Is there ANY way to remove the tach sensor on a w123 without removing the vacuum pump? I pulled a sensor at the junkyard, so removing the vac pump wasn't a really big deal (most of the parts between the vacuum pump and the front of the car were completely gone). I would really love to be able to replace my sensor without removing that pump. How!? An 8mm box wrench doesn't have enough room to grab AND turn the small nut, and any socket I've tried winds up being too tall thereby causing the vacuum pump to interfere with the ratchet attaching.

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

how do you know the crank sensor is bad? Most of the time its the amp thats bad.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Yep that one is a nightmare...

My sensor is not giving any resistance readings off the pins... so it's likely shorted out somewhere.

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

I have exactly the same problem. I've replaced the AMP multiple times; it isn't that. I've even replaced the Tach. I bought the replacement sensor and cable months ago but have yet to determine how to remove the old one without taking the front of the car off! The tachometer is the last remaining element of the car that still doesn't work; I have gone from nothing working (except the engine turning over) to everything working EXCEPT the @%!#& tach! This has been incredibly frustrating. If anyone has a clue, fill us in because I need to know too...
Thanks,
Simon

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Simon Shearer

1986 420SEL

2000 Porsche 911 Millenium Edition Carrera 4
2010 Lexus RX 350
2002 Kia Rio
2002 Hyundai Accent

It's actually pretty easy to remove with the vacuum pump off, but who wants to do that!? There's ALWAYS a good chance of stripping to dang little allen screws that hold the pump on.

There MUST be a way!

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

I figured at the very least there's some $60 MB shop tool that can do the job!

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

remove the very large bolt that appears to hold the sensor's bracket... remove the bracket and you will have access to the sensor.

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I'm gonna have another look at it in a few minutes... I'll let you know if that works out.

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

Yours might be covered in oil/ dirt, so here's a pic with a slightly different bracket. Is the bolt higher up and closer to the pump, it is very shallow and acts more like a cover than a bolt.

79mercy made an excellent suggestion, p.s.

Attached Thumbnails

 

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Over time the wire coming from flywheel sensor gets dry and hard.The engineers should have allowed more slack in this wire.It runs up into the socket for the pins.When you try and screw on amp,the wire slips down.
My solution was to remove screws in socket,pull the wire out of socket holder.Clean everything good,and super glue gel the wire into socket.
Problem solved.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

we are not talking about the flywheel sensor. Earlier models used the crank position as the tach. I don't know when the SD stopped using the crank.

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I'm nearly 100% positive my issue is the sensor. I tried several different amps from the pick-a-part and Bob Myers' tach testing unit. After all this, I determined that my sensor didn't show correct resistance upon connecting a meter to the sensor terminals. The new sensor, on the other hand, does show proper resistance. I'm hoping my calculations are correct and the PITA of removing and installing that little bugger is worth it!

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

did you get the bracket off?

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Not yet. Spent a little while fixing all of my vacuum locks instead.

If I decide not to brave the heat again this afternoon, I'll do it in the morning. I've been waking up at 5 everyday and working on the car for an hour or so. Fun stuff....

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09