Hello,
I have a d6 9u that I bought at an auction the owner said he was having issues with the pony motor and it was parked for 3 years. I found the issue with the pony motor and got it running. I went to engage the diesel engine and had it turning over but forgot to give some fuel to it. I shut the pony motor off to investigate, then realizing my rookie mistake (my first old dozer) I went to try again and never could get the pony to engage the diesel engine. Now the diesel engine seems to be locked up. I can not turn it over by hand using a pry bar and the gears on the front of the engine. I also noticed that the rod that attaches to the rear lever looks like it melted off or had been rubbing on something that blued it. My question is: is there anything in the pony pinion that could fail and cause the engine to lock up or should I pull the head and see if the cylinders have rust in them from it sitting for 3 years. It seemed to turn over fine when I tried the first time. Thanks for any help you can provide. I added a pic of the engagement lever I mention

If the main is locked it may have had water in a cylinder and and the rust will not allow the piston to move in the cylinder. If you are trying to turn the main, make sure you are trying to turn it backwards to get it away from the rusty cylinder wall that probably has a rusty ring where the water sat. To turn it backwards make certain the clutch for the pinion is disengaged and the compression relief is operable and relieving the compression. If you can get it turned back a ways and it sticks again, it is probably a rusty cylinder. If the main checks out OK, we can figure out the pony. Disengaging the pinion clutch takes the pony out of the equation if the clutch is operating normal. Good luck.

If the main started to turn and then locked up from a rusty cylinder it may take a good amount of force to turn the main backwards. See if that tells us the problem and it may take some Kroil or similar into the cylinder to loosen the rust. Keep us posted but I wouldn't jerk the head on the pony just yet from what you've described.

If you've had the main and pony turning over than it's not likely a rust or cylinder problem.
I see where the button end that is normally attached to the pinion engagement sleeve has become welded to the engagement lever, probably from long term abuse of holding engagement with the lever instead of utilizing the engagement latches when the latches are not holding. Did you have the pony clutch disengaged and decompression lever in decompression position when trying to turn over the main engine? I suspect the pinion is engaged and you will either need to start the pony with the clutch lever disengaged or manually trip the latches and repeat the starting process.

Was there even any oil in the clutch and pinion housing??? Most likely tide up the bearings and now it wont turn.

does the pony turn at all? when my dozer locked up and it had broken teeth of the magneto gear on the pony. the starting pinion lever is a over centre type mechanism you should feel it pull in and lock then there should be no weight on it afterwards.
the start clutch lever is similar when fully engaged it should lock in until the main fires. if the pinion lever is still weighted the pinion should be disengaged and the main should turn independent to the pony. if engaged you will need to disengage it so you can check them separately.

Hi,
starting sequence for your D6 is similar to this D2/4 video.



Also pinion repair is on one of Toby's videos--should show up down the side suggestion list, D6 pinion and clutch etc. is similar size and layout to D2/4 so this video explains the overhaul sequence and I think explains how to manually unlatch the geared together latches by pushing on the adjustment screw end of one latch.





You should also be able to find video by Toby on pinion latch adjustment and linkage issues --yours has been abused as said above because the pinion latches unlatched too early or are excessively worn on the latch shoulder and/or the stop bolt head.
Hope these helps as it saves a lot of writing.
Cheers,
Eddie B.

The pony and main engine was turning fine until we shut the pony down then the main engine would not turn anymore. The pony will still fire up and run. We just can't get it to engage or the main engine to turn by hand. We even tried to soak it in atf and diesel for 2 weeks and tried to pull it in high gear to get the main to turn over. I took all the injectors out and the cylinders looked clean except for one has some rust showing towards the top of the cylinder. I was going to pull the main engine head to get a better look than just looking through the injector hole.

We tried the pony clutch engagement both ways and with the pony running it doesn't bog down when you move the clutch lever how do you manually disengage the pinion?

The old man said he didn't even know there was an oil place there (when I asked him about it) but the pony starts and runs still

You mention the main was turning over at one time. Did it turn over multiple times or did it just rotate a ways and stop? IE Are you certain the main was rotating complete revolutions?