I have a 91 coupe the car used to be a 4 cylinder with an automatic, now it has a 306 with a Tremec. The tach didn't work when I bought the car. I replaced the insturment cluster with one from a 92 with 140mph speedo. The tach still doesn't work. When I turn on the key the tach will jump and then do nothing, so I know it has power going to it. I don't know what else to try please help. Thanks.

 

Anyone?