i need help getting my tack to work. i recently installed a 1984 turbo diesel engine from a w123 in a 1980 euro 280c 4spd manual. everything works great except the tach. i have the 280c tach in the car but still have the 300d as a backup.
i cant find any wiring diagrams. the 'tach/diagnostic' plug unit on the drivers firewall appears to be the same. i dont have any m110 engine wiring so i dont know what was. i wired the sending unit at the flywheel directly to the tach but nothing. i put the speed sending unit on the back of the 280c speedo but took it off because it made the speedo irratic.

thanks don