The classic International Harvester tractors from the '30s, '40s, '50s & '60s had engines that started cold on Gas and switched over to diesel once warmed up.
The combustion chamber had an additional valve that opened up to a pocket which decompressed the chamber to allow for gas operation. There is a mechanical lever that a person would shift to switch over to diesel operation after the engine warmed up. This lever cut off fuel to the carburetor, the magnito for spark and closed the valve for the pocket. It also allowed the Injection Pump to operate to provide diesel fuel.
Here an excerpt from an old IH TD-6 crawler ad.
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