LPG car servicing: a guide for LPG and dual-fuel owners

LPG (autogas) and dual-fuel cars are still common around western Sydney, from Falcons and Commodores to converted vans and utes. They need the same servicing as any petrol car plus attention to the gas system itself, which has its own parts, its own wear points and its own compliance rules. This guide covers what gets checked, common faults, the NSW compliance basics and when to have the system inspected.

How an LPG system works, in brief

LPG is stored as a liquid under pressure in a tank, usually in the boot, tray or under the car. It travels through a fuel line to a converter (also called a vaporiser or regulator) in the engine bay, where engine coolant warms it and turns it into vapour at a controlled pressure. From there it’s fed to the engine, either through a mixer on older systems or through gas injectors on newer vapour-injection systems. Solenoid valves (lock-offs) shut off the gas when the engine isn’t running or when you switch to petrol.

Every one of those parts can wear, block or leak, which is why the gas side needs regular attention.

What gets checked in an LPG service

Exact service items depend on the make of gas system, so follow the schedule from the system manufacturer or installer. A typical LPG service involves:

• Leak check of the tank fittings, fuel lines, unions and converter.
• Gas filters inspected or replaced, as these trap contaminants before they reach the converter and injectors.
• Converter/regulator checked for correct operation, coolant leaks and signs of internal wear.
• Coolant hoses feeding the converter, since a weak coolant supply affects vaporisation.
• Lock-off solenoids checked to confirm they open and shut properly.
• Tank, mountings and valves checked for security, corrosion and damage, along with the tank’s last inspection stamp.
• Tuning and diagnostics on systems that support it, to confirm the engine is running correctly on gas.
• Ignition system (spark plugs and leads or coils) checked for condition.

The engine’s standard servicing still applies: oil, filters, coolant, belts, brakes and so on. A logbook service covers the petrol side; the LPG check is done alongside it.

Common LPG faults

Smell of gas

If you smell gas in or around the car, don’t ignore it. Switch off the engine, avoid any ignition sources, and have the system checked before driving on gas again.

Hard starting, stalling or poor idle on gas

Often linked to blocked filters, converter problems, a faulty lock-off, or ignition components that are getting tired. On injected systems, sticking gas injectors are another possibility.

Car won’t switch to gas, or keeps switching back to petrol

Changeover is usually controlled by coolant temperature and system sensors. A fault in the sensor, wiring, switch or gas ECU can stop the changeover. Low tank level or an issue at the tank valve can do it too.

Loss of power or higher gas use

Can come from filters, converter wear, tuning, ignition faults or a mechanical issue in the engine itself. Proper engine diagnostics separates gas-system faults from engine faults.

Backfire on gas

Usually points to an ignition or mixture problem. Have it checked promptly.

Compliance and certificates in NSW

Who can work on LPG systems

NSW Fair Trading has a specific motor vehicle tradesperson category for LPG: a liquefied petroleum gas mechanic “installs or repairs liquefied petroleum gas (LPG) equipment in motor vehicles”, and needs a Certificate III in Automotive Alternative Fuel Technology (or a light or heavy vehicle mechanical qualification plus the specified LPG units) (NSW Fair Trading).

Installation standards and paperwork

Transport for NSW’s vehicle standards information on LPG-fuelled vehicles says installations must comply with the Standards Australia automotive LP gas code (AS/NZS 1425). On a new installation, the installer fits a compliance plate and gives the owner a completed Certificate of Compliance. After a conversion, you must notify Transport for NSW so the registration records can be amended (Transport for NSW VSI 14).

Keep the Certificate of Compliance with your car’s papers. It’s useful when selling the car and can be asked for during inspections.

LPG labels

The same guidance requires LPG-converted vehicles to display a red retroreflective “LPG” label on the front and rear number plates (Transport for NSW VSI 14). These labels help emergency services identify a gas-fuelled vehicle. If yours are faded or missing, replace them.

Tank inspection every ten years

Transport for NSW guidance states that LPG tanks must be inspected every ten years and stamped with the date of the last inspection, and recommends owners arrange the inspection before the ten years are up (Transport for NSW VSI 14). Check the date stamp on your tank, especially on an older car or one you’ve just bought.

Pink slips for LPG vehicles

An LPG vehicle needs a yearly safety inspection (pink slip) once it is more than 5 years old, like any other light vehicle (Transport for NSW). Gas-powered vehicles are inspected by examiners who hold Transport for NSW authorisation to inspect them; to apply, an examiner must hold a NSW Fair Trading LPG and/or CNG mechanic tradesperson certificate (Transport for NSW). See when does my car need a pink slip? for the timing rules.

When to get your LPG system inspected

• At each scheduled service, as set by your gas system’s maker or installer.
• Whenever you smell gas, or the car runs poorly on gas but fine on petrol.
• When the tank’s ten-year inspection date is approaching.
• Before buying a used LPG or dual-fuel car.
• Before your pink slip, so any gas-system issues are fixed in advance.

LPG servicing in Kings Park

Andrew’s Mechanical services and repairs LPG and dual-fuel vehicles at 3 Goulburn St, Kings Park, alongside general servicing and pink slip inspections. See our LPG services page for more.