starting pinion on D2-do I need to release after starting the diesel?

On the clutch lever if you pull it back it engages a brake to stop the pinion from grinding. Then you can engage it. You can do it the other way where you engage the pinion prior to starting. Other guys do it that way. As far as the disengagement of the pinion, that is done automatically when the engine starts.
As far as the "Throttle" you can leave it closed while you are warming up the cylinders because you do NOT want fuel in the cylinders prior to combustion as it washes the crankcase oil off from the cylinder walls. When the engine is warm enough to fire, then open the throttle prior to flipping the decompression lever to run.

I can't recall if you have manuals or not-Operations, Parts and Servicemen's Reference. At any rate, take a look at this link. Billy- did an exceptional job outlining the procedure found in the manual. It took me a while to dig it up.

You have to brake that starting engine clutch to engage the pinion by pulling it to the rear of the machine. I am not sure if you can see the pinion on the D2 while starting, but if braked properly it will stop turning. Release the brake just a bit and maybe more than once and rebrake to get the gears to mesh while the starting engine is running.

Good Luck! By the way...find a source for those manuals.👍

http://www.antiquecaterpillar.net/ACF_v2/showthread.php?t=15844&highlight=starting

Just to point out a misconception that may be cleared up in the threads that are linked above.........I haven't read through them.

When you get the main engine turning over, apply the compression and let the pony turn it under compression...........makes the diesel heat up from the heat of compression and also makes the pony work a lot harder, so that heats things up faster too. Only reason to throw compression on just at the last is if your pony won't run well enough for more than a few seconds of turning it under compression. Then you can probably get started by warming it up longer, opening the throttle and throw the compression on and hope it hits before the pony dies out.

When I think it's probably hot enough to go, I go ahead and open the throttle above half way or so so it starts cleanly and takes on off instead of barely having enough fuel to run fast enough to disengage the pony pinion. If it doesn't start right away, close the throttle again and let it warm up some more. If the pinion kicks out before the main engine starts, decompress main engine, brake and re-engage pinion, engage pinion clutch, put decompression lever back in and let it warm up a bit longer.

Also, you cannot release the pinion once it's latched in without opening up the inspection/adjustment cover and tripping the latches.

I was speed writing during a break at work last night and rereading it CC is right on heating the cylinders. My pony runs really well to the point of using the jacket water and exhaust flowing over the intake manifold. This is generally the time period where you are checking for oil pressure and fuel pressure to build. It will generally start the main engine but not when its cold outside. Then I do leave the fuel off and run on compression to heat the cylinders more while cleaning up the snow around the tractor or whatever I need to do prior to starting. My technique is a little different because the D2 I grew up on didn't have the pony exhaust flowing over the intake manifold, consequently we ran the pony longer to heat the main engine via the water jacket.