how to make the magic happen with a dead tacho
 

Hi
Many of you have been following my project w126 with the OM603 engine, but which actually started life as a 500SE

I have fixed my cluster problem which was a broken circuit board channel which connected the earth on the middle board.

But if anyone has any suggestions on how to get my tachometer going, that would be bloody marvelous. Where to look at the other end of that cable would be a great start.

thanks


MJ

Diesel cars require the diesel tachometer head, there is no substitute or workaround. The gas cars use the ignition pulse from the ignition module for tach readout, the diesel count flywheel teeth. Additionally, the tach pulse for the 603 engines comes from the EDS computer. If that wasn't transferred to your swap, you do not and never will have a usable tach pulse unless you get some sort of aftermarket tach setup.

You've completely ruined my day.

Well, not really. The fact you have an OM603 actually gives you a chance to install a tachometer as you have the "missing tooth" on your flywheel. You might even have the pick-up sensor still in its spot.

Sourcing the actual in-cluster tach/clock head might be a problem but it is a lot better than having to pull and replace the flywheel.

Wiring and sourcing the tach amplifier might be your biggest challenge.

thanks Mike. Can you elaborate a bit? Where would i look for this pick up sensor ? And what exactly is the "head" you're referring to?

best


MJ

Google is your friend.

The "head" I am referring to is the clock/tach option in the instrument cluster.


Attachment 161143

I know is possible to make the tach work I’m interested in how to do it because I have a 91 300CE with a OM603

Well, i presently have three tacho clocks in my possession, so maybe one of them hits the jackpot. But don't know where to start with the job.
Why don't you start a thread, as i can see others in the forum who would also like to benefit from your experience.

You need a Tach gauge from a 603 powered W126. Since that seems to have been a US-only thing, you're probably going to have to source a tach gauge from a US market car, 1986-87 300SDL or 1990-91 350SD/SDL. The OM603 was really only used in the W124 in Euro markets and the tach heads are physically different. The quickest way to tell if you have a tach from a gas car is to look for the red area in the rev range. Gas cars have it, diesels don't.


You have a car that's been hacked together with who knows what parts by someone with an unknown level of skill. You're going to have to resolve yourself to the fact that the factory wiring diagrams and traditional knowledge on these cars isn't going to apply much to yours. There's going to be a considerable amount of things you will have to track down and diagnose on your own or find a mechanic that can do it for you unfortunately.

Great. Thats' a start at least. But what about the sensor? Where is it? How do i see if at least its there?
thanks

MJ

Crankshaft sensor is on the driver's (Left) side of the engine under the starter motor.

https://www.benzworld.org/attachment...00-jpg.333378/

My 1990 Dodge with the 5.9 Cummins did not come with a factory tach. There are after market tach set ups that have you put a magnet on the crank sprocket with a sensor mounted to count each pass of the magnet. that may be an option for you.

Here's a thread to follow:

http://www.peachparts.com/shopforum/diesel-discussion/410425-anyone-know-what-happened-bob-techguy512.html

Every time I read the title of this thread I think its about doing something sexual with a dead taco. ;)

Wow.