DEEP TECHNICAL CONTENT
LPG fuel system
LPG fuel system: Automotive LPG is mainly a propane/butane mixture stored as liquid under pressure. The page also includes a worked example and measurement sequence.
Technical frame
LPG fuel system: Automotive LPG is mainly a propane/butane mixture stored as liquid under pressure. The page also includes a worked example and measurement sequence.
The technical values here expose the standard, protocol or physical relationship directly; model-specific service values are linked through the matching model/variant dossier.
The goal is not only to define the term but to let the reader calculate and interpret what the data means in a scan, scope or physical test.
Concrete technical facts
- Automotive LPG is mainly a propane/butane mixture stored as liquid under pressure.
- A regulator/vaporizer can use engine coolant heat to vaporize liquid LPG, so low coolant flow can cause pressure/temperature problems.
- Propane stoichiometric air-fuel mass ratio is in the ~15.7:1 class; actual LPG changes with propane/butane composition.
- LPG injector duration can be derived from petrol-ECU base injection through correction/mapping.
- Gas pressure, manifold pressure and gas temperature together affect injector mass delivery.
- Petrol/LPG A/B fuel-trim comparison helps separate common engine faults from LPG pressure/calibration faults.
Worked example
- Example: if combined trim is +3% on petrol and +20% on LPG under the same MAF/MAP/mechanical condition, LPG pressure, injectors/nozzles and calibration become stronger suspects.
Measurement and verification sequence
- Record fuel pressure/temperature and operating mode.
- Correlate lambda/fuel trim with commanded injection.
- Use an A/B fuel-mode test where possible.
- Perform leak/pressure tests with fuel-specific safe equipment.
Fault-separation logic
- Is a valid command present and are power/ground/network healthy?
- Does feedback follow the command?
- Does an independent physical measurement confirm the output?
- Is the fault limited to a specific temperature/load/speed condition?
- Does the result remain stable when the original condition is repeated after repair?
Technical sources
Continue investigating
Model-specific real technical data · Measurement references · Technical diagnostic atlas