hello and welcome,

recently another forum member had a similar problem, turns out his no-start problem was caused by a combination of cold temperatures and water in the fuel tank. here's the link:
M104 will not start you may want to rule that out first.

i believe that the M104's from 1993 on, with HFM engine management, do not have a cold start fuel injector.

The majority of M104's had 2 major problems: 1) head gasket(poorly designed) 2) wiring harness(biodegradable wire insulation).

If both have already been replaced then you're in luck, the no-start problem is probably something simple like : 1)faulty ECT sensor(important for cold starts), 2) old/wrong spark plugs, 3) faulty under coil connectors, 4) fuel pump relay, or 5)major vacuum leak(s).


you should also build a code reader which will allow you to pull the Diagnostic Trouble Codes from the engine's computer. Check out the following thread which explains how to build it, specifically post#11: Reading Codes

PS i believe that the numbers in the diagram are Radio Shack part numbers, should make obtaining the proper parts easy.


good luck