1999 Chrysler 300 Repair Question
300m. can a faulty crank sensor cause the pcm to not send voltage to injectors and coils?
scan for codes and check fuel pressure first. if you think it's the crank sensor check connections.
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My friend replaced the fuel pump thinking that was the problem and still crank but no start. Unhooked the cam sensor and no start. I Would really like to know about testing the crank sensor. I've heard about the tach bouncing when cranking if the crank sensor is ok. true/false?
Going to get back to the car for more testing later today.
No codes were found, but will scan again.
3 questions asked
check to see if lcranksensor or cam sensor are getting power and then check resistance of crank andcam sensor, we don't have any specs for there, if the reisitance is high then it may be bad . you'll have to check against a new one unfortunately.
18,721 answers provided
Hi guys. You have to check for voltage to the coil(s) and injectors while cranking the engine. If you do have 12 volts, the cam and crank sensors are working. The bouncing tach is not valid. It is run by the instrument cluster which is a computer module, when it gets information from the Body Computer.
Unplugging either sensor will guarantee a no-start condition. Both signals are needed for the Engine Computer to know the engine is rotating, (cranking or running), then it turns on the automatic shutdown (ASD) relay which sends current to the coils, injectors, alternator field, and fuel pump or pump relay. That's a safety feature to prevent a fire in the event of a crash that ruptures a fuel line. With fuel spilling onto the ground there can be no pressure so the engine will stall, the signals stop, the computer turns off the ASD relay, and the fuel pump turns off. Most people jump on the dead fuel pump but you rightly noticed the spark is missing too.
Hmac300 suggested checking for codes. That is always the place to start but if you disconnected the battery any codes will be erased. Cam and crank codes often will not set during cranking. One of the sensors has to fail while driving.
The best way to tell if the cam and crank sensors are working is to use a scanner to view live data during cranking. They will be listed with "no" or "present". The crankshaft position sensor has the higher failure rate, and both of them often fail by becoming heat-sensitive. The most common complaint is a no-start after the car is parked for 20 minutes with a hot engine. The heat migrates up to the sensor, then it works again after cooling down for an hour or so.
I don't know which style of crank sensor is used in your engine because you didn't list the size, but some of them are adjustable. They use a thick paper spacer stuck to the end to set the critical air gap. If you pull it out, you need to use a new spacer from the dealer when putting it back in. Some aftermarket replacements have a thin plastic rib molded onto the end to set the gap. When reinstalling one of those you are to cut the remaining part of the rib off and use a paper spacer.
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