need a definite answer: will a 5.9L cummins starter work in a 7.3L IDI ?

conflicting opinions.
tried a spare cummins, but it never engaged the flywheel.
bolt pattern is same.
nose is different, but looks like the proper gear extension (didn't measure it, already had the ford starter apart)
pics on the web of the gear reduction starters for 7.3L look identical to the cummins.

I would really like to have the gear reduction on the ford.

There are lots of gr starters made for 6.9 7.3...…...all 7.3s came with one.

@Macrobb did it once.


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There are many different "5.9 cummins starters". I had one off of a first gen dodge cummins truck that looked like it would work......if the huge motor would clear. Never tried it, but by all measurements...and correct rotation it should have worked.

79jasper said:

@Macrobb did it once.


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Click to expand...

Yes perhaps... But I think that was a different Cummins starter. I still have that one - brushes failed a year later(was not new when I used it), and it's in a drawer.

I more recently tried one from a 24 valve '99 cummins, and it didn't work. I don't know why - everything lined up, and everything measured. but something prevented it from actually engaging I think.
It was a "bad" starter I'd repaired, though, but tested fine on the bench...
(I ended up stealing the 'motor' section off of it to replace the same thing on my tractor; where it's still doing great). All of these "denso-clone" units are very similar and can be swapped out easily enough - it's just the gear reduction/nose section that differs by application.


That being said, unless you have one handy, just grab one of these: https://www.ebay.com/itm/173473910925
It's literally the /same exact/ starter as the cummins, just rotated differently for the IDI... and being a cheap clone.
But I've used a couple, and they work just great.

You can also use this style too - https://www.ebay.com/itm/130682184399 I don't particularly /like/ them because of the size. Speed is... exactly the same as the other style.
And they are gear reduction as well(I've taken both styles apart).

Thank you.
Near as I can tell, there is a difference in the '95 and up starter noses.
And it looks like those are the same as the 5.9L cummins, which is why it wouldn't engage on my '91.

Maybe someone can correct me if I am wrong.

fsmyth said:

Thank you.
Near as I can tell, there is a difference in the '95 and up starter noses.
And it looks like those are the same as the 5.9L cummins, which is why it wouldn't engage on my '91.

Maybe someone can correct me if I am wrong.

Click to expand...

By '95 and up' I'm guessing you mean 7.3 PSD? If so, it's actually 94.5 and up, but more importantly, the difference is that the nose is 1/2" shorter.
An IDI starter will 'work' on a 7.3 PSD, but it won't disengage - you'd have to add a spacer if you wanted to use one.
Vice versa, obviously not(1/2" too short).

Cummins(at least the 24v 1999 one I have) starters look almost identical to the 7.3 IDI starter of the same design... but something's just a hair off. I could not find a difference holding them side by side.