service engine light is on.
tech say it is something in the evap system.
when i try to pump gas, the lever always clicks off.
i can't pump gas into the tank..........
i can gravity some gas into the tank.
at some point the gas comes out the fill pipe.
when i start the car, the gauge shows only 1/4 full.

 

I don't know if this applies to you, but I replaced this on my 2001 blazer theres a pressure switch located right on top of the pump unit on the tank.

If thats defective it will not allow gas in to the tank. I did not have to drop the tank all i did was reach pver the rear axle and removed it by pulling it loose from the top of the pump.

There's also a small electrical connector on this as well. You can get it from auto zone for $40, i believe it called a fuel pressure switch

 

another thing to check is the anti roll over valve inside the filler neck at the tank. they like to stick causing fuel to back up when filling. there was tsb that i found because my parents impala was doing the same thing. pull the filler neck off and see if the valve moves freely if not clean it. i cant remember if its in the tank neck or the filler neck.

 

You need to have the evap system tested, either something is telling the vent solenoid to close or it is stuck closed. The vent solenoid allows fuel vapor to escape so that fuel will fit in the tank, If the valve is closed the fuel can`t fit due to too much air in tank causing back pressure.