Jumpy Tach Prob

I have a SW Wings Electric drive Tach in my roadster that at idle reads correctly. When I put my foot in it, it jumps all around. Is it interference from my plug wires? Other issue? Ground is good...

THANKS!

 

Try rerouting the pickup wire but it sounds like ground. How good is good?

 

I have the same problem. It's in my '39 Ply, w/flat 6 engine. The needle would bounce around while accelerating and at idle would jump around every 30 seconds or so. I sent the tach back to Speedway and they promptly sent a replacement. The second tach is better but still bounces at idle. ???????

 

Will try this. Also will take an alligator clip and jump the ground to another grounding point.

Thanks much

 

I used to have problems with electric tachs, similar to what you are talking about when my points were bad.

 

I had that problem in a challenger with eletronic ignition the ecu was not sending a very good signal replaced the ecu then the tach worked fine i dont know what you have for an igntion but that worked for me.