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3-line tank, why won't it fill ?

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3-line tank, why won't it fill ?

Old 04-02-2006, 06:15 PM
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Default 3-line tank, why won't it fill ?

As I pump fuel into my tank using a 3-line system, it will reach half full and then the pressure builds up then starts to empty the tank thru the vent line as well as the feed line pouring new fuel into the carb and muffler. I pinch-off the feed-line entering the carb and I get a gyser out of the vent line... what's up with that?
In a minute the fuel stops leaking and the pressure in the tank seems equalized but the tank is not quite half-full !. THe engine starts & runs fine this way on the test stand, as I want to test this tank before it goes in the plane after I break-in the engine.. it's a 14oz clear tank and the vent line is pointing up inside the bubble, the pick-up is plumbed correctly and the fill-line...well it's just the fill line!. Any suggestions for solving this...THanks for reading..
Old 04-02-2006, 07:09 PM
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Default RE: 3-line tank, why won't it fill ?

Sounds sort of like you have the fill & vent lines reversed and are filling through the vent/pressure line at the top.

You can also get some "splash" out ot the line by filling too fast.
Old 04-02-2006, 10:55 PM
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Default RE: 3-line tank, why won't it fill ?

I'm afraid I'd have to agree with Ed on his conclusion. Sounds like the lines between the fill line and vent line connection are switched. I run a 3 line on all of my planes. In the stopper coming out of the tank the 3 tubes should form a triangle (point up). I always make the bottom two lines in the tank identical. Each line has a tube with clunk on it. The top connection is bent so it goes to the top of the tank, which it sounds like you have correctly. With the two clunks on the bottom lines, not only do you provide the engine with the proper set up, but when your done flying, and you want to de-fuel, with the clunk on the fill line, you can get all the fuel out easily. I also always make sure the throttle linkage has the throttle in the kill position, helps to make sure that the engine isn't flooded. The one thing I added last season to my fueling system since fuel is so expensive is a fuel catcher, to catch excess fuel when the tank does go full and it comes out of the vent/muffler line. I just took a small 10oz fuel tank with clunk, and added a fuel nipple to the end of a short piece of hose that easily slips into the line running from the tank to the muffler. I simply disconnect the muffle line, slip in the nipple to the small tank, start to fuel, and when the planes tank is full the excess goes into the excess tank. I reverse the fueling button, suck out the small tank, and go fly. Saves a mess from soaking a table or in the grass. Wish I could post a picture, but I think if you do a search MinnFlyer has several drawings of this setup.
Old 04-05-2006, 03:52 AM
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Default RE: 3-line tank, why won't it fill ?

sounds to me like Gputt33 has it i clunk my fill line no probs here

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