I think you're retarded....
The timing I mean. When you start up the engine cold, there is a timing advance solenoid that operates to advance the timing. You state that it does not smoke until the engine warms up. Also if the timing is retarded, you will not get a complete fuel burn so there is liquid fuel left to get by the rings. Don't look at piston rings as a seal, but as a permeable barrier that slows things down.
There is a timing retard arm on the drivers side of the injector pump. Work the throttle linkage by hand, and watch the retard arm. It should move in and out at the bottom a good 1/2 to 9/16" or more. When I bought one of my vans this arm was stuck IN which caused the timing to be retarded at low speeds.
If the arm checks out OK I would run a jumper wire to the advance solenoid and see if that helps the smoke.
http://photos.thedieselstop.com/show...amp;thecat=998 If that does help, I would mark the present IP position (so you can return it if needed) and advance the timing slightly. A little rotation does a lot on these.
To advance timing turn the IP to the passenger side. You will need to make a special wrench to access the 3 IP bolts. You need a 9/16 wrench which you will grind both the sides and outside of the box end. Just grind and test fit, you will get it. You have to take quite a bit of metal off. BTW, Sears sells a generic brand of wrenches individually which is what I used.
