شیر قطع مخزن سوخت جایگزین معیوب

The electrically held valve at the outlet of a gaseous fuel tank — LPG, autogas or CNG — has failed, seized, or lost its control circuit.

It is a safety device, and reading it as a fuel valve underplays what it is for. A gaseous fuel tank holds its contents under real pressure: around 8 bar for LPG on a warm day, up to 200 bar for compressed natural gas. A petrol tank leaks a puddle; a gas tank leaks continuously and invisibly until something ignites it. So the tank outlet carries a valve that is held open electrically, wired so that it closes whenever it loses power — engine off, ignition off, crash sensor triggered, or any fault in its own circuit.

That fail-closed design is why this failure has no middle state. The valve is either held open or the tank is isolated; there is no limp mode. On a bi-fuel car the engine simply reverts to petrol and keeps running, which is why the complaint that reaches a workshop is "it will not run on gas any more" rather than anything alarming.

And it is why the fault is easy to live with and worth not living with. A circuit that intermittently fails to hold the valve open is the same circuit relied on to close it on demand. The half nobody notices is the half that matters.

Two practical notes. These installations are usually aftermarket, so the letter in the code maps to a physical tank only in the installer's documentation — a car may carry a toroidal tank in the spare wheel well and a cylinder in the load space, each with its own valve. And the work belongs with a gas installer rather than a general workshop: the tank must be handled correctly before anything at its outlet is disturbed.