Subject: Engine turns over but will not start
Donald ask: I have an 89 Chevy S-10 with a 4.3 V6. I am having a problem with it running without the vacuum line hooked up to the map sensor but when I hook up the vacuum line to the map sensor it will turn over and attempt to start but will not run. Might you have any ideas what could be causing this and is there anything that I should be looking for?
Donald, this explains what the MAP does… I found this info online:
The Manifold Absolute Pressure (MAP) sensor, senses the air pressure inside the intake manifold. The intake manifold pressure is converted into a voltage signal that’s transmitted to the engine’s computer which then determines how much fuel the engine needs. Under low vacuum conditions (WOT, wide open throttle (suddenly opened) the MAP is higher, the MAP output voltage is higher, and the injectors are held open for longer to inject more fuel into the cylinders. Under high vacuum conditions (throttle closed, deceleration), the reverse applies.
It sounds to me like your MAP sensor is faulty and not delivering the signal to the injectors as needed. I would start with the replacement of the MAP sensor AFTER you make sure there are no trouble codes.
Good luck…
Dave
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