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  #1  
Old 07-10-2016, 06:51 AM
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Join Date: Feb 2015
Location: Kansas City
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Where does the 190E 2.6 tachometer get its signal?

Hello,
Sorry if similar questions have been answered before, but I have not had much luck searching.

I will be converting a 1993 190E 2.6 to diesel, and I wish to reuse whatever OEM components I can to make it as much of a 'plug-and-play' swap as possible.

First off, can anyone please confirm that the M103 gets its RPM gauge signal from the three timing tabs on the flywheel, through the crankshaft position sensor?
I know the diesels receive the tachometer signal from the crank pulley, but the gasoline engines do not.

If the signal does indeed come from the crankshaft sensor, I already have the M103 manual flywheel with the correct timing tabs, so it will just be a matter of using the M103 crankshaft position sensor.


However, the position sensor connects to the ignition control module, which is where things get confusing.



Is it still necessary to retain the ignition module for the RPM signal?
I know I will not need any of its other functions anymore. Could I just splice the wires from the position sensor directly to any of the wires that go to the RPM gauge? If so, would it be A4 or A7, or any of the others?

Or does the ignition module convert the reading from the crankshaft sensor into correct signals for the tachometer, so it will be necessary to keep it? If so, will it still provide the RPM despite none of the other sensors being connected?

I know this is a lot of questions in one post, but I am hoping someone will be able to shed insight on it.
Thank you for any information.

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Old 07-10-2016, 07:22 AM
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Diesels sense RPM from the flywheel, at least the 2.5's do.

The signal from the sensor is not sufficient to drive the gauge. It's modified by the engine electronics. How about using the tach and EDS module from the new motor? That way it all plays together nicely.
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Old 07-10-2016, 08:06 AM
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Interesting. How do the diesels read the RPM since the flywheels do not have the timing tabs? Do they just count the starter ring gear teeth?

The motors I have are OM603 and OM606, so the tachometers from those cars will not be a direct fit, nor did they come with the sensors or any electronics. Also, sorry for being dumb, but what is the EDS module? Is it the diesel car equivalent of an ECU?

However, if the diesel sensor does just count the flywheel teeth, then I am guessing the components from the 2.2 or 2.5 190D may work.
What would one need to scavenge from a diesel W201 at the junkyard in order to make the tachometer function properly?

Thanks again!
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Old 07-10-2016, 08:56 AM
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To operate the existing tachometer these components will be required:
A flywheel with three tabs.
The existing crank position sensor to sense the flywheel tabs.
The ignition control module (EZL).

The EZL signal that drives the tach appears at pin A4 (TD).
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Old 07-10-2016, 09:08 AM
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Quote:
Originally Posted by Frank Reiner View Post
To operate the existing tachometer these components will be required:
A flywheel with three tabs.
The existing crank position sensor to sense the flywheel tabs.
The ignition control module (EZL).

The EZL signal that drives the tach appears at pin A4 (TD).
So it should work if I already have all of those components?
Even if none of the other pins (camshaft sensor, coils, knock sensor, etc.) are connected to anything on the diesel engine?

Thank you.

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