Pompe hydraulique de carburant alternatif défectueuse

The pump that raises fuel pressure on a liquid-injection gas system has failed or lost output.

Its presence means this is a liquid-injection installation, which is a different and more sophisticated thing from the vapour systems most conversions use. An ordinary LPG system vaporises the fuel and injects it as a gas into the inlet manifold — which works, and costs a little power, because gas displaces air and the engine breathes less of it. Liquid injection keeps the fuel liquid all the way to the injector, recovering that power and cooling the incoming charge as the fuel flashes to vapour in the port.

The price is that the fuel must be held above its boiling pressure the entire way. That is what this pump is for: it raises tank pressure by several bar so the fuel stays liquid regardless of temperature.

Which is why its failure is abrupt rather than gradual. Losing the pressure margin does not weaken fuelling — the fuel flashes to vapour in the line and delivery collapses at once, characteristically under sustained load on a hot day. A driver will describe it as the car suddenly dropping back to petrol on a motorway climb.

Distinguish pump from system before replacing anything: the pump's own pressure sensor and the system pressure sensor exist precisely so that a pump making pressure into a leaking system can be told from a pump that is not making it. And find an installer familiar with liquid systems — a workshop used to vapour conversions may not recognise the hardware.