this is copied directly from that article:
"when the few ag diesels in use were started by gasoline pony engines or with compressed air."
The MD diesel was simply a model M, same features and options, but with International’s newly upgraded gas-start diesel. While the MD engine was of a similar design to the WD-40, it had five rather than three main bearings and displaced 248 cubic inches versus 460. They both made approximately the same belt horsepower, which illustrated the improvements in diesel technology. Like the older IH diesel, the MD was two engines in one. For starting and warmup, it operated on gasoline but was switched over to diesel operation. That was innovative technology in the day, when the few ag diesels in use were started by gasoline pony engines or with compressed air.
To start the engine, the driver operated a compression release lever opening a third valve in the cylinder head, called the starting valve, uncovering a separate combustion chamber that both increased the combustion chamber size and exposed the spark plug. With the starting valve open, the engine had a 6.75:1 CR and used a tiny, fixed-orifice carburetor designed only to run the engine at a fast idle. At the same time, the control disengaged the distributor ground, opened a fuel valve in the carb and a butterfly valve that connected the gas cycle combustion chamber to inlet air and closed the diesel intake.
The diesel side of the 248-cid gas-start four-cylinder diesel shows the IH injection pump and dual fuel filters. They took clean fuel seriously, with a water separator (glass bowl) followed by a primary and fine secondary filters. The injection pump has it’s own fuel pressure gauge that warns the operator when the filters are becoming restrictive.
The gas side (cough, gag!) shows the spark plugs, distributor and tiny carburetor. There was no driver-controlled throttle on the gas side. The carb was big enough to run the engine at about 800 rpm for warmup. When warmed up, you switched the engine over to diesel mode.
The engine was cranked over using a 12-volt starter and would idle at 600-800 rpm. This was enough to warm the engine up as long as needed for diesel combustion to be possible. Though there was a choke, idle speed was not controllable by the driver. After warming up the engine for one to three minutes, the compression release lever was pulled back briskly. That closed the starting valve, shut off the gas to the carb, grounded the distributor (killing the spark), closed the gas intake manifold and enabled the diesel injection pump. The engine then began running on diesel with barely a hiccup. For the shutdown, you switched back to gas and shut off the engine with the ignition switch, making it ready for the next start.
Keith,
I don’t quite understand your post. There’s no doubt many early ag and industrial diesels used pony motors or compressed air to start. The CAT RD6 is a good example.
What made these International diesels unique was they started on gas then you switched to diesel after warmup. The three paragraphs after the one you posted goes into detail. If you’re interested there’s a few good utube videos on them.
Hope your weathers warmer than mine.
John