I can turn the key over and sometimes check engine light comes on right away and other times it won't. I can hear a distinctive prime sound or click sound and the light will come on. I have resorted to tapping on relay switches in the panel under the hood rather than waiting. I would just start replacing relay switches if I knew that would end all of this. Oh yeah, the check engine light failed during emissions check so I need to get this fixed for good.
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1994 Ford Explorer
Question: Check engine light sometimes doesn't come on. Why doesn't car start without it?
Answer #1modeauto from Mode Automotive Repair, July 09, 2011, 16:03Technician
IF YOUR CHECK LIGHT DOESNT COME ON WHILE CRANKING POSS. ECU POWER RELAY IS BAD, OR BAD ECU. AS FAR AS CHECK ENGINE LIGHT CODES, THOSE WOULD NEED TO BE DIAGNOSED, MOST LIKELY A BAD SENSOR, HOPE THIS WAS HELPFUL.
SINCERELY, RYAN MODE
Answer #2West Escondido Automotive & Transmission (5 Answers) , Escondido, CA - (760) 206-4550West Escondido July 09, 2011, 19:50Enthusiast
Sounds Like a relay that is starting to fail, Recommend getting it diagnosed properly to prevent replacing good componets. Sounds like the vehicle failed functional because the check engine light did not come on when they check to see if it works during the functional parts of the test. Getting the no start relay problem fixed should cure your smog failure for functional propblem