Alright guys. I appreciate the responses I've gotten so far but I still can't find how the tach hooks on my 78 300D. There's no magnetic picup on the front of the crank. Nothing I can find around the flywheel. I have the motor and trans out on the floor so it's easy to look the whole deal over. But I can't find anything that might read engine rotation .
Likewise there was no plug on the back of the tach. Just a 2 prong jack for attaching a plug. Anybody have any ideas?. I'd like to put the gauge cluster into my 240 and hook up the tach since the 5 cyl will be there too but don't have a clue how to make it work.One of you MB tech guys has got to know. Thanks.

Well you got me confused.

The only diesel that would have had a tach in 78 would have been the 300SD (116 body). The cluster for a 116 body is not likely to fit either a 115 or 123 body 240D anyway.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve, thanks for the response. But if I understand you correctly, there shouldn't even be a tach in a 78 300D, correct??
The cluster from 300 is physically the same as the cluster in my 240 and will fit but the 300 cluster has the tach. Any idea how to make it work? I might could get the sensor and mount it (if I can find out where it's supposed to mount ) and run a wire to the tach.Thanks for any help.

The tachs on 300D turbodiesels used a sensor reading off the front crank balancer till 1985. In 1985 the read the engine speed off the flywheel.

The sensor on the front of the motor sent the signal to a transducer that converted the induced AC signal into a squarewave pulse that the tach would accept.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician