I have developed a problem with my 85 GL.  It has 195k miles with new head
at 125K and normal maintenance. Lately there are times when I must crank the
engine for 10-15 seconds or more before it will start.  The longer times
seem to be when I try to start it after say a 15 minute shutdown.  Cold, it
usually starts is a second or two of cranking. It runs fine otherwise. My
mechanics worked for a week trying to identify the cause without success.
They did find other things that need fixing.

What I know at this time is:
 
Not the O2 sensor - replaced
Not the fuel pump, filter, pressure regulator - replaced
Not air leaks - replaced intake boot and a few hoses
Not the timing or distributor - check, cleaned and adjusted
Have never replaced the computer or the air flow meter
Stepping on the throttle (air inlet) does not make a difference
On one occasion it stopped at a traffic light and did not start for a good 4
minutes of cranking. 

During the starting phase the engine is either not getting enough air, spark
or gas at the right time.  I don't think it is the spark. 

Do any of you Vanagon wizards have any ideas where to look next? 

Larry