I have an 87 Blazer. 5.0 litre. What controls the Fuel to the TBI and Spark to the Plugs. Is there a Sensor that controls these functions? I have replaced the ECM, Rotor, Coil, Cap. I also replaced the PROM chip on the ECU. I am still not getting Fuel out of the TBI or Spark to the Plugs. i'd appreciate any help, thanks !