While the diesel engine has been falling out of favor in passenger vehicles, they remain reliable and powerful workhorses keeping the gears of industry spinning. The diesel engine has been the prime mover of agricultural vehicles for a century. However, the diesel powerplants of a century ago suffered from a major headache, one that International Harvester solved by building engines that started on gasoline first before switching over to diesel fuel.
According to Farmers Weekly, the diesel engine found its way onto farmsteads beginning in the late 1920s. The first diesel tractor is sometimes credited to the 1927 creation of Italian engineer Franceso Cassani, the founder of Società Accomandita Motori Endotermici (Same) tractors. But the Americans weren’t too far behind. In October 1931, Caterpillar introduced its Diesel Sixty Tractor. McCormick-Deering later introduced its own diesel tractor with the WD-40 in 1935. John Deere spent so much time trying to perfect its diesel engine design that it was a late entry that came out in 1949.
While these companies were able to get diesel engines chugging in tractors, early diesel engines suffered from a problem that had a number of potential solutions.
The Problem
One of the problems facing diesel engines even today is being able to start up in cold weather.
Diesel engines work on compression ignition rather than spark ignition like gasoline engines. Diesel fuel is a reliable source of power and if you’ve played with the stuff before you’ve probably noticed it’s usually harder to start on fire than gasoline.
However, one of the downsides of diesel fuel is how it “gels” up in cold weather. As diesel is subjected to weather usually at or below freezing, the paraffin wax in the fuel begins to crystallize. The further this happens, the harder it is to pump the fuel through an engine’s fuel system. In a worst-case scenario, your diesel engine may stall out, if it even starts to begin with. The exact temperatures diesel begins this process varies based on the quality and type of fuel. For example, biodiesel may begin gelling at higher temperatures than conventional diesel.
The diesel engine has been around more than long enough that there are plenty of ways to combat this, as well as the general slog of starting a giant diesel in the cold, too.
Your first line of defense is an anti-gelling additive, something I use in my diesels during the winter. Your modern diesel engine also has glow plugs. These devices sound similar to spark plugs, but they’re used just to get your diesel engine going. A glow plug has a heating element that gets glowing hot, heating up the incoming fuel and air during the starting process to encourage combustion. Bosch says its first glow plug was invented in 1922 while Denso had its own glow plugs in 1929.
Of course, there’s also the engine block heater, which helps you get going by making sure the whole engine isn’t a giant block of frozen to begin with.
The diesel engines of nearly a century ago were old-school. Farmers had to start rather sizable engines by hand cranking, but even starters sometimes weren’t enough to wake up these early diesels from a wintry slumber. To give you an example of this, the Cat 60/65 crawler had a 1,090 cubic inch engine while the IH TD-40 was still a huge 460.7 cubic inches. Both engines technically used hand cranking to start but needed help from gasoline to get going.
Cold weather cranking issues sent manufacturers scrambling for a solution, and the results were very different.
The Engine That Runs On Two Fuels
We’ll start with the way many fans of tractors may know about.
Manufacturers like Caterpillar and John Deere employed what is called a “pony motor.” The pony motor is a much smaller engine attached to the side of a monster tractor engine. These gasoline engines would fire up, rev to 4,000 RPM or above, help pre-heat the diesel fuel, and then is clutched into the main diesel engine, spinning it over until it started.
Many early pony engines were small twin-cylinder mills while others were slightly bigger V4s. Check out this video below to see a pony engine on a John Deere:
Apparently, pony engines lived hard lives. They were started up, run hard, and then shut down. Farmers would often forget to maintain these units and they would suffer from carbon build-up before eventually dying. Those pony engines would then end up replaced with a 12V starter or some other solution, so seeing an old tractor with an original working pony engine is a treat.
As Successful Farming writes, John Deere spent over 14 years developing the Model R and in that time, its engineers considered making an engine that started on gasoline before settling on the design with a pony engine starter.
International Harvester? Well, it went forward with a multi-fuel design.
As Diesel World writes, International Harvester began experimenting with diesel power in 1916. The company’s first engines were of its own design, but in 1927 IH began picking four-cylinder Dorner engines from Germany to study. At the time, those Dorner engines were smaller and lighter than their American counterparts with advancements not seen on this side of the pond. Over time, IH’s engineers would take what they learned from the German engines to create something of their own design.
Among their goals was solving the problem of cold weather starting and one day, IH also wanted its own fuel injection system. IH also wanted to produce moderate-cost engines that produced decent power on poor fuel.
