help-sierra 1500 will turn over but won't start

[performance06]

the truck turns over but wont' start, we've checked and replaced the fuel pump and fuel filter. the fuel pump doesn't turn on unless the relay is bypassed but still no gas is getting to the engine. i can't figure out whats wrong. also we switched the relays around and checked them but it didn't help

[2000CAYukon]

What year? Engine?

//2000CAYukon

[performance06]

1990, i think its a 305 v8. 5.0, 5.7L?

[maxwedge]

Originally Posted by performance06

1990, i think its a 305 v8. 5.0, 5.7L?

Ok, you have fuel pressure, right, by bypassing the relay, do you have injector pulse and or/spark, the injectors also have fuses remember if no pulse at the injector plugs. See if it starts with carb cleaner sprayed into the TBI to confirm it is solely a fuel problem, all of this is basic diagnostics.

[2000CAYukon]

Looking at the factory manuals for 90, a bad oil pressure switch can cause the pump to not get power.

//2000CAYukon

[performance06]

Also I tried to use a Snap-On computer to do a diagnostic check and that did not work. It couldn't connect to it or something

[performance06]

So now its running I took my chances and bought a new EMC, threw it in and it started up. Passed air care, got insurance, than a 24hr suspension. ....

[navyordie]

I have a 1982 GMC Sierra, V-8, 305, with a rodchestor quadra jet carborator that has done the same thing. was running fine then all of a sudden wont start. replaced: spark plugs, spark plug wires, coil, modulator, modulator pig tail, distributor cap. mine still wont start. any ideas?

[Sonny01]

navyordie you should start your own post...you will get better responce.