electrical problem help

I have a M farmall When I hit the starter all I hear is starter turning but not engaging . The top post on my solenoid starter switch has power but when I hit and hold the solenoid the bottom post still don't have any power. The bottom post should have power correct . But when I check to see if I have power to nthe starter .none but the starter turns. Thanks Plow Boy in OK.

If the starter turns, you have power to both large terminals on the solenoid when you actuate the switch.
Sounds like your "inertia" powered Bendix needs cleaned as well as the helix on the starter shaft.
Pull the starter & see what the drive end looks like. Also check it out on a bench using a jumper cable. Observe the Bendix action. Let us know.

To be sure we are on the right track, and with respect: A starter switch with a big button and two big terminals, that requires a solid "pushing in" to make a connection is just a starter switch, not a solenoid.
A smallish roundish device that looks like an overgrown film canister with two big terminals, and one or two smaller terminals, and no mechanical connection to the gears of the starter, is properly called a Starter Relay. (it is often called a solenoid, but it is not)
A usually cylindrical device that is responsible for both turning on the starter current, and pushing the drive into the ring gear with a mechanical linkage is a starter solenoid.
From your post I am guessing you have a switch.
If the switch has 12+ volts when not pushed (on the terminal connected to the battery), and it has none, or much less when the switch is pushed, but the starter spins without engagement, is vital information.
There are several possible answers.

The switch could be bad and not pass enough current to make the starter turn fast enough quick enough to engage.
Use the bare tip of a jumper cable to short out the switch's Big terminal to other Big terminal, (in neutral, with the ignition switch off) If it spins the engine like it should, it is the switch.

The starter could be dragging with the armature touching the field poles causing radical current draw and extreme lowering of the battery voltage making the appearance of a bad switch, but really a bad motor. With a volt meter held on the battery posts (not the clamps) watch the volts when pushing the switch. If the volts drop to less than 10 volts, it could be a bad battery, or a dragging starter. If it drops to less than 8.5 volts it is a under powered battery. Using a starter current meter (cheap at a tool store) check the starter draw if over 500 amps, it is a bad starter. If less than 100 amps, it is a bad battery.

It could be a bad cell in the battery that seems to have a good 12+ volts, but only when not being called upon to deliver 400 amps into the starter. When it is, the bad cell drops to near zero, causing the system to just spin lazily instead of engaging. If the battery is suspect, check the specific gravity of the electrolyte in each cell when fully charged, the SG should be at or above 1.2 (1200) If one is much lower, the bat is toast.

The battery cables could have serious resistance or temporary connectivity that allows pretty good voltage until the starter is engaged, at which time it refuses to carry the amps needed to make the starter engage.
Place the volt meter from end to end on each cable. If the cable is bad it will read more than 1 volt when cranking the starter. If good, it will be less (especially if it is a heavy cable, and it should be OO gauge)

I hope this helps diagnose it.. Keep us informed. JimN

Gary,

Sounds like you are using a test light to trace the power?

Electricity follows the path of least resistance. In this case, that path would be thru the starter instead of your test light. This is normal.

If the starter is spinning and not engaging, you have a mechanical problem with either the starter drive or the engine flywheel.

Ms don't have solenoids. That's another bird entirely.

Alla