Part of why IH didn’t go with a pony engine was because it was believed a pony engine was bulky, expensive, and made engine starting harder than it needed to be. That bit’s a little amusing since IH’s solution looks almost hopelessly complex. IH went through a lot of work to make a diesel engine briefly run on gasoline, from Diesel World:
[T]he essential feature of a gas start diesel was an auxiliary combustion chamber connected to the main diesel chamber by what was called a starting valve. When that was opened, the added volume of the auxiliary chamber dropped the compression ratio from 15:1 to about 5:1 and it contained a spark plug fired by a magneto. The gasoline intake tract was connected to the diesel system via an air valve. A small 3/4-inch bore carburetor supplied enough air and fuel to run the engine at about 400 rpm. A lever connected to various linkages opened or closes valves to the various chambers and disabled either the magneto or the injection pump. It worked better than you might think, especially when viewed in the context of the era when “diesel” and “cold starting” were exclusive terms.
The first generation IH diesels would be manually switched over to gas engine for starting and hand cranked. No, these first engines did not have electric start. The injection pump had a timer that counted the number of engine revolutions (about 700) and it could be used optionally to automatically trigger the system to switch back to diesel operation after approximately two minutes running on gasoline. In most cases, two minutes of running was enough to warm the engine enough to run on diesel but the operator could run the engine on gas as long as needed.
IH was cool enough to explain everything in its brochures, so I’ll pass that down to you.
A spring-loaded rod (1) opens the starting valve (3) which combines the gas and diesel combustion chambers. The lever also moves a poppet valve in the gasoline system from a lower seat (7) to an upper seat (9). A gasoline valve (6) also opens to fill the carburetor (10) and air flows into the intake (8) to the combustion chamber. Another rod (2) levers a valve, which shuts off diesel fuel flow from the injection pump, which isn’t pictured. Releasing this Rube Goldbergian system once the diesel engine is running turns the gas system off.
Yep, that means these were diesel engines with a gasoline carburetor, distributor, and a spark plug for each cylinder.
Diesel World continues that this engine, dubbed the PD-40, was initially based on IH’s existing gas engine architecture. This allowed some existing tooling to be used and thus made development a little cheaper. The engine made its debut in April 1933 and its exact specification varied based on application. This engine in a crawler was a TD-40 while it was called an ID-40 in an industrial tractor, WD-40 in a wheeled tractor, and UD-40 as a stationary generator.
The coolest application of this 461 cubic inch four-cylinder diesel was in the McCormick-Deering TD-40 TracTracTor crawler tractor. I mean, just look at it!
That straight-four was good for 62.5 flywheel HP with a continuous power rating of 50 ponies. The engine was also good for 48 HP at the power take-off.
Oh and don’t worry, you bet I have a starting procedure video for you:
Reliable Workhorses
IH would keep these engines in production for three decades, improving them along the way for better reliability and power. Additional variants included the PD-80 six-cylinder in 1936, the TD-40 and TD-80 second-generation gas-started diesels of 1939, the smaller UD-6, UD-9 and UD-16 engines of the same year, and the massive UD-24 of 1947. How big are we talking about here? The UD-24 was a thick 1,091 cubic inches and made 146 HP.
Observe the sheer girth of this bad boy:
Ultimately, the IH gas-start diesels were complex, but they were proven to be reliable engines. Diesel World notes that these engines often made less power than the competition. However, these engines were able to start reliably when the competition did not. The IH gas-start diesels were smaller and more user-friendly, too. Though, it’s noted that some would prefer the pony motor design since engines with those for starters were arguably better at being bigger, more powerful diesel engines.
IH wasn’t the only producer of this idea. In the late 1940s, Lamborghini used the architecture of a Morris Six engine to create a fuel atomizer that allowed its diesel tractors to start on gasoline, too.
Either way, the pony motor versus gas-start debate was eventually resolved once technology finally caught up. Diesels that could start in any weather made these stop-gap technologies obsolete. But, for about 30 years if you were a farmer, there was a good chance you had a diesel engine that also ran on gasoline.
Hat tip to Oliver!
Lots of military trucks were multi-fuel back in the day.
Actually had one of these repurposed in a terminal I operated to drive machinery. Loved the reaction when new mechanics were asked to go change a spark plug on the diesel…..
Another good video here of an International starting on gas and switching to diesel at the 1m mark. Thanks for dipping into #agtopian (#tractopian?) territory!
Just a Few Acres Farm did a restoration of a Farmall MD
When I was a kid my grandfather had a standby power plant on his farm which was powered by a Waukesha spark-diesel engine–inline six if memory serves me. I loved starting it up enough that he put me in charge of running it through a weekly exercise cycle. It started on gasoline and after about fifteen seconds you’d switch it over to diesel which actually ran off the heating oil tank in the building.
