Voltage drop at starter

[Oakr11]

I know this is brought up frequently and I have read through similar threads , but here’s where I’m at if anyone can help.

Truck is new to me and was starting fine until yesterday. I was just test driving it around my neighborhood and it cut off, went to restart it and just a click, tried to jump it and same thing. Grabbed my new XS Power battery out my car and tossed it in this time cranks very slow but no start.

So today I have replaced both ground straps and cleaned connection points, replaced ground cable from the battery to block and battery to fender and cleaned all connection points. Replaces battery cable from battery to starter, battery to alternator, and battery to fuse block. After all that the truck does the exact same thing very slow crank and will not start.

I did have the starter tested this morning but I was not confident in the young lady working at autozone but it did test good, went to Napa for conformation but apparently that location does not due starter testing.

I took a video (not sure how to post it here) of my voltage using a fluke 77 multimeter, I’m at 13v, 12.6v key on and drops to low 8v cranking. Where should I go from here ?

 

[Oakr11]

Do you have an amp meter that can be clamped in the battery cable? I would bet your starter is drawing a ton of amps! If it is then most likely the armature is dragging inside the starter. I would zip it apart and see. If you are pretty resourceful jump on it, if you’re not very mechanical inclined take it to a starter shop and have them pull it apart. It’s pretty easy to get apart not so easy to get the brushes back on the armature.

 

[Schurkey]

Adequate battery voltage with no-load, insufficient battery voltage when cranking is most-likely a failing starter motor. Since you've had this happen with a "new" battery, it's probably not the battery but that is an outside possibility--as is an engine with mechanical problems causing high drag on the rotating assembly.

"I" would either rebuild or replace the starter and see what happens. The older in-line, direct-drive starters are ultra-easy to rebuild. The only tricky parts are getting the lock-ring assembly off of the motor shaft; and getting the old bushings out of the front and rear of the starter assembly. Putting the new bushings IN is not a big deal, neither is putting the lock ring assembly back into place.

But the hot set-up now is to put in a Permanent Magnet Gear Reduction (PMGR) starter motor assembly. See attachment.