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Voltage loss at the starter - Farmall M gas

S

Scott Flynn

New User
My tractor will not turn over. I have 12.2 volts reading at the battery posts. When I hit the starter switch the starter groans just a bit and then quits. When I read the voltage at the battery posts when I hit the starter switch, the voltage drops to 3.8 volts. Not sure what to do or where the problem is. Any help would be appreciated. Thanks
PS - Battery is a year old and had starter rebuilt a year ago. Replaced starter switch too.
 
The issue is one of two things. Either there is high resistance in the wiring/switch going to the starter, or the battery is bad.
The battery voltage should be near 12.6 across the battery terminals. The voltage measured across the terminals when cranking must stay above 10.9 volts. (a little less is OK) If the voltage reads very low there, the battery is either low on charge, or bad.
If the voltage is good follow the voltage with your meeter (new starter switches are notoriously bad these days, and may even be getting hot)
Cables should be at least )gauge copper and soldered on connectors shiny and bright. Let us know what you find. Jim
 
I had a similar situation on my JD430 a while back. Battery would barely roll engine. I put charger on it and it showed battery at full charge. I was sure it couldn't be the battery as it was only a month old. After tryng a lot ofunnecessary stuff, tried another battery and it rolled over fine. Apparently a bad cell in new battery.
 
Thanks to all of you who answered so quickly. I'll check your ideas out and get back to you when I'm either fixed or in need of more help.
Regards - Scott
 
Remove the starter and clean where it mounts and also check and clean the battery cable connections. I'll bet you have a not so clean and tight problem some place be it where the starter mounts or a battery cable. Can also be the ground cable where it mounts to the tractor. Getting it as close to the start works the best as in maybe even a starter mount bolt
 
You might want to have the starter cked/rebuilt. A friend of mine had the same problem, we removed the starter and found the bearings and cone bushings bad. He had the starter rebuilted and everything is good now. Good luck
 
You might want to have the starter cked/rebuilt. A friend of mine had the same problem, we removed the starter and found the bearings and cone bushings bad. He had the starter rebuilted and everything is good now. Good luck
 
A couple possibilities:

1 - The starter pinion is jammed in the ring gear.

If you can move the tractor, stick it in 5th gear then rock it BACKWARD and inch or two. If the starter is jammed a "clunk" from the starter as it is rocked means it has freed itself up. OR......loosen the starter mounting bolts and pull the starter part way out of the bell housing. Again a "clunk" will tell you when the pinion is again free.

2 - Your battery is low.

A good, fully-charged battery will show 12.6 at rest. Your reading of 12.2 (assuming your voltmeter is accurate) is somewhat low. Also your 3.8 volt reading under load is low - a good battery will show at least 8 - 9 volts with the starter engaged. Try charging the battery overnight, or better yet jump the tractor from a running vehicle.
 
Thanks - I tried jumping the tractor from my truck. Had the jumper cables on it for an hour and no luck at all. Before that I had the charger on it for a couple hours and neither worked.
Regards - Scott
 
I agree with Bob. My 1950, Farmall M, gas, sticks the pinion on flywheel all the time. Especially, if battery low.

Take post off battery. Spin radiator fan 1-2 times in neutral, see if cranks. Otherwise, can take the 2, I believe 9/16" bolts , to unbolt starter to frame. Touch terminals of starter to battery only, not another vehicle, see if Bendix gear spins fast? Otherwise, if stored outside, fresh battery, always a good start. Also, is very likely original brushes in that starter? Fresh battery, + fresh starter eval. helps avoid lot of cranking. (Learned that hard way 5 years ago, on JD 4020).

Good Luck! Great tractor, mine runs great most of time. Don't get discouraged!

Matt
 
Sorry, just reread where you had starter rebuilt 1 year ago. I concur with battery voltage.
Let us know what you find.

Matt
 
try cranking it a couple times then.....CAREFULLY....feel the battery cables and ends to see if they are hot anywhere. if so, you have found your bad connection. on one of my m's, i had to run the ground directly to the mounting bolt on the starter . apparently, after 60 some odd years, the tractor chassis doesnt have a good ground path anymore.
 
Yep always start with the simple duh type stuff and then work to the harder stuff. Reason I say duh is because many times it is as simple as a battery cable that is not good and tight and clean
 
I had one that done that and it turned out to be a bad cable. I knew this because I could put jumper cables staight on the starter lug and it would spin over. That is what I would try first. Its fast and easy to check.
 
You are measuring at the posts, (not the clamps on the posts) and you are dropping from 12.2 V to 3.8 V.

There are two things that can cause this, the battery does not have sufficient remaing capacity to maintain 11 V while cranking or the load in the starter circuit is greater than what the battery can keep up with.

So, bad battery or a dead short.

Some times you can pull the caps and observe the water in the cells. If one is bubbling a bunch you have a bad cell.

Good luck.
 
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