Hi guys. Please forgive me if this is an everyday problem, but I'm not a Ford guy (or at least not a post-flathead guy).
I did search the interwebs and this forum and found nothing useful.

I just got my 1980 F-350 manual trans dually flatbed dump last month.
About 118,000 miles, receipt for a Jasper replacement engine from 1995 in the glovebox (along with the complimentary mouse nest).
It hadn't been run in about a year, and I had to reverse engineer the senile, formerly brilliant, elderly PO's pre-mortem attempts to start it in order to get it going.
When it runs, it runs fine, and everything important seems to work (headlights, signals, and wipers each have minds of their own, but I'll get to that when I need to).
For the $300 I paid, I've got no complaints.

My problem is that every now and then, seemingly at random, the starter will jam up solid.
When it does, if I crawl underneath, loosen the two screws, pull it out of the hole a bit, then reinstall it, it works fine again.
Also, when it does, you can turn the crank backward with a wrench, but not forward. After going backward, you can then go forward, but it still won't crank.

Before anyone says anything about electricity, it has a new battery, the alternator charges well, I have taken apart and cleaned all the connections, and all the wires are clean and in good condition.

When it jams, it doesn't turn at all. It doesn't go "Whirrrr—CLUNK!" It just goes "MMK!" No turning, just trying to turn against a hard stop.
Very brief pulses of the starter (five or six one-second bursts) will make the wires and starter noticeably warm, which is to say, it's trying hard.

The flywheel and starter teeth look fine, but I did see a few fine shavings inside the starter nose.

I have not tried to count the flywheel teeth. I did count the teeth on the replacement starter and they were the same as the old starter (sorry, I forget the number).

And finally, I replaced the starter after the first time this happened, but that had no effect.


Does any of this ring a bell?
My next move will be to put a couple of thin metric wave-type lockwashers in to shim it out (about 0.015" to 0.020") and see if that helps (works with GMs. and yes I know that GM starters clamp in radially while Fords clamp in axially, so the effect of shims will be different).

Thanks for whatever you can tell me,

- Eric

 

I think a new one is in order.

 

You mean a new one to replace the new one? Like a new new one?

- Eric

 

New grounds maybe? I replaced all mine and seems to help with a few issues I was having.

 

I'd take it back for exchange.

 

Just one cable from the battery to the block, then it's the block to the starter.

I have seen cases where a starter support bracket provides an essential ground path (late-'60s Oldsmobiles), but that doesn't seem to be the case here.


Fair enough. I certainly could have gotten a bad rebuild from NAPA.

Overall, though, if you've got some experience with these, and you feel that trying a different unit is reasonable, the bottom line is that the problem I'm having is not common enough to have a pat answer, which is to say that I've just got to diagnose it one step at a time using common sense, rather than "Oh, that's always this thing here."

After seeing the responses to this question, I'm reassured that I'm not an idiot because I don't know that "every Ford 351M needs XXXX in order to work right. Duh." (Most makes have a few of these facts, which are only obvious to those who've been working with them for years).

I don't use this truck that much, and winter's coming, so I'll keep at this when I can or need to, and if I find a solution I'll post back in case someone else has the same problem.

Thanks,

- Eric

 

Take the starter back out and look at the starter drive. Make sure the back of it isn't getting slammed into the ring gear. If it is then you probably have a starter with 3/4" throw and you will need to find one with 1/2" throw. For some reason reman starters all end up in the same boxes so telling the parts store guy this will mean nothing to him, just look through what they got till you find one.
I used to think they were all the same till I had trouble changing one and caught that. You can measure the distance from the starter plate to the end of the ring gear to be sure which you need.

 

Now this is valuable information. I had no idea that Ford starters had different throw distances.

Can I assume that if I remove the wedge-shaped cover and press down the metal plate that the starter pulls in, that will throw the gear out the proper distance so that I can measure it?

Thanks,

- Eric