I have a 90 Caprice 5.0 liter engine that won't start. The fuel pump and fuel filter are new and working but something is apparently preventing the fuel flow through the injectors. The ECM Flash codes keep repeating "12" ad infinitum. What does this mean?

 

I think thats normal with it not running, however in your case it might be your problem
OBD-1 Diagnostic Trouble Codes

 

DTC - 12 No distributor reference pulse (diagnostic test active)

First , check all the wiring and all the connectors ( to see if they are pluged in good and have no corrosion ) .

God bless
Wyr

 

is the ignition control module involved in sending a signal back to the Engine Control Module to open the fuel injectors? The spark plugs all seem to be firing ok as the distributor turns. Wires all seem to be ok.