An LPG system on a vehicle runs reliably as long as it gets regular maintenance. When it doesn't, problems creep in gradually, and drivers often fail to connect jerking or higher consumption with a missed service. Here we'll go through every item covered by an LPG service, the intervals for each one, and why the condition of the petrol side directly determines how the gas system performs.
Phase Filters: Liquid and Vapour
Every LPG system has two filters. One sits in the liquid phase (between the tank and the vaporizer) and catches larger impurities from the liquid gas. The other sits in the vapour phase (between the vaporizer and the injectors) and catches finer particles that passed through the vaporizer. Both are consumable and must be replaced regularly.
The replacement interval depends on gas quality at the pumps and how much you drive. As a guideline, filters are changed every 10,000-15,000 km or once a year, whichever comes first. Drivers who fill up at various stations or cover higher annual mileage sit closer to the lower end. Those who always fill at the same pump and drive less can stretch toward the upper end, but even then the yearly change should not be skipped.
A clogged filter restricts gas flow, the mixture goes lean, and the engine responds with jerking, power loss and an unstable idle. If you're experiencing this, filters are always the first place to look.
Gas Injectors and Map Calibration
LPG injectors perform millions of opening and closing cycles. Over time, deposits build up, sealing elements wear and springs weaken. The result is imprecise gas dosing that usually doesn't manifest evenly: one cylinder gets too much, another too little, giving the engine a characteristic uneven jerk.
Injectors are typically serviced with ultrasonic cleaning at 80,000-100,000 km, and full replacement comes due at 150,000-200,000 km depending on the system type and maintenance quality. During a regular LPG service, the flow and response time of each injector are checked, so problems get caught before they become faults.
Alongside the injectors comes electronic map calibration. Maps control the amount and timing of gas injection, and they were set for the engine's condition at the time of installation or last adjustment. As spark plugs wear, coils weaken and compression dips slightly, the maps no longer match the actual state. Recalibrating at every service is five minutes of work that keeps consumption within normal range.
Vaporizer: Diaphragm, Pressure and Overhaul
The vaporizer (reducer) converts liquid gas into vapour form. To work correctly, it needs proper operating pressure, a healthy diaphragm and enough heat from the engine coolant. The diaphragm regulates flow and pressure, and it is made of rubber or silicone that loses elasticity over time.
When the diaphragm weakens or cracks, the output pressure from the vaporizer becomes unstable. The typical symptom is poor running on gas until the engine warms up (especially in winter), power loss under load, or the system spontaneously switching back to petrol. On larger-displacement engines (1.8 and above), an undersized vaporizer that cannot supply enough gas at full throttle is a common issue as well.
Condition is checked by measuring outlet pressure under load. If it's out of spec, the repair is usually a diaphragm and seal kit replacement, which brings the vaporizer back to factory operation. A full overhaul is typically done at 100,000-150,000 km, depending on component quality and how regularly the rest of the system has been serviced.
Hoses, Connections and Leak Checks
All gas lines from the tank to the vaporizer and from the vaporizer to the injectors have hoses and fittings that age. Rubber dries out and cracks over time, metal fittings oxidise, and clamps work loose. A visual inspection of all lines and connections at every service is mandatory, because even a small leak that's barely noticeable at first glance can upset system pressure and cause unstable running.
The smell of gas in the engine bay or around the tank in the boot is a signal for an urgent check. LPG systems have built-in safety valves, but relying solely on them is not recommended practice. Regular connection inspections catch problems while they're still minor.
The Petrol Side That Directly Affects Gas
This is the item drivers overlook most often. Spark plugs and ignition coils affect gas operation far more than petrol operation. The reason is physical: the gas mixture requires a stronger spark to ignite than the petrol mixture. When a plug is worn or a coil has weakened, the spark is strong enough for petrol but not strong enough for gas.
The result is a car that runs normally on petrol but jerks, misfires and consumes more on gas. Many drivers conclude at that point that the gas system is at fault, when in reality a spark plug change would fix things. More detail on this pattern and the order of checks can be found in the guide to poor running on LPG.
That is why every spark plug or coil replacement is always followed by a gas map recalibration. Old maps tuned for worn plugs don't match the new state, so the car can jerk on gas even though the petrol side is now correct.
Signs That LPG Service Is Overdue
Some symptoms clearly tell you the service interval has long passed:
- Jerking on gas during steady driving, especially at lower RPM.
- Delayed switchover from petrol to gas, or the car staying on petrol longer than usual.
- Noticeably higher gas consumption compared to before.
- The engine briefly stumbles or shudders when switching to gas.
- Gas smell in the engine bay or boot.
Each of these symptoms has a specific cause in one of the items described above. An overview of the most common LPG problems covers diagnostics step by step. The key is not to ignore them, because every delay increases the chance of a minor issue growing into a more expensive repair.
As for certification and paperwork, the LPG tank has a periodic inspection that is carried out a set number of years after installation, depending on the tank type. The inspection confirms the tank is still safe to use. Details on regulations and deadlines are best discussed during a service, as they depend on the specific installation.
If you haven't had your LPG system serviced in the last year or recognise any of the above, don't put it off. Book an appointment and we'll go through the complete gas system.