So,
Today I jumped the starter directly from my running other vehicle.
The starter spun freely and immediately.
It did not engage the engine. It did not "pop out" I am guessing. But it did spin just fine.
Should it have engaged the flywheel?
I tried it engine cold and engine hot. It jumped exactly the same both times.

Battery on truck was unhooked.

Extra note: When the truck was hot and hardly turning over. I jumped it normally (via battery) from other running vehicle.
It did not make the starter turn the engine over much more effectively than when not being jumped. Hope that makes sense.

Thanks for your help, guys.

It wont pop out & engage the flywheel unless you also bridge/jump the solenoid.

This is good progress, I would say you may need to replace the starter power cable from the battery to the starter. Also add a earth strap from the starter to the chassis. & check & clean the earth cable on the battery - between the battery & chassis.

As said before, higher temps increase resistance, which will cause current drop & restrict the power supply to the starter.

Hope this makes sense.

ah, right. duh.
so I need to run a jumper from the pos. terminal on starter to the "other" nut that has wire running directly into starter motor?
Then jump it from other vehicle. (Isuzu rodeo)

I should replace the positive cable/wire that runs from starter to batt. ?

Currently there is a NEW ground/earth wire/cable from mount bolt on starter to the batt. I should add a second one?

You've potentially found a issue with the power cable to the starter, get that checked/tested.

k.
will report back soon.
but
to jump starter
jumper from both terminals on starter. Then cable from other vehicle?

Apologies for my slow reporting.

I just haven't had time to do anything on it. Just start it once a week to keep running.

Today I put a jumper on the starter.
Meaning: I put a wire from post to post on starter itself.
It turned the engine over really well. A couple times the starter just spun, but overall turned the engine over just fine.
This is with the battery in the truck. NOT another vehicle.
But
When I tried turning over from the key the engine BARELY turns over.

Soooooooooo….looking at the wiring diagram (thx cusser) trying to decipher what component could be bad in there.
Back to that.....

https://cimg3.ibsrv.net/gimg/www.maz...2d3ca3c38b.jpg
See picture above; lets call the three terminals 9, 12, and 5 o'clock as we look at the photo.
I'm not sure exactly where you "jumped" from battery positive terminal.
(a) If you jumped to 9, starter should spin the engine right then every time if all else is OK
(b) If you jumped to 12, starter should spin the engine every time you turn the key to start position if all else is OK
(c) If you jumped to 5, starter should spin but the engine will not spin if all else is OK
So you need to detail if a, b, or c describes your situation.

Thanks for this.

C) I put a heavy gauge wire from 12 to 5.
The key was not in the ignition or turned on in any way.
It turned the engine over.

hope that clarifies.

Jumping from 12 to 5 and not touching 9 should cause the starter to spin, but the starter gear "should not push out to engage with flywheel and then cause the entire engine to spin".

Try jumping from 12 to 9, should cause the entire engine to spin. If not, test electrical portion of ignition switch, the wire to the 9 o'clock position, and either the clutch safety switch or neutral safety switch, depending on your transmission type.

https://cimg3.ibsrv.net/gimg/www.maz...e00c8a95f5.jpg
K.
So "jumped" 12 o'clock to/with 9 o'clock. Turned engine over no problem. no hesitation.

Tested the clutch switch (plastic one). Am I testing for resistance? Because there is no current.
Got .6 resistance.

Also, I took apart and cleaned it. was some grime in it.