. Then the current problems started.
I'll check for end play in the armature shaft and will check to see if the shaft is pressing against the dust cover on the bushing in the bellhousing. Not sure why that would be a problem especially after two months of starting it 4 or more time each week.

But... You never know until you check it. Thanks Old GPW for the input.

Retired Old BC
Tim

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Re: Starter Motor Overrevved?

Post by An Old BC » Sat Feb 04, 2023 9:30 pm

Thanks again to both you G503ers who offered suggestions on dealing with my 'run away' starter motor. With your advise and guidance I was able to eliminate issues that could have caused my problems.

The high whine I heard when starting my GPW was indeed the starter motor being driven by the running engine. (You know the procedure, when you first start a cold engine using the choke and it kicks over, you run the RPMs up a little to clear the extra fuel out of the intake manifold)

The Bendix didn't disengage from the ring gear and the poor starter motor was being over speeded by the engine. When I shut down the engine and later tried to start it again the Bendix was still stuck on the ring gear. No way for the starter motor to come up to speed with the Bendix engages in the flywheel so. . . . nothing! I would have expected the AMP meter to show a discharge but it didn't even wiggle. Probable something about the starter's draw not going through it.

Solutions you folks suggested that worked:
- Bench tested the starter and found it wasn't damaged. Also Bendix appeared to be working correctly.
- I used a fine flat file to clean up the burrs on the Bendix teeth. I was surprised how much metal had been moved on the teeth.
- I also turned the flywheel 360 degrees in small increments with the crank and observed and felt each tooth for rough edges. There were a few
in one area and I filed them smooth.
- I used white grease to lubricate the end of the shaft past the Bendix and put a little in the bellhousing bushing.
- Reassembled everything including sanding the grounding points.

With the ignition off I pressed the starter button with my hand and presto! The magic sound of a L134 being spun by it's starter.
It was after dark and raining so I will try starting it tomorrow. A few short runs in the yard with multiple starts to make sure the 'sticking' problem has been cured.

Thank you both again.

A Happy Retired BC
Tim

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Re: Starter Motor Overrevved?

Post by Adam » Sun Feb 05, 2023 4:29 am

Amp meter does not read starter draw, starting circuit is a different circuit.
amp meter only reads power from genny going to battery, less what ever is being used for lights, ignition, etc, reading will be + if anything from genny reaches battery,,, if reading is -, nothing or not enough is coming from genny and power being used is coming from battery. For sure everything must be wired correctly, look at the schematic in the tm's

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Re: Starter Motor Overrevved?

Post by An Old BC » Tue Feb 07, 2023 1:00 pm

Thanks Adam:

That all make more sense now. When the Starter started the engine and the Bendix got stuck in the Ring Gear the AMP meter was showing over 25

amps being generated to the Battery to replace the amps being drawn by the Starter. When Bendix was stuck in Ring Gear and I pressed the

Starter, nothing showed on the AMP meter even though there was a direct short through the frozen Starter. Poor battery!

Old BC
Tim


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