Got a strange problem with my starter

[nelstomlinson]

When the engine is room temperature the starter will crank the engine quickly for a couple rotations, then it slows way down, have to crank 15++ seconds to get it to start. When the engine is warm, it starts before the starter slows down.

The cheapie digital voltage gauge I have stuck in the cigarette lighter tells me the voltage is almost 12V while it's cranking fast, but drops to ~9V when it slows.

My first thought is the ancient starter has some kind of problem that only bites after a few revolutions. Any ideas what might be going on?

Should have added, it's the '91 plow truck.

 

[Nero]

Dropping to 9v when cranking isn't abnormal. I would get your batteries load tested. 12.6v does not mean a battery is maintaining full capacity. Also wouldn't hurt to make sure the major grounds are clean.

 

[nelstomlinson]

Batteries are a bit over a year old, NAPA's best.

The starter on that truck is the longest I've ever seen on one of these old rigs. I'm guessing it's pretty old. I guess it could be battery cables, too, or could be both.

 

[nelstomlinson]

I took the starter out to change the block heater. It was so long I barely had room to get it out. Now I'm thinking I should have put in a newer starter while I was in there.

Oh, well, it'll get its turn in the shop again next weekend, and I'll definitely check the grounds.

I guess I can cut back the insulation around the battery cables for an inch or so, and if they look good I can cover them again with heat shrink.

 

[IDIBRONCO]

I took the starter out to change the block heater. It was so long I barely had room to get it out.

That's the long style Mitsubishi starter.

My first thought is the ancient starter has some kind of problem that only bites after a few revolutions. Any ideas what might be going on?

This is my first thought as well. The starter works "better" when the engine is warm because a cold engine is harder to turn over so the starter has to work work more for a longer period of time. I would think about replacing the starter soon. After you check your cables though. That's never a bad idea.

 

[Old Goat]

There could be cracks in the full length of the cable insulation.
Moisture/Salt can get into the copper and you have corrosion you do not see.
I noticed one day both of my ground cables had cracks on both of them the full
length.
Measure the length of both and went to NAPA and had 2 new cables made with
Copper ring terminals crimped on. Also replaced the Positive cables as well.


Goat