Cause
Faulty alternative fuel hydraulic pump
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.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (25)
Codes where this is a likely explanation first, rather than merely a possible one.
- P2A70 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit Likely for this code High
- P2A71 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Range/Performance Likely for this code High
- P2A72 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit Low Likely for this code High
- P2A73 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit High Likely for this code High
- P2A74 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit Intermittent/Erratic Likely for this code High
- P2A7F Alternative Fuel Pump A Compression Stroke Valve Control Circuit/Open Likely for this code High
- P2A80 Alternative Fuel Pump A Compression Stroke Valve Control Circuit Range/Performance Likely for this code High
- P2A81 Alternative Fuel Pump A Compression Stroke Valve Control Circuit Low Likely for this code High
- P2A82 Alternative Fuel Pump A Compression Stroke Valve Control Circuit High Likely for this code High
- P2A83 Alternative Fuel Pump B Compression Stroke Valve Control Circuit/Open Likely for this code High
- P2A84 Alternative Fuel Pump B Compression Stroke Valve Control Circuit Range/Performance Likely for this code High
- P2A85 Alternative Fuel Pump B Compression Stroke Valve Control Circuit Low Likely for this code High
- P2A86 Alternative Fuel Pump B Compression Stroke Valve Control Circuit High Likely for this code High
- P2A87 Alternative Fuel Pump C Compression Stroke Valve Control Circuit/Open Likely for this code High
- P2A88 Alternative Fuel Pump C Compression Stroke Valve Control Circuit Range/Performance Likely for this code High
- P2A89 Alternative Fuel Pump C Compression Stroke Valve Control Circuit Low Likely for this code High
- P2A8A Alternative Fuel Pump C Compression Stroke Valve Control Circuit High Likely for this code High
- P2A8E Alternative Fuel Pump A Performance Likely for this code High
- P2A8F Alternative Fuel Pump B Performance Likely for this code High
- P2A90 Alternative Fuel Pump C Performance Likely for this code High
- P2A75 Alternative Fuel Hydraulic Pump Pressure Sensor Circuit High
- P2A76 Alternative Fuel Hydraulic Pump Pressure Sensor Range/Performance High
- P2A77 Alternative Fuel Hydraulic Pump Pressure Sensor Circuit Low High
- P2A78 Alternative Fuel Hydraulic Pump Pressure Sensor Circuit High High
- P2A79 Alternative Fuel Hydraulic Pump Pressure Sensor Circuit Intermittent/Erratic High
Information, not instruction
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