The fuel tank on my plane has three lines. One to the carb, one to the muffler, and one to fill. The tank is completely hidden from view. My question is, how do you know when the tank if full of fuel, other than waiting to see it coming out of the muffler! This obviously floods the engine every time. Is there a better way? By the way, the lines are hidden behind a cowling, so it's not possible to easily disconnect the line to the muffler.

You can unplug the pressure line that goes from the fuel tank to the muffler. When the tank is empty, fill it with your hand pump and count how many turns it takes until fuel starts coming out the pressure line. This will give you an idea of how much fuel to put in. You can do this after each flight and figure about how much fuel you use for each flight, then use that many cranks in the future.

I don't think fuel going into the muffler when you fill is that big of a deal, as long as you are paying attention and stop filling at the first sight of fuel. Whatever is in the muffler will blow out when you start.

since the muffler is hidden in the cowl of my Hangar-9 P-40 I used a small nylon T fitting,I got it from the local Ace hardware, to make a alternative vent line off the muffler pressure line, when I fill the tank I pull out some of the slack, and pull the plug on the line,placing it in a small cup to catch the fuel.
then when I fill I either hold my finger over the muffler end or I have a little plug that fits the rubber diverter,works great.
the aluminum bracket is drilled so the fuel line slides freely,but the allen head screw wont slip through.

I tried the extra vent line. Waste of time for me. I have never had any flooding problem waiting for fuel to exit the muffler.
If you use an electric fuel pump you can hear a change in pitch as the tank gets near the full point.

i don't think you'll flood your engine fueling. the fuel that comes out of your muffler is usually not from passing through the engine but straight from the vent line. i think you'll be fine. as mentioned above, i would count how many cranks when i used a manual pump. i'd count how many seconds when i used an electric pump. but everytime i'd fill her up until i could either see fuel from the muffler or fuel filling the vent line.

good luck!

If you close your throttle, and set the trim to 0 (minimum), it should not go into the engine via the fill line if using a third fuel line.

What I do is use a two tube system. One from the tank to the carb, and one to the muffler for pressure. I disconnect the muffler tube and connect a fuel overflow tube from my fuel supply, then connect the pump line from the fuel supply to the carb end of the fuel feed line (disconnect it from the carb) and fuel it that way. When the tank is full, it runs back into the fuel supply via the pressure tube.

I've done it this way for years, and, no, it has not "contaminated" my fuel supply. This method is required in many clubs, by the way.. fuel recovery systems.

You don't have to use all three lines provided in the tank system.

But, if you want the three tube method, using a fuel dot on the fuel-up line, and setting the throttle to closed with the trim to zero will eliminate any fuel into the carb.

CGr

You really can't flood the engine by adding fuel to the muffler unless you add A TON. Fuel in the muffler has already passed through the engine. The only thing you'll notice is that your engine will spit out quite a bit of raw fuel for a few seconds after you turn on the engine.

You also waste quite a bit of fuel by allowing it to flow out of the muffler. If it's in the right position, you could be throwing away a couple ounces per tank full. This is why I use the fuel recovery system on my fuel supply. Nothing spills, and nothing gets wasted.

CGr.

Depends on the engine and installation. I've seen plenty of setups that would flood quite nicely if you pump fuel into the muffler, I even have a handful of planes that do it. If I forget to pull the line from the muffler, the engine floods FAST when the tank gets filled.

On cowled installs where you can't reach the carb or muffler fittings, I usually mount the engine on it's side, and that totally prevents flooding from the muffler. Inverted 4-strokes are also not a problem, and most inverted 2-strokes have the muffler outlet lower than the engine's exhaust port, but not always.

On upright engines, it depends a lot on the shape of the muffler (and sometimes the landing gear of the plane or slope of the pits if any). Some old engines have the exhaust port on the bottom of the muffler, while on others the engine's exhaust port enters the side of the can, giving plenty of volume to catch fuel before it drains back into the engine.

Btw, if you raise the piston by turning the engine up to compression, you block the exhaust port, and that will help keep fuel from draining back into the engine.

I love that idea of using a T in the pressure line and plugging the muffler for fueling, I'll have to set that up on some of my cowled engines where I currently just let some fuel come out of the muffler. I already usually use a 3-line tank because I find using a fuel dot is the simplest way. Reaching the carb line is just not possible with a 4-stroke hidden inside a cowl.

Oh, I forgot, on my cowled engines, I can usually find an angle that allows me to see back into the cowl and look at part of the vent line that goes to the muffler, even if I can't reach it. Sometimes I can only see a short bit of a loop and not the end. While I'm fueling, I watch that line, and when I see fuel, I stop the pump, and that reduces the amount of fuel that gets into the muffler.

Fuel will absolutely flow into the exhaust port of a two stroke engine if the piston is below the port. Also, if the piston is high, and the piston skirt doesn't completely cover the exhaust port, then fuel can run in underneath the piston, into the crankcase. Either way you can get a flooded engine and hydrolock. As said before, this most often happens on two strokes that are mounted upright. I have a kadet with a .52 evo on it that will flood and hydrolock everytime I over-fill it, if I wait for fuel to come out of the muffler.

That is the best way.

I also use this set up and works fine, the only difference here is that I attach a spare fuel tank that I carry on my tool box and shut the pump off when fuel is starting to get to the spare tank (I attach the tank to the alternative vent line off the muffler pressure line).

I should have made my first post a little more clear - but I think you guys have gotten me on the right track. My engine is a two stroke mounted on its side (which is why it floods when fuel goes into the muffler?) with a pitts muffler flowing out the bottom. The pressure line to the muffler and the fuel line to the carb are impossible to get to without removing the cowling (which I obviously don't want to do every time I fuel). If I were to put a "T" in the pressure line, and plug it for flight and unplug it during fueling, would fuel not go through the pitts muffler if I were to come up with two plugs? I hope I am making sense.

you put the T fitting on the pressure line inbetween the fuel tank and muffler,then when your filling just plug the exhaust holes on your pits muffler the overflow will go out of the open line out of the bottom to your catch container.
I am going to start using a extra tank I have thats a good idea(alfredbmor).
then replace the plug in the overflow and unplug the muffler,or just take your fingers off the exhaust tubes and there you go, by plugging the muffler holes the fuel will be diverted to the overflow line and not to the muffler canister,on the photo I posted the line is just inside the cooling fins so its out of site but easy to grab and pull out enough slack to drain into a cup,when I am finished fueling, I just plug it and slide the fuel line back in,its pretty easy and takes little time at all.
the nylon T I used has barbs so the fuel/pressure line won't slip off as well.

I see a second fuel dot in my future - one for fuel in and the second for overflow fuel!