wire/cable under vac pump 85 300td

[connerm]

1985 300td 250,000 mi. Removed the vac pump yesterday as I'm barely getting vac at the booster. Dirtiest I have ever been from any auto repair in my life. Check valve is hollow, so I guess the parts puked into the pump cylinder. Anyway, I have the repair kit from Phil, the gasket from the dealer and the new check valve on the way from Phil. Back to the topic...the bottom bolt holding the pump to the block was a pain to remove with my hex socket - it wasn't long enough. There was also a wire/cable in the way. Ran just below the bottom bolt. It attaches to a metal bracket but I can't figure out what it does or is. It looked like it dead ended on the bracket. Any ideas? Sorry about the vague description.

[westkill]

i believe the wire you are talking about is yout tach pickup. it sits in a bracket above the harmonic balancer. As the engine rotates there is a magnet on the balancer that slides past the pickup and signals the revolution and then transmits it to the tach amplifier and then by a miracle of god, the dash gauge moves. HTH mike

[connerm]

Very interesting. Thanks.

[KCM]

On the 1985, that sensor does not operate the tach. The tach runs off a rear sensor that reads off the flywheel. On that year, the front sensor just runs up to the diagnostic socket and is used to hook up a test tachometer for repair purposes.

[toomany MBZ]

Originally Posted by KCM

On the 1985, that sensor does not operate the tach. The tach runs off a rear sensor that reads off the flywheel. On that year, the front sensor just runs up to the diagnostic socket and is used to hook up a test tachometer for repair purposes.

Agreed, on '84's too.