Ok, well personally to me it sounds like you have an air leak, when you crank the air being drawn in should move the flap in order to fuel into the cylinders. Does it idle by itself once you get it running? Im guessing not?

Bosch KE Jetronic IMO is the biggest pile of wank on the planet, too many things that can cause u problems, even things like not havin the dipstick in properly will cause it to run badly. On the early metering heads you can't even adjust the mixture properly because you create an air leak removing the screw to get in and adjust it. I've removed breather system on mine to eliminate the whole engine as a potential air leak.

Have you got a boost/vacuum gauge?