E30 speedo revs not working after engine change

[Zubair541]

I Had my e30 converted from 318i cabby to a 2.5 now the speedo or rev meter dont work everything else seems to be fine the temperature and fuel gauges work fine I also had the cluster changed but didn't make a difference what could it be??

[Brianmoooore]

What age is the 2.5?

[e30mtech]

check pin 9 on c101 should be black on both ends (body and engine) mine had same problem on my 316-325 as stevie wonder had wired up my car very badly

[Zubair541]

The 2.5 is out of a pre facelift

[Brianmoooore]

The 2.5 is out of a pre facelift

Chances are that this used a three pin plug, separate from the 20 pin C101 plug, for the tacho and fuel rate signals. If this is the case, you won't have the black wire on pin 9 of the engine loom that e30mtech refers to, as it ends in the 3 pin plug that is probably hanging off the engine loom near the ECU. The same applies to the fuel rate signal.
You have three choices to sort the problem:
1) (By far the best) Upgrade the management system and engine loom on your pre facelift engine with a M1.3 motronic system from a later M20 engine.
2) Cut off the three pin plug, extend the wires back through the bulkhead, across and into the C101 plug, and connect them to the correct pins.
3) Obtain the matching three pin socket from the car the engine came from, open up the loom that goes to your instrument cluster, find the two wires that are currently going to the body socket side of your C101, cut them, and splice them to the three pin socket.