Help identifying diesel tachometer req'd - want to fit it to my car! - Page 3 - PeachParts Mercedes-Benz Forum

Stretch · #31 12-08-2012, 02:37 AM

Hi Jan,

The European non turbo 300Ds (or 240Ds etc) didn't have tachometers. So you won't see much official information about them.

If you look in the FSM you might get some joy for the turbo chassis numbers (for example 123.133 or 123.190 - don't bother looking at too much stuff past about 1983 because they started to put in "computers" <= I use the term very loosely!)

The plug on the end of the sensor does indeed go to the amp and the amp then has a plug that goes to the gauge and then there's got to be some sort of modification to give it power (which some people take from / tap off from the glow plug supply).

Please note:- I still haven't finished this project yet. The car is still in bits (and might get scrapped if things don't improve here).

Oh I've just had a thought. There's a Dutch forum member who had a tachometer on his W123 200D (for his privacy please send me a PM if you want his name!) that used a bit of wizardry to take a signal from the alternator. Apparently these were for sale on ebay at one time.

dude99 · #32 12-08-2012, 02:42 AM

This may be of help to this thread:
Installing a tach in a w126 diesel

cornemuse · #33 12-08-2012, 10:55 AM

For what its worth:
I had the motor out of my (diesel 6.2) Blazer and while out I made a bracket (using a water pump bolt) to mount the sensor (123 from Ecology wreckers) at harmonic balancer before re-installing engine. Mounted amp (same place as MB!), Works perfectly!! On power from glow plug relay, clock power from batt with fuse. Its not @ tdc, I didnt want to modify the timing probe holder on the 6.2. -corne-

Govert · #34 12-08-2012, 04:50 PM

The 200D, 240D and N/A 300D had a bracket to install the pickup on the crankshaft. If you wanted a tachometer, you could install one, but you had to buy all the parts: tachometer pick-up, diagnostic plug, tach amp, wires, brackets. The power for the tachometer doesn’t come from the glow plugs, but from fuse 12.

The turbodiesels without a tachometer always had the pickup on the crankshaft and the diagnostic plug. If you wanted a tachometer, you had to buy a tach amp and a tachometer and the wires/plugs.

For the USA this system was used until MY 1983. After that year the tachometer used a signal from the flywheel and from the EGR computer. The tachometer was different, because the signal is different. The EGR system also used the signal for controlling the EGR.

In Europe no EGR was used, so the crankshaft sensor system was used until 1985, but not many people installed tachometers on their diesels.

There is no problem to install a pre-1984 tachometer in a 1984-1985 USA W123 diesel, but you need the tach amp and some different wiring.

I had a 200D with a tachometer which took the signal from the alternator. I bought it from ebay from a seller who could convert a tachometer for alternator use. You needed to make a W terminal on the alternator, but that is not that difficult.

There might have been mechanical tachometers, which were driven from the oil pump drive, but I’m not sure.

So there are:

- crankshaft tachometer, on the back it says 6000 Imp
- flywheel tachometer, on the back it says 14000 Hz
- alternator tachometer, aftermarket, no indication, rare

Stretch · #35 12-09-2012, 01:43 PM

Quote:

Originally Posted by Govert

...

There might have been mechanical tachometers, which were driven from the oil pump drive, but I’m not sure.

...

I get the feeling that they are meant for diagnostics only - something a mechanic would fit during a service but you wouldn't drive around with it fitted.

degier · #36 12-12-2012, 08:02 PM

Nice, the resuscitation of the thread worked.

Wow what a forest still...
Wonder what type my tach is. I will check if there´s a bracket of some sort near the crankshaft.

I have a 1986 W123 turbodiesel here which will be the donor for my current car. Nice motor. so before spending lotsa time n dimes to make it all work on the NA 300D, I will check out the stuff presented by Govert.

Thanks!

J.

Ps:

The idea for a tacho really came from changing the differential on my 300TD. It had a 3.92 diff under it and was kinda hysterical to drive over 90kms/hr since here in Norway they as a standard put 195 70 14 tires ( or 195 65 15) under this car. Changing to a 3.69 from a donor 300TD I found helped some, but still not good. The speedo was also way out. Now I redid the whole front end and rear subframe and used the 3.07 diff from the 300TDT. Kinda cool, never had a car where the speedo was spot on!

The tires on the papers following the car are 185 HR 15, meaning 185 82 15 ( =100kg extra load-type rear axle). So you´re guessing right that it´s become all a game of juggling with numbers between diff, gearbox, tire sizes and rpms within the torque band. Fun yeah, but a tacho would really help sorting this out. Especially when the 617 turbo is moving in, so I can benefit from the boost from 2400 rpms, pulling trailers op these hills.

For more anal analizing; I really like the dead on speedo now and the rpms are certainly allright. The big BUT is, sure enough...there is one, I want more clearance under the car and therefor preferably have the high tires in place again. Gives me a full 2.5 cm( 1 inch) extra. With these dubious backroads in honkytonk Norway my oilpan quit being happy. Someone having a spare skid-plate?? (or a G wagon for that matter lol...)

learning...learning..

Stretch · #37 12-13-2012, 03:47 AM

Skid plate? Did I hear skid plate?

Have a look here

Heads up cheap dealer part - W123 skid pan / skid plate

If you are quick there might be some left - and they're quite cheap (for the dealer) - don't bother with the rubber bushings they come with the skid plate anyway (and if your's don't I'll send you my extra set if I can find them!)

Nice information about the differential. I was wondering if a 3.07 would help. In the end the 300DTs were fitted with a 2.88 (just in case you're interested).

For ride height =>

Mercedes actually fitted taller springs (and possibly spacers) with 15 inch wheels for countries with crappy road surfaces. Have a look at the FSM chapter 32-010 for all of the variations on the theme. The part numbers are listed but I'd be surprised if they are still available.

Here in Holland they sell taxi springs "taxiveren". This guy is usually a good bloke to get in touch with

Mercedes onderdelen voor iedereen | www.SterOnderdelen.nl

I asked him recently for more information about the springs - he didn't send me all of the data I wanted though so I'll have to chase him up on that one...

...I'm a bit busy with other stuff at the moment though.

If you do change the ride height, this thread might help you set the suspension up afterwards

How I adjusted the toe in / out, camber and caster on my W123 300D

degier · #38 12-13-2012, 06:25 AM

Stretch,

Cool, but I can´t find the info on where to order the skid plate. I have a company registered. Maybe I can order myself...dunno. Otherwise my friend here in Trondheim.

Yeah I was happy with the ´86 model 300TDT, but surprised it didn´t have the ´85 model 2.88 diff. Luckily the 185 HR 15 wheel-size possibility will take care of that. Then again...you should see the roads here. Forget the zooming about with 130 km/hr like in the sewer delta of Europe (The Netherlands).

There´s a 10km bit of 100km/hr near Oslo the rest is some 90 bits, but mostly 80Km/hr intermittent with 70 60 50, and yes even 40 now with speed bumps, on the main E (european) type road through Norway!! I would be crying if it wasn´t such a joke. You should see those faces of the dutch tourists that come up here, ending up driving for days instead of enjoying their hard-earned holidays hahaha... Norway is so fizzing rich but with a road standard below the Albanian one.

Anyways...sorry for the detour, point is...the 3.07 differential might just be fine for the driving here.

Ok back to topic maybe? Oops..

Tacho, yeah...

Edit: found the page at MB and checked with the local MB pusher. 395 kroner ( =54 euro) so its is ordered. Cheers.

Stretch · #39 12-13-2012, 03:18 PM

Great I'm glad you got a skid plate for a good price - I got mine from "the dealer" you might hear about him being mentioned once in a while!

I don't worry about being off topic - as far as I'm concerned so long as it is kind of about cars then it is fine - and if you must butt heads about other topics then there's open discussion on this forum too...

...but let us know about how you get on with the tachometer!

degier · #40 12-13-2012, 06:55 PM

Okidoki,

Now that I have done the front end, sub frame etc...maybe time I get hold of such a FSM... hahaha.
No, serious, can´t find one as of yet. lol.

Just had a 4 wheel alignment done, but thanks. The front springs have the car sitting 1 3/4 inch higher than standard. Like the north african 123s. Wonder how much it will sink after the motor-swap. I also put a 15mm rear sway bar under it and heavy duty bilsteins are waiting in the garage.
It´s just so cold I´ll wait a bit with that. -20 C is too much for monkeying about.

Maybe the tach arrives before Norway shuts down for christmas. Now that would be worth ho-ing for.

Jan.

toomany MBZ · #41 12-14-2012, 09:50 AM

Model 123 Maintenance Manual Index

degier · #42 12-14-2012, 01:43 PM

This is great. Thank you.

Never came across this on my hours of searching, getting lured to download THE manual, and it turns out to be a Haynes.

The laughs, the tears...

See if there is a print button somewhere..

toomany MBZ · #43 12-14-2012, 02:00 PM

You're welcome, those are pdfs, so simply print 'em out.

Govert · #44 12-14-2012, 07:25 PM

Quote:

Originally Posted by Stretch

I get the feeling that they are meant for diagnostics only - something a mechanic would fit during a service but you wouldn't drive around with it fitted.

It is based on this tachometer I saw at the Technoclassica in Essen, Germany.

The cable looks like a speedocable, but possibly the cable has nothing to do with the tachometer. The tachometer is an early Euro model, with a red line.

toomany MBZ · #45 12-14-2012, 09:24 PM

I believe that's a gasser tach, different from a diesel?