Crackshaft damper tach pin rubbing?
 

Hi All
A short while back when I checked my 1985 300td timing chain stretch, I noticed that the pin that sticks up from the damper next to the TDC mark - is polished and showing wear at the end - like it is scraping on something.

I'm guessing that the pin is part of the techometer pickup system but am not sure.

Does anyone have an idea as to what the pin could be scraping on - and what might be needed to correct the situation? Or is it not a problem? My techometer seems to be working fine.

My Haynes manual is no help here and my FSM CDs have quit wanting to load.

All advice appreciated,
Joseph

Seems to me that if it was making contact, it would take only seconds at a few thousand rpm for it to be "machined" to fit.

every one that I have seen appears to have made contact at some point in its life.

Considering that this area is so messy and dirty makes it easy to imagine erosion on a plastic piece like that.

Vibrations in this region are a big factor as well. [pulleys]

The tach system in your '85 does not use that sensor at all, so your tach will be unaffected even if the pin completely destroys the sensor.

The sensor is wired to your "diagnostic plug" inside the left fender. In your car, it is completely unused unless some sort of diagnostic tool is plugged in.

It's a pain to get to, but if I were you I'd simply verify that the sensor bracket is securely attached and there is clearance between the pin and the sensor face.

Hi Bob
Very helpful information!

I spray painted the pin so as to be able to tell if it is still scraping. The leading top edge of the pin does have a bevel - not sure if it has worn that way or not. Everything around the sensor is packed with dirt/grease - very hard to see what's what - I'm working on getting that cleaned up before I crank the engine.

Could you direct me to pics or a diagram of the sensor? How is it held in place and is it adjustable?

Thanks,
Joseph

I don't have a good set of pictures. It the sensor mounts to a small bracket on the front of the engine. The bolts can bee loosened and the bracket can be slightly repositioned. The bracket can also be bent slightly to eliminate interference.

Hi Bob
You were right on! I used a screwdriver to pry up on the sensor bracket and the pin no longer scraps. I have no clue what caused this problem to develop but its now fixed
Thanks,
Joseph