CPS Test

87 Wagoneer Limited 4.0L AW4

Will not crank over, although it did the other day, but would not start.

My wire from the CPS is burnt. can I cut out the burnt section and splice together?

What is the test to confirm the CPS is operating properly?

I will be checking relays and signal from the starter solenoid shortly.

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A while back I rebuilt the NSS and it passes the continuity test, but I am not getting the car to crank. Found the burnt wires from the CPS and think maybe something fried in the computer.( ? )


Fuel pump runs for 3 sec. - all lights and other items work fine - batt voltage is good -

Thanks,

Dave.

Cranking the motor: first, lets A**ume that the battery and main cables are up to snuff. Ok, that leaves us the key, key lock cylinder, remote rod, ignition switch, starter relay, NSS, starter-solenoid, and the wiring between them. When the key is turned to START, the remote rod moves the ignition switch, power is sent to the starter relay--Ok, if the NSS is screwed up the starter relay won't pass power to the solenoid on the starter. The NSS controls the ground to the starter relay. Without the ground the relay won't energize and power doesn't flow and the engine won't crank.

You can test the battery, main cables, and starter-solenoid quite easily. At the starter, simply jump positive from the large lug where the battery main cable attached to the solenoid where the wire from the starter relay attaches. Do this with the key OFF, transmission in PARK, parking brake ON. If the engine cranks that means the battery is good, the cables are good, and the starter-solenoid are good. If that is true, then go back to the key and work your way towards the starter relay from there.

The CPS/CKP crank sensor has ZERO to do with cranking. Without it operating correctly--it generates and sends signals to the ECU--the engine will not START. It will crank with a bad crank sensor, but it won't START. So, you do need to fix the wiring for the crank sensor, but don't expect that to fix a no crank issue.

You will know the crank sensor is working properly when, after fixing the no crank problem, the engine cranks and you have spark to the plugs. Without the crank sensor the ECU will not fire the ICM/coil, and there will be no spark. If, after you have the engine cranking, and at that time there is no spark, then the next logical item is the crank sensor, and you can test its resistance to see if it is good. Now, the crank sensor can be good, but if the wires to the ECU are bad, well, no spark.

Good luck.

Awesome. !!

Thanks Joe.

It was a bad ground wire from the starter solenoid. I have jumpers at the bad wires for the CPS as well as the ground but all is good now as I was able to get it out of the gutter and up in my driveway to finish up.

Dave.

Starter Relay........not solenoid.

D