Problem:
89 740GL 4cyl. 8 valve won't start. Sounds like it isn't getting fuel. The engine just cranks but won't fire.
I checked the fuel pressure at the fuel rail and it is normal. If I spray starting fluid in the air intake the engine
will fire and burn it but not start so the ignition system is working. I suspect the injectors aren't pulsing.
How do I check if they are working and if they're not what could be the cause?

 

fuel pump relay or the silent late for work killer... "radio suppression relay" (under hood near PS fluid tank)

 

Agreed.
The Black Relay could also be mounted at the coolant bottle.

 

OK,
I took off the radio suppression relay and had it checked by a elec. technician I work with. He swears it is working ok.
I still think the injectors aren't pulsing. I can't here them when I have someone crank the engine. Where does the relay get its power from?

 

Both the Black and white fuel pump relay controls the injectors.