A check valve restricts the flow of a liquid or gas in a piping system to one direction.
Inside the gas tank.
NO it can not as there is a check valve located in the filler neck.
You do not because there is a check valve in the filler to prevent gas spillage in case of a rollover.
If you measure "the applied voltage" (typically, 24 volts) across the coil of the main gas valve, and the valve refuses to open, it will need to be replaced. Before you do, double-check that gas is getting to the valve.The HVAC Veteran
Check your vacuum lines and also check your idle air control valve. Make sure the IAC valve gasket is in good condition and that the valve itself is not loose.
Exhaust gas recirculation valve fault
A dual check valve is similar to a double check valve in that it is a mechanical backflow preventer consisting of two independently acting, spring-loaded check valve.
If the pilot flame is too high a thermocouples life could be shortened. Check the specs of the unit supplied by the gas valve for the working pilot pressure. Or put the gas valve in pilot and depress the pilot push button. Keep the button down with a small screwdriver, remove the thermocouple from the gas valve and check the millivolts on the thermocouple. Place one lead on the copper tubing and the other lead on the end of the thermocouple, the silver looking part that touches the inside of the gas valve. With the pilot flame on you should read anywhere from 22-29 millivolts. Anything below that is a sign that your thermocouple is failing. It might work for awhile, but it will probably go out in the middle of a long cold winter night. ;)
A redundant gas valve is a safety feature in a gas system where two valves are installed in series to ensure that gas flow can be shut off if one valve fails. This redundancy helps prevent gas leaks and potential hazards.
The fuel level in the carburretor float chamber is too high. A leaky float valve is more likely than a punctured float. However, check the petcock is not on 'PRI' first.
Usually gas appliances come with an extra valve in with the instructions. Just replace the valve. You may have to ask a heating specialist how to find the connection on your gas line. But it is not too difficult.