Awesome! Such interesting history
I love the name TracTracTor
We had one of these in our fire house. Came off a civil defense truck from the 1950s. The motor was in a tiny block building that was about the size of a closet and like a foot of clearance on each sign. Absolutely terrifying starting this thing and then switching it over to diesel. I remember the fan in the front didn’t even have a shroud! Back then, safety third and it’s more important to get electricity down into our underground bomb shelter!
I can see where IH was coming from. Lots of tractors and industrial engines start on gasoline and switch to kerosene. Briggs & Stratton cataloged dual fuel into the late 80s.
We had a John Deere that ran on gasoline, kerosene, and LP gas.
My grandfather would drive it to the railroad siding to get 600 gallons of kerosene in barrels loaded into a wagon.
Once he took it all the way to to the Richmond Chevron refinery. Turned out that taking a tractor and wagon from the Central Valley to The Bay Area was non trivial in the 1930s
By the time I was using it we used gasoline only.
I’ve heard of these engines as well, while I’d love a David Tracy deep dive on this I think they burned kerosene in a spark ignition method by preheating vs compression ignition which I believe you can also do with kerosene.
Must have been spark. It had a carburetor but not fuel injection, and I think compression ignition requires fuel injection.
By the time I was born, it had lost its multi fuel capabilities and had some random truck carburetor put on it. I think there was some method of heating the intake manifold or something that had been cut off with an acetylene torch.
A really worn Detroit Diesel can runaway if the rings were shot enough to allow enough oil from the crankcase to blowby into the combustion chamber.
Fuel could be shut off from the injectors, the Green Leaker wouldn’t care, kept on running
Had to stuff a towel in the intake or dump the clutch on a high gear to stall it out.
Back in the 90s, I worked at an armored car company. Of our large over-the-road trucks, we had one with a Detroit in it. I knew some co-workers who had served in the Navy in the 1950s and 60s; they said you always kept a handful of rags or a CO2 fire extinguisher (or both) on hand in anything powered by a Detroit — in case of a runaway. If one of them was driving that truck, they always checked to make sure there were some shop rags tucked in the cab — and grabbed a few if they’d gone missing.
Great article!
I worked on a barge that used a 1943 Bucyrus Erie crane and was pushed by a tug called Wildcat, a steel 40 footer with 30″ wheel and and an old Detroit Series 71. The crane would not start under about 40 degrees without the pony motor, but once the little diesel took over it was an amazing piece of machinery. It was a friction crane and so much faster than the hydraulic rigs we had on land. The tug was steel and the engine was just sitting open in the bilge with zero sound insulation. When you would get to the job site after steaming at about 5 knots the engine was hot enough to cook breakfast on, which was always a nice way to start the day.
My Dad bought a 50’s IH TD-9 when we moved out to a farm in the early 70s. Thankfully it never got cold enough for us to worry about the fuel gelling, and it had a couple of big 12-volt batteries cabled in series to power a 24-volt starter. The “cool” weather starting procedure was to spray a puff (and ONLY a puff!) of ether into the air intake and then hit the starter. Repeat as necessary.
The problem of cold-starting a diesel turned out not to be intractable.
Bump starting a a Mercedes-Benz diesel is the sort of thing you do once , and it makes a really funny story, sort of like Top Gear done by the three stooges, but it’s not something that anybody ever tries twice.
what is the deal with bump starting a diesel? I used to do it a lot of times on the family tractor back in the old country when huge batteries were hard to come by. A lot of people would just leave the tractor parked on a hill and bump starting when needed.
I remember after the fall of the fall of the iron curtain people started getting beat up old Mercedes diesel vans in the country, and same problem with the battery availability. They would be either started by parking on an incline or be pulled to start. That has been 34 years ago, and I was my early teens at the time, so details might be hazy, but I do remember bump starting the tractor. I even did it for fun during my last visit there about 10 years ago, just for the old time’s sake
Tractor is one thing, Diesel automobile with cold glow plugs, and not a whole lot of traction in the rear is something else.
Step one , get the big Ferguson. The much more suitable Ford 8n was at the other end of a half mile of foot deep mud so you take what you get.
First gear on the gravel road, not nearly enough traction. Second gear moving right along until we run out of road. Go get another tractor go follow behind, The locals are used to slow moving tractors, slow moving Mercedes not so much. Pull out onto the highway en convoy. Pop the clutch n second gear. Leave big skid marks on the highway. Let the clutch out slowly, and the engine starts turning over. But it’s not starting, what it is doing is emitting huge clouds of white smoke. Well, I guess the engine needed a little more heat in it. Let’s just keep going for a quarter mile. This is obviously not working so we stop because another half mile we would have to cross some railroad tracks and it seems like a terribly bad idea. Rummage around find a can of ether and spray that into the intake on the Mercedes no the thing about starting a diesel on ether is that since there’s no throttle it’s a little unpredictable how much power the engine is going to generate until it runs out of ether. So of course, the engine starts, wants to make lots of power, wants to the ram the tractor, and puts slack in the chain. So then, whoever is in the Mercedes, I think it was my mom, has to use the brake enough to not hit the tractor, but not so much that it takes the slack out of the chain and rips the bumper, or whatever we have the chain attached to, off the car.
