My '89 Jetta diesel manual (do people read these things?) says not to pull
the cold start handle until after it starts--it is just a fast idle control
to eliminate the vibrations.  Maybe the Vanagon is different, but the Jetta
cranks slower with the handle out and doesn't  want to start this way.  I
understand the no. 1 cold start problem is crapped up injectors (assuming
your glow plugs are working).  Having the correct oil viscosity helps it to
crank faster.  Block heaters work, but what do you do when your car has to
sit for 8 or 9 hours at work with no 110V to plug in the block heater?

                                                   Jay