I purchased a Sig 4 star 40 recently and flew it for the first time yesterday. When I feuled it up the first time I had no problems hand cranking the feul into the tank. The plane flew very well. When I tried to fuel it up a second time, I attached the pump tubing to the fuel line to the tank, disconnected the line to the muffler and started cranking as I always do. After about 20 seconds of cranking the tubing from the pump seperated from the tubing to the tank with much force spraying fuel over me and the plane. I am afraid to fly the plane for fear of the tank being bad. I can blow thru the tubes (lines) and they seem to be clear. I tried refueling today and had the same results. It appears the tank is full.
Can someone tell me what is going on. This is only my third plane the first 2 I assembled myself and had no problems. I have no contact with the person I bought the plane from so I can't ask him.

One possibility is that the clunk on the end of the fuel line has flopped into the front of the tank and kinked the hose. Ideally you could remove the tank and look. If the tank is not accessible hold the model verticle with the nose up and shake it real hard. That usually will move the clunk to the back of the tank. Did the model flip over on the first landing? That will sometimes flip the clunk into the front of the tank.
Chuck

the clunk in the tank might had gotten sholved forward during
the landing, therefore the fuel line might be pinched.

i usually hit former #2 (behind landing gear)
with the palm of my hand as i swing the fuselage down
to un do kink on a plane with the fuel tank area glued and enclosed.

you can grab the nose of the plane and swing the fuselage

when building a 4 star . i usually make with a hatch option.
becuase of this problem. it's an easy fix with your 4 star
even if it's glued.

sometimes if foam or padding is not installed in the tank.
and depening how the line is routed.
the tank gets sholved forward. a kink is develope between
the tank and firewall

I did "nose down" while taxiing back to the pits after the first landing. The tank is wrapped in foam & would be a real pain to
take out. I will try what you said and let you know, thanks.