686 diesel starter problems

Chrissub

Member
I have a 686 Diesel that the starter wont engage the flywheel every time. The starter drive turns but it wont engage the flywheel. The starter has been rebuilt with new drive but still the same problem. It takes 4 to 5 tries before it will engage. I painted the gear on the starter so I could check engagement and that measured around .400 which should be fine. Starter has been to 2 different starter rebuild shops and both said the starter and drive are correct. Drive gear has 10 teeth and measures about 1.250" Anyone ever had this problem? I'm open to suggestions. Thanks Chris
 
Little variances in the solenoid and the linkage and fork that slide the pinion gear into mesh with the ring gear can cause this.

Ideally, the solenoid contacts should close and give power to the starter at the same instant that the gears touch, or a split second afterwards, if the solenoid contacts close too soon and the starter pinion is already turning FAST as it hits the ring gear, the teeth may not engage, and will just "grind".

Some starter solenoid linkages have an adjustment for this, others do not, and I have no way of knowing if yours does.

If the starter shop could try different solenoid, or bend/tweak the linkage or fork a bit, it might help, I have done this.

It would be interesting if you could "borrow" a different starter and see if it acts any differently.
 
I have found that the bevel on the starter gear is not correct its to flat on the end of tooth.If it is aligned it works other wise not.
 
My question is if this is original starter or has it been replaced with a rebuilt one at some time
and when did the engagement problems show up. On that model tractor, there are two different end
frames that fit due to two different starters and drives with different amount of teeth used way
back on the 656 tractors.

Rebuilders often get the end frames mixed up as they both fit just fine. Back in the day I ran into
that with a 706 gas as well as a 656 gas tractor.

As far as the taper on the ring gear, years ago they were all tapered with clutch solenoid style
drives but not on bendix style drives. Later, IH didn't taper any of them.
 
I'm working on this tractor for another guy. He has had the tractor for awhile and its always had this problem. I have never ran into this and cannot accept that it cant be corrected. Both starter shops told us that it was the correct starter and neither had any suggestions on how to fix it.
 
Then about the only thing to do is try a different starter that you know works. Impossible to just look at the drive end of the starter to know if it it the correct nose cone.
 
Or one other option, try the 9 tooth drive as that is what was changed. The nine tooth gear uses a different nose cone (drive end housing) than the 10 tooth drive. Been there, done that.
 
Ran into same problem on mine as well.Put in the correct starter(686 with the D312) and it did the same thing your talking about.Those delco style starters will accept
different length solenoids and a lot of different nose cones.I had to use the original nose cone and the longest solenoid that can be mounted on starter to make it work
for me.Like Bob below said using the right solenoid/bendix/nose cone setup makes a difference.Basically the drive gear wasn't traveling far enough to engage ring gear.
Paul
 

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