Ayuh,.... If there's the required anti-siphon valve at the tank's outlet, the same thing occurs,... After all, it is a check-valve,...
I took the entire fuel system apart besides taking the whole tank out of the boat. There is no anti siphon valve and no check valve. I even had the sender and pickup tube out of the tank and replaced the 1/4 turn ball valve that attaches to the pickup tube. It snapped off while trying to get the pickup tube off.
@ Skippy - The reason I dont seem to like the bulb is that it doesnt seem to do anything by pumping it. While I have my fuel gauge and tester hooked up with the clear tubing and all I pumped that bulb for 20 minutes and besides it doesnt get hard (I know now you said it wont) I never saw any fuel go into the clear lines on my gauge setup. It just seemed like the bulb was just sloshing gas and air back and forth. Maybe not but thats what it seemed like.
I wonder if my bulb has an anti siphon doesnt seem like it because with fuel pressure tester hooked up (clear hose too) and when I turn the engine off I could see all of the fuel empty back out of the lines.
I looked at a couple check valves at a place locally called surplus marine but they seemed so hard to blow through and yes I was blowing through the right end I understand one way it should seal and not let any fuel (air) through. Decided since the boat is running good now Id stop messing with it and have some fun with it before the big weekend next weekend.
4th of July, fireworks, plus we have the powerboat races here. I stay off the water then.