Just installed a 496HO in an Formula 242LS, and the tach does not work?
 

Everything else works, just had to swap the oilpressure senor
to one that uses the same signal type as the gauge.

But the tach is dead?! After some looking i found out that
there is another tachwire on the engine for "analog" gauges.

Tried to connect that wire to the tachometer but with the same result.

How do I proceed? Can I measure the signal somehow?
To see if there is any signal? I dont think the gauge is broken?
If possible I would like to keep the original look on the dash...