MJ/XJ Instrument cluster ground

So the entire gauge cluster in the MJ has gone dead. I'm thinking it may be a ground issue. Does anyone know precisely where the instrument cluster ground is on an '89 MJ? How about a '91 XJ? My XJ did the exact same thing about ten minutes before the motor blew. In both cases the temperature, voltage, and oil pressure readings froze in the normal operating position. The only immediately obvious symptom is the gas gauge which is pegged way past full. Tried a different cluster in the MJ tonight with no change.

I just had this problem start yesterday.. need info too ! Mines a 89 XJ. My gas gauge and temp gauge is pegged, rpm dont work, alt meter is at 9v or something