When people hear "LPG service," many picture a quick filter swap and nothing more. At some shops, that really is all you get. But a proper LPG service covers six serious steps, and each one exists for a reason. On this page we walk through exactly what happens in our workshop and why every step matters. If you want to know how often to schedule a service and at what mileage, we covered that in detail in our guide on LPG service intervals.
Liquid-phase and vapor-phase filter replacement
Every LPG system has at least two filters. The liquid-phase filter sits between the tank and the reducer, catching mechanical debris, oil residue, and particles that come from the fuel itself at the pump. When it clogs, the reducer starves for fuel and the engine loses power, especially under load.
The vapor-phase filter sits after the reducer and before the injectors. It protects the precision internals of the injectors from fine particles generated inside the reducer during evaporation. A clogged vapor-phase filter restricts gas flow and creates a lean mixture, which means hesitation, higher consumption, and the risk of overheating the valves.
Both filters get replaced at every service, no exceptions. When we pull the old one, a single glance usually tells the story. A filter that went in white and comes out grey or black speaks for itself.
Full-system leak inspection
This is the safety check that never gets skipped. We use an electronic gas detector and foaming spray to go over every connection in the system. That includes the fittings on the tank and multivalve, the reducer connections, every hose clamp, the injector rail joints, and the intake manifold fittings.
Gas leaks often cannot be detected by smell because the concentration is too low, but the detector picks up even the smallest seepage. Rubber hoses harden and lose elasticity over time, clamps loosen, and micro-cracks develop at joints. We pay extra attention on vehicles where the LPG system has been installed for more than five years. Any problem we find gets resolved on the spot, before we move on.
Reducer and evaporator, membrane and condensate
The reducer is the heart of the LPG system. It converts liquid gas into vapor using heat from the engine coolant. We check the membrane condition, the gaskets, and the outlet pressure setting. A reducer that does not hold proper pressure sends too much or too little gas, directly affecting the mixture, consumption, and combustion temperature.
At every service we drain the condensate from the reducer. This is an oily residue that accumulates inside the chamber during normal operation. If left undrained, it reduces chamber volume and interferes with membrane movement. On higher-mileage vehicles, the reducer sometimes needs an overhaul, replacing the membrane and the full gasket set. It is a straightforward job that can noticeably improve how the entire system performs.
LPG injectors, flow rates and response times
LPG injectors must open and close with sub-millisecond precision. Any deviation in response time means one cylinder gets more or less gas than the others, causing uneven engine operation.
During the service we measure flow rate and response time on each injector individually and compare against factory specifications. If any injector falls outside tolerance, we remove it for cleaning. After cleaning we measure again. If the results still fall short, we recommend replacement. Our guide on common LPG problems explains in more detail what happens when injectors start to fail.
Calibration, diagnostics, and test drive
This is the step that separates a thorough service from a superficial one. We connect a diagnostic laptop to the LPG controller and read parameters in real time. We look at fuel trim corrections on the petrol side, both short-term and long-term, and then on the gas side. The goal is for the LPG system to operate within a narrow correction window, similar to the engine running on petrol.
We adjust the electronic maps per cylinder, fine-tune the initial injection point, the transition parameters between petrol and gas, and the response across different RPM ranges. Poorly tuned maps result in either excessive consumption or a dangerously lean mixture that can damage the valves. Every LPG system manufacturer, whether Stag, Lovato, Zavoli, or AC, has its own software and its own tuning characteristics.
The service does not end at the laptop. After calibration we take the car for a test drive, observe engine behavior under real-world load and across different RPM ranges, then come back for final adjustments if needed.
Tank, multivalve, and what a sloppy service skips
The tank is a component many people forget because it is hidden in the boot or under the car. We check the mounting brackets and hardware, look for surface corrosion and corrosion at connection points, and verify multivalve operation. The multivalve controls filling and discharge, and its safety valves must be fully functional.
LPG tanks in Bosnia and Herzegovina are subject to periodic inspection and certification. During the service we check the certification date and let the driver know if the renewal deadline is approaching. Do not neglect the tank just because it is out of sight. Corrosion and damage develop silently and can become a serious issue.
A sloppy service means swapping filters and maybe glancing at the injectors. No leak check, no condensate drain, no diagnostics, no calibration. The engine might run after a service like that, but it runs on old maps that no longer match the actual state of the components. The result is higher consumption, rougher engine behavior, and a shorter system lifespan.
If you notice that your car still consumes more than it should after a service, or that the engine does not run smoothly, the calibration may not have been done properly. We wrote more about symptoms that point to LPG system issues in our guide on poor engine performance on gas.
At our workshop, every LPG service goes through all the steps described above, from filters to the test drive. If you would like to book a service or have questions, visit our LPG service Banja Luka page or contact us directly through our booking page.