David, I need just a little more background on this situation before I can
help.
Has this motor been in the van for all this time and just now started to have
this problem or is this a new motor that you just installed?  Or did the
problem start after you just did the head gasket or timing belt on this
motor?

The situation sounds like a timing problem to me.  Like maybe you are 180
degrees out on your timing or you are off a tooth on the cam belt timing.
There was a recent post about someone with a Tiico conversion that had a
loose timing belt that jumped time and then they couldn't get it to start.
Double check your timing.  Pull the spark plug on number one cylinder, put
the tip of a flathead screwdriver down in the hole, and then check to be sure
that when the cylinder is actually on TDC (screwdriver being pushed as far as
it will go out of the hole) that your timing marks are all on the money.

Thanks,
Ken Wilford
John 3:16
http://www.vanagain.com
Phone: (856)-327-4936
Fax: (856)-327-2242