A combination spark-ignition/Diesel engine was actually built by International Harvester back in the late 1940’s, and installed on the Farmall “M” series tractor. The design was a switch between gasoline spark-ignition, on which the engine was started up, then, while running, a lever was engaged that pushed a slide-through casting that effectively reduced the volume of the combustion chamber, raising the compression ratio, sealing off the spark plug, and starting the injection pump on the Diesel operation. The sealed-off spark plug was switched off from firing, and the engine went on full Diesel operation. The original reasoning was that Diesels were notoriously hard to start from cold, and took a HUGE starter motor, using about 24 volts, to get the first charge ignited on the Diesel. This compromise made it possible to start the engine with a 6-volt system, or a hand crank if necessary, then enjoy the virtues of higher thermodynamic efficiency once the engine was running.
There never were very many of these old “MD” semi-Diesels around, as they were a pretty finicky piece of machinery. But when they ran right, they could beat the gasoline model for pulling power and relative fuel economy under load.
Actualy the concept was used throughout the IH line during the 40’s & 50’s. They made in addition to the farmall M versions, I believe about 40 drawbar HP, equal to the W-6,a W-9, and tracked versions TD-9, and TD 14. They also made stationary versions for pumps and Generators. They were easy to start in cold weather.
Didnt the military have a multi fuel engine that used the same system in the 70’s
barbra ann