When i turn the key on the throttle body fills up
My truck is a 1987 4cyl and when i turn the key on the throttle body fills up. on 1990 GMC S15
Leaking injector o-ring seals. Most likely! Unplug injector wire connector to see if it still does it. Post the test results for more info.
A defective ignition module was a common cause for this. They would falsely send a very fast pulse on the ref wire to the PCM even without the engine cranking.