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Goofy gas tank

I have a 2001 checy cavalier-- i have a hard time gettingit to start after the gas tank gets down to 1/2 tank- I have to crank it several times- when I fill tank all is fine until it gets back down to 1/2

full-- any ideas why it is doing this?

This is usually caused from a weak fuel pump. The fuel pump is located at the bottom of the fuel tank. When the gas tank is full, the level of gas in the tank produces what is called head pressure. This head pressure assists the weak fuel pump in delivering the proper fuel pressure to the fuel system. As the level of the gas in the gas tank drops, the head pressure also drops to where it no longer assists the weak fuel pump. This results with a fuel pressure that’s below spec, and makes it difficult to get the engine started.

Have the fuel pressure tested when the gas level is close to half full, and I bet you find the fuel pressure is below spec.