Now i got the tachometer fixed! But the needle still did not move! So here is a clever solution i got from the guy that sold me the engine management system that i think will work on other systems to and perhaps on the Msd.
It is just a ordinary relay with a small fix! You just put it in parallel between the +12v cable and the signal cable to tach
+12v cable to tach is first connected to number 86 on relay and then to tach.
Signal cable to tach is first connected to number 85 on relay and then to tach.
It is a very simple way to get an volt peak to get the tach needle to trigger!
I think the Msd box for tach is just the same in a nicer package