1994 Ford Probe GT MSD External Coil HEI Module Wiring Diagram

This is a hand-annotated wiring diagram titled "MSD External Coil HEI Module Diagram," drawn by community member "bencollinz" and dated 1/28/05, labeled for a 1994 PGT MTX (Probe GT, manual transmission). It shows how to wire an MSD Multiple Spark Discharge ignition box together with a GM-style HEI module and an external coil onto the factory distributor harnesses. The 3-pin distributor harness supplies a yellow/black wire (not used), a yellow/blue wire, and a black/pink wire; the 6-pin distributor harness provides the disty ignition input on a blue/orange wire routed to the HEI module. The MSD box's RED, WHITE, BLACK, and ORANGE leads are spliced through inline connectors: the WHITE wire passes through a 1,000-ohm 1-watt resistor path to the HEI module, and the BLACK and ORANGE leads connect to the external coil's + and − terminals. The MSD's heavy RED and BLACK power leads go directly to the battery positive and negative terminals, the magnetic pickup connector is not used, and a tach output is available on the MSD box. The HEI module terminals are labeled W, G, B, C, and GND, and a sketch of a "modified disty cap" (distributor cap) is included. The author notes the diagram is for visual purposes only.