Westerbeke 44B Admiral Control Panel

[AnnOMalleys]

Are there any signals from the control panel back to the engine that would effect how the engine is running?
Here's the scenario. - been working on engine. Started her up today, the tachometer has stopped functioning. Still getting the light, but the tach is not showing RPMs. When I started the engine, the tach spiked to about 3500 rpm, then went to zero, and stayed there , no matter what rpm. All other Gage's working correctly. Ran engine for about 10 minutes, various RPM, no response from tach. Tried tapping / shaking panel to see if that would do the trick. As soon as I did thAt, the engine started running roughly. I shut engine down, and called it a day. To the best of knowledge I do not have the fuel shutoff solenoid
So, why would shaking the control panel cause engine to run rough?