when i put gas in truck car won't start without pressing gas peddle to the floor

You need to replace the purge solenoid valve on the motor $40. That will solve the problem.

Owner, It sounds like the engine is trying to operate with too much fuel, this could be caused by a host of possible faults, including faulty fuel injector, faulty oxygen sensor, coolant sensor circuit open, possible evap system fault, Hint: never add more fuel after nozzle shuts off when filling tank.

This is caused by continuing to add fuel to the tank after the first cutoff by the gas pump. You are flooding a valve in the fuel system and also the charcoal canister will be soaked by the overflow. The solution is to have Cadillac replace the valve. This will allow the car to start correctly and the cost is minimal. The canister is your option. It costs a lot of money to replace because it is locater in the rear bumper. You will smell a strong gas odor after filling up if you don't replace it. It will not catch fire but it is annoying.