skypiratescotty

My Feedback: (32)

This has me baffled and I hope someone can help. I have a Pheonix Super Decathlon 40 with a ST 75 on it angled at 7 o'clock looking from the front. I test ran the engine on the bench 3 times and it ran perfect. I bought the airframe from a guy who had already assemled it and after I put the engine on I tried to fuel it. That didn't go so well as I got maybe three turns on the pump and fuel began to pour out of the carb and exhuast vent so I disassemled it to find that he had the vent line touching the bottom of the tank. Anyway, I re-plumbed the tank to match every tank I have done in the past ( I've put together at least 20 planes) and fuel still comes out of the carb as soon as I get a prime on the pump. I did take it all apart the other evening and the carb is located along the centerline of the tank. I'm lost on this one so if anyone has ideas I would really appreciate them!!

Scotty

jbdismukes

My Feedback: (2)

Did he "T" the fill line into the carb pickup line?

CGRetired

My Feedback: (1)

To give more detail, draw a sketch of the way your tubing runs and post it. That way we will all have the benefit of seeing what you are seeing and perhaps help a bit better.

CGr.

skypiratescotty

My Feedback: (32)

Sorry, I don't know how to post a sketch but I just closed the needle valve (high speed) and was able to get a full tank into it. This is how I have it plumbed: carb line runs into tank left front and clunk almost touches back of tank, exhaust vent enters tank beside carb line and brass tubing is bent up to almost touch top of tank and fill line goes thru cowling right into the very top front of tank ( which makes it impossible to use to de-fuel). I think I'm gonna get a Sullivan tank and be done with it!!

Scotty

opjose

Yeah, when you are putting fuel into the tank you are also forcing fuel into the carb as well....

Your problem is not with the tank but with your plumbing.

First make sure that your vent line is clear and permits good flow. You may have a clogged nipple that is permitting pressure to build up in the tank, forcing fuel out of the tank-to-carb line. Check and clear the nipple at the muffler.

For cowled setups on smaller planes I prefer something like this with a two line setup.



which permits fuel ONLY to flow into the fuel tank during fueling.

BTW: "almost touches the back of the tank" is not a good idea.

During acceleration or uplines the fuel tubing will stretch and you can end up cutting off the flow of fuel to the carb as the clunk hits the back of the tank...
( this was responsible for a very hard to find problem on one of my planes... )

Leave at least 1/3-1/2" from the back of the tank for safety.

skypiratescotty

My Feedback: (32)

I used to use a fill valve like that on a World Models Ultimate 40 and it worked great!! I'm gonna look for one next time I get to the hobby shop in a couple days.

Thanks for the advice and I will shorten the clunk just a hair, I think I'm about 1/4" from the back of tank right now.

Scotty

1320Fastback

Get a Quick-Fill valve. When the fueling they block off the carb line and send fuel to the tank.