2000 Hyundai Accent Fuel Pump

Fuel supply is the one that brings the fuel to fuel rail, Fuel return is just that it returns unused fuel to the fuel tank and the vapor line is for emission and returns fuel vapor to the gas tank through the vapor canister

Thanks for your reply.In case of pump check valve faliure, which line fuel going back to tank either fuel supply or return.

The supply line

Can i hold the pressure, by installing check valve for the supply line, what is best location of the line for that

The fuel pump will still not hold pressure it is built into the pump the only way to fix it is to replace the pump. So even if you put a check valve inline it will still leak down at the pump if that's the only way you can fix it then as close to the tank as possable