Re: Starter rpm/M37


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Posted by Alan Bowes on February 08, 1998 at 19:31:41:

In Reply to: Starter rpm/M37 posted by Joel Foley on February 08, 1998 at 09:09:52:

While there are several possible causes of slow cranking (if it actually IS slow), one of the more common ones with an M37 stems from problems with battery cables.

Because of the long cables, it is important that very heavy-gauge cables are used, that the connectors make good contact with all strands of the cable, and that the connectors are making good contact with the battery posts. Naturally, all other connectors in the starter circuit must be up to snuff as well.

You can check the voltage drop across the cable that goes between the battery and the starter switch. Connect the + voltmeter lead to the + battery post (not the connector). Make sure you get a clean contact against the lead post. Scrape some oxidation off first. Connect the - lead to the terminal on the starter switch. Crank the engine. You should not have more than about 2/10 (.2) volt reading. If it is higher, there is too much voltage drop across the cable. Check all connections carefully.

Also check the connections and cable connections of the battery ground and inter-battery cables. Then perform the same voltage-drop test on the starter ground circuit: Connect the negative voltmeter lead to the negative (ground) battery terminal and the positive voltmeter lead to a clean spot on the starter motor frame. Crank the engine. There should not be more than about 1/10 (.1) volt reading. If it is higher, you may have a problem with cables or connections.

Another factor is the cold-cranking amp rating of your batteries, as well as the charge on them. You might borrow a couple of larger batteries just to compare the results.

Of course, the starter itself could require servicing, or there could be an alignment problem between the starter pinion gear and the flywheel ring gear.

TM 9-8030/TO 36A-1-411 has instructions for testing and servicing the starter motor.




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