good pressure at the rail, but injectors don't open!

[gnork6y5]

I have good pressure up to my injectors but they do not open and no fuel gets into my cylinders. The fuel rail is definitely pressurised. What kind of signal opens these injectors? Should I get a voltage reading across the wires leading to the injector while cranking the engine? I get 15.9 ohms readings on each injector. I know I have good pressure with a new filter and main pump. I know the in-tank pump works just fine too. I replaced the computer with one that was said to be good, but I have no idea how to test it. Is there a way to bench test this computer? The car will start for a second with a spray of starting fluid but will not run. We tried disconnecting the mass airflow sensor and still no luck.
Any help would br greatly appreciated

[jetmech]

as I understand it, it depends on which engine/fuel delivery system you have. If you have a single cam, non-turbo, 4 cylinder, with the Bosch LH, in an '89 740, I believe that you have a "B230F" engine. I understand that engine to have a positive feed from the battery to a relay mounted by the coolant tank (radio interference suppression relay) to the injectors, and then controlled ground thru the ECU. The control side of the relay receives power off of the ignition and grounds the body. This could be bad info, but it is the info that I am using as I troubleshoot my own fuel delivery problem. If you can get it running, you should be able to hear the injectors clicking with a mechanic's stethoscope (or suitable sub).