1988 S-10 Blazer 2.5l - No fuel spray while cranking

I have a 1988 s10 blazer 2.5L that will not cold start most of the time. When it is acting up there will be no fuel spray from the injector while cranking. Also there is no ground pulse at injector at these times. Sometimes after cranking if the key is left in the ON position the engine light will blink eratictly and I hear the injector spray. If I crank it again after this happens it will start and run. If I use starting fluid it will start and run. Replaced parts are; fuel filter, fuel injector and relay, coolant temp sensor, throttle position sensor, O2 sensor, fuel pump, ignition switch, egr valve, battery, starter, alternator, plugs and wires, cap and rotor and air filter. None of these has solved the problem. My next part will be a hall effect switch or computer. Has anyone heard of this problem? Any help would be great. Thanks Brennon.