Got a 1991 s10 Blazer with a 4.3. Engine turns over but won't start. Fuel pump & sender is good. Tested out relay and it is good. Starts & runs fine when I jump power from a 12 volt constant to the fuel pump at the relay. Getting no power at all to the relay from ECM. Horn, lighter, coolant temp gauge & radio don't work either. Horn/Dm fuse blows as soon as I replace it. Oil pressure sensor & gauge good but that should have nothing to do with it.
I am stumped ! Any assistance would be greatly appreciated. Thanks

 

Have you tested the ecm?

Check for any other blown fuses.