I have an old one, a 1995 chevy blazer. It stopped one day and I have been able to get it start since. We changed fuel fliter, spider injector pump, and fuel pump in the tank. I checked to see if fuel relays are working and they are. The pump in the tank is working, while changing the filter we checked and it is. Still no fuel is getting to the engine. What can I try next? Is there some way of checking the ECM to see if it is allowing fuel in? Help!

Have you tested for fuel pressure at the pressure test port, labeled here as FUEL PRESSURE CONNECTION?
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Have you checked for spark at each plug? If it's not sparking, focus on the Ignition Control Module and coil.