The importance of electrickery and your mechanical speedometer (W201/W124 based)

[Stretch]

G'day Folks,

I thought I'd post up this nugget of information in a separate thread.

Coming from a simple / old fashioned vehicle / diesel background I've been struggling with KE CIS systems.

User supercow sent me a whole load of information that I diligently read. Reading the foot notes I came across this =>



So on SOME W201s and W124s with Bosch KE fuel injection systems there's a Hall effect sensor on the output of the MECHANICAL speedometer cable.



Number 5 in the picture above.

So if like me you have random stalling and fluctuating revs and you've mistakenly thought the operation of your mechanical speedometer was not important - think again!

Note also =>

Error codes for road speed sensor B6 are not stored in the "computer" as usual. Switch off the ignition and they are gone!

Drives me effing mad this KE ****...

[Zulfiqar]

nice work,

the hall effect switch is present in cruise control cars and also was used to lock the outside temperature display in later models. So it would not read the hot exhaust from the car infront of you in a traffic jam.

[Stretch]

Yep and mine's a basic 4 speed manual gearbox vehicle. Nothing fancy on it!

I get the feeling (so I need to check this) that anything with the last generation KE system has this road speed sensor. So in year terms from about 1990 you might have to consider this...

[porkface]

i've fixed stalling in many a car by replacing that speed sensor. mentioned it a few times, too but i never heard if there was a fix. good luck, chuck.

[Stretch]

Originally Posted by porkface

i've fixed stalling in many a car by replacing that speed sensor. mentioned it a few times, too but i never heard if there was a fix. good luck, chuck.

Thanks - I'm sure other people have mentioned it too.

I made the poor assumption that the operation of a mechanical speedometer would have no effect on the electrickery in the car.

If you are a bit of a dinosaur like me you might not immediately make the connection between mechanical speedo and a fault with your CIS

[gatorblue92]

This could explain the random stalling I sometimes have in the 300TE if I press the clutch in to coast to a stop. Item #8 was on the side of the automatic I removed when I converted to a 5 speed and it is somehow connected to the part you posted.

[Stretch]

It sounds like I get the same problem.

The following happens =>

Drive like you're driving Miss Daisy and only dip the clutch when the revs get to about 1000rpm when changing gear or coming to a halt and the idle "is caught" and stays where it should.

Drive a bit faster and have the revs above about 2500 rpm and dip the clutch and the idle drops like a stone - you have to be quick with the gear change to catch the idle before it stalls.

If I can, I'll make a video of the event before I fix the speedometer.

From all the chat on the internet on the subject of random stalling this fault points to a dodgy EHA. I've had problems finding the connectors to check the fuel pressures though, and I've not been "doing the quarter turn" tuning trick because that sort of thing in my experience just causes more trouble!

[w123fanman]

I believe this could be bad on my car, just haven't gotten around to pulling the instrument cluster. I have the sensor from my parts car that I believe was good sitting on my workbench waiting to go in. Car idles like crap.

[Dr. Sternschnuppe]

Speed signal is used for KE-Jetronic on M102 & M103 from 09/1988 & 09/1987 respectively.

[Stretch]

Originally Posted by Dr. Sternschnuppe

Speed signal is used for KE-Jetronic on M102 & M103 from 09/1988 & 09/1987 respectively.

Great stuff - thanks for that.

[Stretch]

Originally Posted by w123fanman

I believe this could be bad on my car, just haven't gotten around to pulling the instrument cluster. I have the sensor from my parts car that I believe was good sitting on my workbench waiting to go in. Car idles like crap.

In my experience I (think I) have learnt the following.

Electrickery =>

1) You need a "clean" power source - that means no leaky diodes on your alternator

2) You need a good OVP

3) The air idle control valve needs to be clean and to operate properly

4) The temperature senders are important

5) The O2 sensor needs to send a reliable signal

6) The pulses from the rear crankshaft sensor are important not only for the spark in the plugs but the CIS too

7) The air flow potentiometer is a big wear problem! (CIS air flow potentiometer possible fix?)

8) The hydro-electric actuator is a twat

9) New plugs leads and cap are a must

Fuel =>

1) Fuel pressures are a bugger to measure because of the silly sized unions used by Mercedes - a dedicated kit is expensive

2) Injectors don't last forever!

3) The plunger for the fuel distributor can stick

4) If the electro-hydraulic actuator leaks then there's trouble - but it is only two little (thicker than normal!) O rings





#########



In your case I'd start by looking at the air flow sensor tracks and perhaps change the O2 sensor.

The problem I have is a good steady idle for most of the time but occasional drop of death (usually on a round about so the power steering dies too!)

[Stretch]

Speed sensor part number is 0075421917

VDO part number is 340.213/006

Data for testing is here =>



I'm gonna try and test it before I replace it at this little piece of junk costs about 50 euros at the dealership and I can't find it for much less elsewhere.

[Mohammad]

Sorry to Revive this Thread after So long.
but I have a 2.5-16 that I Swapped the Engine to a later Model M104 320.
and I Kept the Manual Gearbox.
the Problem Now is that the Engine Doesn't Rev Past 4K !
I read Some where that Pin 8 on Plug On the ECU Needs Speed Signal.
so will I Solve the Problem if I Wire Green/Yellow Wire from this VSS to the Pin No. 8 ?
the Engine Idles Perfectly and Pulls Very Strong "until it reaches 4k " then Starts to Cutoff.

[optimusprime]

Mohammad see you found the usa forum ? I did say it was your best bet . [ 190e forum ]

[Mohammad]

Originally Posted by optimusprime

Mohammad see you found the usa forum ? I did say it was your best bet . [ 190e forum ]

Yep.looking for any answer that might Help.