Weird things that happen in old trucks: Crank Sensor Glitching (1 Viewer)

[elripster]

For quite a while I have been having intermittent stumbling / stalling and sometimes hesitations in my '94. Often after a stall I would restart like nothing happened. The CEL would flicker after some starts and then go out. At one point I thought it was bad gas as the problem would sometimes go away for weeks or more. It finally started to get bad enough to create real drivability issues. The CEL was code 12, crank pos sensor. I looked around the harness / engine bay and distributor connector and nothing seemed awry. I removed the distributor cap and noticed something odd.

That gear is not a gear but a tone ring for the crank position sensor. It should never touch anything and there should not be the darkened band around it.

I decided to get in there with my trusty cell phone and take a close up (after removing the distributor). Would you look at that, the sensor seems to be coming apart or something and is rubbing on the tone ring. Note that this is an A Cardone unit I bought from RockAuto in 2022 when I was troubleshooting a mess of issues, long story... The sensor mounting screws were all quite tight.

For comparison, this is the original 250k mile distributor that I kept, and reinstalled, which is working just fine.

As you can see, the gap is symmetrical and the sensor is not touching the tone ring.

Anyway, if someone, someday, starts getting random code 12's, here is one more thing to check.

Frank

 

[Kernal]

Seems like it was assembled incorrectly when rebuilt by Cardone. FWIW there is a specified air gap in the FSM

 

[elripster]

Seems like it was assembled incorrectly when rebuilt by Cardone. FWI there is a specified air gap in the FSM

Agreed. In this case, the sensor did not appear to move, just a part within it. Very odd. With no time to tear into for the sake of science I gave it a proper burial to ensure it could plague no other trucks.

Frank

 

[Batameez]

A1 Cardone never fails to be A1 trash.