94 Explorer wont start after changing Crankshaft position sensor

[NT45]

I changed the crankshaft sensor and now it wont start. It turns over but wont start. It started fine before I changed it. Anybody have an idea what I may have done wrong or what could be causing this?

 

[Number4]

Besides "why did you change it," put the old one back in and see if it starts. Could be a bad sensor.

 

[trashtruck]

number4 is right, verify the sensor is good. it may also be the connector, the icm, the coil pack, the ecm, or related wiring

 

[Jon94]

If the truck started fine before you changed it, then you didn't need to change it in the first place.

You can test the sensor by hooking up a multimeter to it. Connect each of the multimeter leads to the two wires going to the sensor and set the multimeter to V AC. Have someone crank the engine while you look at the multimeter. You should have about 5 V while cranking, and 0V while not cranking.

 

[larrydd999]

Volts AC or Volts DC?

 

[Jon94]

Volts AC.

 

[natenkiki2004]

Just to throw it out there, that will prove that it's not totally shorted but it won't prove that it has a proper waveform like an oscilloscope would. Basically, it proves that it's not totally dead but doesn't prove that it's working perfectly.

 

[Jon94]

I just remembered another easy way to test a crank sensor - this works on Fords; it doesn't necessarily work on other makes - When you turn the ignition on, the check engine light should turn on. (If it doesn't turn on, then either the bulb is burnt out or the computer is not turning on - check the ECM fuse and ECM relay in that case)
As soon as you start cranking the engine over, the check engine light should turn off. If the light stays on while cranking, then the computer is not receiving a signal from the crank sensor.