Eventually, the two tractors and the Mercedes came to a stop without any collisions or ripping asunder of automobile.
Anyway, that’s the last time We tried that. Bump starting tractors? No problem. Hand cranking engines that are meant to be hand cranked? Well that’s the natural order of things. Going to CBGB in the 1970s in a Volkswagen that you had to push to start? Of course, even got some help from a couple of Hells Angels. But that’s the last time I want to get involved in starting a Mercedes diesel by towing it.
It’s jokes like this that choke.
Yes apparently.
The Me262 had sort of a pony engine- a 2 stroke with a pull start in the nose cone of the the engine to spin the jet up
it was pretty common at one time to have multifuel tractors. the old Oliver 70 KD started on gasoline and would switch over to Kerosene once warmed up. I believe they could run on heating oil and regular diesel too, but like all things multipurpose, they were ok at a lot of things, but not great at anything.
Jesus, what was redline, 500 RPM?
My dad had a John Deeere B gas that was rated for 17 horsepower with 149 cubic inches, two cylinder, you didn’t need a tach, you could just count exhaust “pops”
That reminds me of the old Hit n’ Miss engines. What a delightfully simple way to govern engine speed.
I have a huge fascination with engine technology from that era between the experimentation and the patent avoidance so many cool things were tried
Suck, bang, repeat.
If the interwebs are reliable tonight she’s listed the drawbar horsepower. Engine max was 191 at 1400rpm, 180 at 1375 intermittent, so that drawbar sounds about right.
Ignition systems in the early days were a constant demand for ingenuity for both gas and diesel engines. This is why there were such things as “hot bulb” engines that kind of bridged the gap between spark and diesel ignition. It’s a pretty long bridge, too: the compression ratio in a hot bulb engine is almost comically low.
“This engine in a crawler was a TD-40 while it was called an ID-40 in an industrial tractor, WD-40 in a wheeled tractor, and UD-40 as a stationary generator”
Fun fact: It was also called a UB-40 when running on red red wine.
Really well done article. Thanks!
We had a John Deere 730 Diesel but it had 24 volt electric start instead of the Pony motor. Interestingly, we almost never had to use the block heater. It was a big 378 CID 2 cylinger (later bored out to almost 440 CID). It used a decompression lever and the started would get the big 200 lb flywheel spinning. When you released the decompression, it would start firing.
Or you can start it by grabbing the flywheel, at least after it’s been running a while.
More of an impress the visitors thing than a useful get work done thing.
I’ve done that exactly once, on a 70 gasser. It was warmed up but the charging system wasn’t hooked up so I couldn’t restart it once I shut it off. I was standing a little close and the damn thing tore the zipper right off my coat. I fixed the charging system immediately after that and it’s been in regular field use for the last 2 years!
One of our John Deeres had a magneto. You could start it cranking extraordinarily slowly. You would just sort of creep up on top dead center and bang! it was running.
Ours had the covered flywheel. I have heard that you could take off the center cover, remove the steering wheel, and there was a special thing to hook it in and start the tractor with that. I have never tried.
I work at a CNH dealership and it’s pretty fun to stump people on this one hah
This was an awesome idea and a useful one! Not to mention (in theory) it could be possible to have an engine that can switch and just use gasoline all the time if diesel is hard to get for some reason. It would not be as powerful, but it would be a good backup. Either way this is an interesting concept.
The Gasodiesel? The perfect engine for my Thundercougarfalconbird!
Hand cranking a 1090 cubic inch engine?
Farmers really are built different.
Thelma! Get the horse!… I Gotta Start the Tractor again!
Mostly they weren’t directly cranking the engine. They’d spin up a big flywheel and then use that to spin over the engine.
Kinda like how they started big radial airplane engines.
There was that, and also the Coffman “shotgun starter”. Those are fun!
The fancy term is “inertial starter”, which kind of explains how they work. The nice thing about them is that they can work on any source of power that can get a flywheel spinning fast enough. Hand crank was the slowest way, then there were electric and air starters as well. They make interesting noises in operation, too.
It’s not THAT hard.
Those pony engines, they are the worst.
There were worse things some early Caterpillar tractors were started by sticking a crowbar in the flywheel.
That was fascinating. I love the sound of big diesels idling.