Rev Counter Circuit Diagram

[davemar 16]

I'm trying to work out why my rev counter works fine with a Jetronic setup, but doesn't work very well with a Motronic setup. Does anyone have a circuit diagram of the rev counter itself? I've googled high-and-low and the closest I've found is a photo of the back of the PCB. I don't really fancy dismantling my dash to try and decude the circuit.

[cybernck 402 1 Cars]

It should work exactly the same with both really, so I'd try with finding the problem elsewhere.

[welshpug 1,657]

which motronic setup? one that takes a signal from the coil like the Jetronic or one that supplies a tacho signal from the ecu? if the latter it wont work.

 

if the former, it should and you probably have a dodgy connection somewhere.

[davemar 16]

It's the Motronic ML4.1 that takes the signal from the coil. Knowing the circuit will give me a better idea of what the signals should be like.

[Anthony 1,003]

If it's ML4.1 then the rev counter should work exactly as per an 8v, since it's getting exactly the same input as an 8v.

 

I would look at the loom rather than the tacho if you're sure it works fine on an 8v.

[davemar 16]

I now think the rev counter is telling the truth, it's the ignition signal that's not right. It's easy to forget the rev counter isn't telling you revs of the engine, but the firing of the ignition. While the engine seems to be running OKish, I did notice when the rev counter show a little dip, even though the engine revs was steady there was a little pop from the exhaust. Also I tried driving a short distance (with the bonnet half open!) and one under load the engine misfired quite badly.

 

So it seems I've got a problem with the ignition signal side of things. Ho hum....