[T2] why won't it start.

[Susanne]

Check your connectors to the ECU, and all the other connectors (and wires into and out of your plugs).
My 78 had a similar problem after pulling and replacing the motor, one of the contacts on the big multipin connector to the computer wasn't making contact (sloppy connector) when we reinstalled it, and it turned out that was keeping the injectors from firing.  It was a PITA to chase down (we tried EVERYTHING) and I put those darned multipin connectors on the "make sure they're all in place and nothing lose before proceeding" checklist for the next time I did that.  

The other thing to check - your cold start injector - it could be either not spewing or constantly spewing - either making cold start difficult or impossible, or flooding the engine immediately.  (My brother's Typ-IV did this.)

I would bet dimes to donuts it's in your injector/fuel system somewhere...  when they work, they work excellent, when not, they are the spawn of the evil one.