I just went through a hellish month or trying to start my 89 740. I got lots of help and suggestions from other posters, but in the end, it turned out to be a shorted wire running between the ignition control unit and the engine control unit. So check to see if your injectors are pulsing. If not, then you might have a similar problem to mine. Also, I can list the voltages you should beseeing at every output to the ICU. The wire running between the modules that sends the pulse comes out of pin 17 on the ICU and goes to pin 1 on the ECU. The voltage between pin 17 ICU and grnd should be 0.7V. More importantly, check it to grnd using an ohmmeter to see if it's shorted to gnd (0-ohms to grnd) Let me know how it goes and I'll try to help. Here's a link to the thread on my car.

http://brickboard.com/RWD/index.htm?id=918069

Best of luck!
Don