WIRING A TACHOMETER TOP DIESEL ENGINE

Tachometer Wiring — The Art of Diesel
Because diesel engines don’t have a coil to provide an ignition signal for the tachometer to measure, we are forced to find other ways to get a signal that’s proportional to engine rpm. One way to get a signal would be to use the “P” connection on the 140-amp (CS144) alternator’s “SFLP” plug.[PDF]
SWP 118031 Diesel Tachometer Installation Instructions
Start the engine and determine the actual engine RPM using a reference tachometer (optical, non-contact tachometer recommended). Check all of the wiring connections and power to the tachometer. SWP 118031 Diesel Tachometer Installation Instructions