Operating Pony Motor Trailers: A Quick Guide for Drivers
If you’re hauling liquid nitrogen, oxygen, argon, or CO2, chances are you’ve got a pony motor behind the landing gear while you’re driving. It’s important to know the specifics of your trailer to ensure proper care and operation, especially when starting it up. Some of these motors can be a bit stubborn in cold weather.
Most of these will be powered by a Kubota or Kohler 4-cylinder diesel engine, but there are still some old-timers in the industry with gasoline engines. It’s exceptionally important to identify the proper care and fuel before you fire it up. The motor is paired with a pulley system that drives belts to spin the pump in the cold cabinet. Proper adjustment and alignment during maintenance are a must.
Key Tips for Operating Pony Motor Trailers
- Start with a Good Inspection
- First things first, take a really good look at your trailer before you take off. Be especially observant when you’re picking up a new trailer. Check the fuel, oil, and coolant levels, check for leaks, and make sure it’s not making any crazy noises. As mentioned above, when you’re getting a different trailer, make sure of the fuel type. Though rare, there are probably still gasoline pony motors out there in the wild.
- Side note: Pony motors were originally referred to as a pup engine or cranking engine. They were all gas powered and used to crank diesel engines or larger gas engines without the need for a battery. A pony motor was a gas powered starter for tractors and dozers and such.
- Warm it Up
- When you fire it up, don’t just crank it and go. Let it run for a couple of minutes, especially if it’s cold outside. Engines like to be warmed up a bit before doing any heavy lifting. Speaking of cold weather, these diesel motors are prone to fuel gelling in below freezing temps. Be sure to use plenty of diesel treatment or they won’t start at all.
- Don't Overload It
- When you’re pumping, keep an eye on your pressure gauges. Push it too hard and you could burn up your belts. Stick to the limits for whatever you're hauling to avoid any nasty surprises. Someone once told me that a discharge pressure of 75 psi over the tank pressure was a good rule of thumb. If you smell burning rubber, you may want to shut it down and investigate.
- Watch Your Fuel
- Make sure you’re keeping track of how much fuel is left in your little tank. Last thing you need is to run out in the middle of a delivery. Keep it topped off. You don’t want to know the regret you feel when the pony motor starts sputtering a half hour before you’re done with the delivery. Also, plenty of fuel treatment in the cold. Redundant? Yes. Important? Yep.
- Keep Up on Maintenance
- These little motors don’t ask for much, but they do need regular care. Tend to your maintenance and pay attention to any odd behaviors that develop. Keep it clean—dirt and grime can clog up the works fast.
Troubleshooting the Usual Problems
- It Won't Start: Check the basics — fuel, oil, air filters.
- It's Overheating: Look at coolant levels and make sure nothing's blocking the airflow.
- It's Losing Power: Fuel filter could be clogged, or maybe the spark plugs need attention. It could also be loose wiring.
Safety Notes
- Shut off the pony motor if you're refueling or working on it.
- Keep the area well-ventilated if you're running it indoors.
- Have a fire extinguisher nearby — just in case.
Final Thoughts
Running a pony motor trailer isn’t rocket science, but paying attention to the little things can save you big headaches down the road. Keep it maintained, fuel it up (and treated), and listen for anything out of the ordinary. Stay safe and keep those loads moving!
Photo: Kubota D1005