ORIGINAL: JohnW
Chuck, thanks for the info.
Joe, in a way you answered my question too. If you tank is puffing up, then the engine is using crank pressure to pressurize the fuel system for the injector, i.e., the engine is not pumped like the 140DZ. The DZ does not use a check valve in the return line. Fuel pressure for the injector is provided by a pump incorporated with one of the push rods. Sidebar, you may wish to consider using a different tank. It is possible for a YS to burst tanks. There are many tanks that will work... in general stay away from flexible tanks. Look for Dubro or Sullivan rigid wall tanks.
I admit I was not confident making that statement about it having a pump but thanks, now I understand how it works better. The engine is on a FuntanaS and the stock tank fits perfectly so I just wrapped it in strapping tape. The RCU review stated that they tried Sullivan and Dubro tanks and they didn't fit in the nose of the plane like the stock one. All the seems are covered in strapping tape. Hopefully this does the trick.
Joe