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Posted by hemimech [71.10.56.36] on Monday, November 30, 2009 at 23:38:01 :
In Reply to: 2004 Ram Hemi sometimes doesn't want to start... posted by Jill in IL [208.252.188.161] on Monday, November 30, 2009 at 16:11:32 :
On late model Chrysler vehicles air flow is calculated biased on speed density using engine speed, manifold pressure and air temperature. If the IAT is sending a crazy value to the controller fuel delivery can be inadequate or excessive. Take a look at the wiring to the IAT sensor. The ground side is Dark Blue w/ Dark Green tracer that is shared with all of the other sensors. Most likely this leg of the circuit is good or you would probably have other faults. The side to really look over good is the signal (sensor return) wire Dark Blue w/ Light Green tracer. If this wire has grounded out or intermittently grounds out the signal will max out and the controller will be attempting to start the engine at near 150F ambient. Needless to say not nearly enough fuel will be delivered to start if it’s really 30F out. When checking this wire with the ign. on anything above 5volts B+ indicates it has shorted to a 12volt B+ & anything less than 1 volt indicates it has grounded out on something. When traced back to the powertrain control module it enters on the second connector (Orange when unplugged) in pin location #30(marked inside the module side of the connector numbered left to right from the top down). Also to consider is the most common things I have seen with the 5.7L’s are crankshaft position sensor (Rh side of block near the bell housing above/behind the starter) and dirty throttle bodies, gunk causes blade to lightly stick and also decreases the airflow around the throttle blade (hold the blade open and clean with carb. cleaner).
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