Need starter help.

So I have been trying to figure this out but I am unsure what the problem is. I am using what I think is the original starter that was in the 4 runner and I am using the original flexplate.

When I turn the key the starter just grinds occasionally grabbing for a second when you bump it but then start grinding again. Im not holding the key on when it grinds letting off. I have pulled the starter probably 5 times now. The teeth look fine. I turn the motor by hand and it turns. I bench tested the starter and it extends and spins. I can go buy a local autozone starter to test but they won't let me return it after if it's not the problem. I don't know how the wrong starter would be with the 4runner but maybe a manual vs auto starter problem?

 

Since you've bench tested the starter and it works, then the issue may be in the thick electrical wire that goes from the battery to the starter or perhaps the battery contacts are corroded. Clean the battery terminals and check the wire for corrosion. Per my experience if there are any corrosion or failures, they're either in the near proximity of the battery terminal or at the starter contact. How old is the starter? Since it is out, you might as well buy a rebuild kit. It is a fairly easy procedure that is worth doing especially if it is the original starter that you have.

 

I had an old car that the ring gear was missing a few teeth. The starter would throw out its gear and wouldn't be able to grab on to anything to turn over the engine. Sometimes it would work after a few tries. Engine always seemed to stop in the same spot. Had to pull the engine and replace the ring gear at the back of the engine.

 

Have you changed the contacts and plunger in the starter? Essentially a simple and cheap rebuild.

 

I have not rebuilt the starter. I am unsure if it is an oem starter or a reman. It has one sticker that is ruined from oil. I know the starter worked when the truck originally broke down.

I have spun the engine over by hand and tried starting in different spots of the flexplate same result.