Tacho failure

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The Big Man

New Member
Joined
Dec 3, 2008
Messages
7
Hi All,

The tacho on my E300D (W124) has recently stopped working after a period of bouncing up and down to zero when the car was at lower revs. Above 3500-4000rpm it seems to want read every now and again. The engine idling is very rough as if the OVP relay fuse was blown, but its not and I have changed the relay from a friends car to check it. Also the rear demister will only operate for about 5 seconds and then it will begin to flash and not operate although it is producing heat at the window for the time it is on.
The car is really smoky in the mornings now but the glow plugs are working as it would definitely not start without a preheat

Anyone out there know what`s up?
 
I'm not sure but your pump may have an electrical timing advance for cold starts so bearing this in mind it sounds like you have a bad connection somewhere.

Try wiggling wires around to see if it improves.
 
Had the same problem on the tacho with my G-Wagen. It was a dry joint in the signal amplifier box. (couldn't repair it as it is potted).
 
I'm not sure but your pump may have an electrical timing advance for cold starts so bearing this in mind it sounds like you have a bad connection somewhere.

Try wiggling wires around to see if it improves.

That's interesting as the idle on my e300d is not as good as it once was when it is cold - and the symptoms started right after everything was disturbed to change all the glow plugs. Once warm it is fine. Can you tell me more about this - where I would find it etc etc; thanks.
 
That's interesting as the idle on my e300d is not as good as it once was when it is cold - and the symptoms started right after everything was disturbed to change all the glow plugs. Once warm it is fine. Can you tell me more about this - where I would find it etc etc; thanks.

Air leak. Change all the O-rings

Nick Froome
www.w124.co.uk
 
Air leak. Change all the O-rings

Nick Froome
www.w124.co.uk

Nick, been there - done all that! inc the black main feed pipes where they terminate at the rear of the engine bay. Still misbehaves a little when cold - like a misfire on a petrol engine. I have an idea it may be a bit of valve seat regression - but thing is it has been doing it for the last 50k miles and is not getting any worse. And it started straight after I had an indi change all the glow plugs - since then I have had it all apart myself to try to find the problem.
 
I'm not sure but your pump may have an electrical timing advance for cold starts so bearing this in mind it sounds like you have a bad connection somewhere.

Try wiggling wires around to see if it improves.

DM, can you let me have some more info on this please?
 

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