If you fly glow powered planes, you may get a lot of advice about how to keep dirt and particles out of your airplane’s fuel system. Some people will tell you to use a fuel filter on your fuel jug, but I am telling you not to. Here’s why.
When you fuel your plane, you pump fuel from the jug, through the pump, into your plane’s fuel tank. If you have a filter on the end of the pickup line in your jug, particles will get trapped on the screen and you will avoid fouling your tank. So far so good. At the end of the day you connect your pump to the plane and pump any remaining fuel back into the jug. It’s possible that you may have contaminated your fueling probe with dirt, in which case the dirt will go through the pump and be deposited on the other side of the screen in the fuel filter in your jug. Next time you pump fuel into one of your planes this dirt will go into the tank.
You could set up a system where you pump fuel through one filter to put it in your plane and through a different filter to take it back out. Or you could use one filter for fueling, but bypass the filter for defueling. I don’t like the complication.
A long time ago I made a very simple fuel jug that has served me very well for decades. It has no filter, and it uses only silicon fuel lines, a clunk weight out of a fuel tank, a crank pump, and a fueling probe made from a piece of brass fuel line. Here it is in storage position. The fueling line is wrapped through the handle several times to make it more compact.
Here it is, ready to fuel a plane.
Here’s a view into the mouth of the jug. You can see that the pickup line goes down into the fuel. It has a weight on the end, which hangs one or two inches above the bottom of the jug. The other line is just a couple of inches long, with about an inch on the outside of the jug and an inch on the inside. This line allows air to enter the jug while the fuel is being pumped into the plane, and it is where the fueling probe is parked for storage.
Here’s a diagram of the system, to help you discern what’s going on.
To build this system you need a sharp 3/16″ drill bit. Drill two holes near the top of the jug. Make sure the holes are very neat and round because a jagged hole will not seal. My jug can be turned upside down and it will not leak. Cut the ends of your fuel lines diagonally, so you can stick the pointy end through the hole. Reach into the jug with a pair of long nose pliers and pull the lines through. Put a clunk weight on the end of the pickup line and pull enough line through so it hovers above the bottom of the jug.
That’s all there is to it. The reason why it works is because if you ever get dirt in your fuel, and you will, it falls to the bottom. The hovering line can’t pick it up. I’ve been using this fuel jug since 1992. (Actually I’ve gotten a new jug and a new pump once in that time, but it’s the same system.) The only time I ever got dirt in my fuel tank was when I had only an inch of fuel left and I tipped the jug to get the fuel out because I wanted to fly one more time. It picked up the dirt from the bottom of the jug. Other than that, I don’t have dirt problems. When the fuel level gets below a quarter of a jug I pour some in until it’s about 3/4 full.