A situation where the car refuses to switch to 4th generation gas fuel is familiar to many owners of vehicles equipped with LPG. Most often, the system operates without complaints, but at a certain moment the vehicle continues to move exclusively on petrol, ignoring the command to switch. In this material, we will examine in detail why the car does not switch from petrol to gas, highlight the most common causes, and offer an action algorithm for quickly fixing the malfunction.

1. How 4th generation LPG works

Before looking for the source of the problem, it is necessary to understand the operating principles of 4th generation gas equipment. The system design includes several key components:
  • fuel tank filled with propane-butane or methane;
  • evaporator reducer responsible for converting gas from liquid to vapor phase;
  • gas injectors through which fuel enters the engine;
  • a set of sensors monitoring temperature, pressure, and crankshaft speed;
  • electronic control unit (ECU) managing the moment of fuel type change.
In normal mode, automatic switching occurs after the engine warms up to 30-40 °C. If the temperature is below this threshold, the system continues to run on petrol. This is done to protect the reducer from freezing and prevent malfunctions in the gas equipment operation.

2. Main reasons for refusing to switch to gas

2.1. Insufficient warming up of the power unit or reducer

The most common reason why the car does not switch to 4th generation gas lies in insufficient temperature of the engine or reducer. Why this happens:
  • in cold weather, the engine does not warm up to the required 30-40 °C;
  • the temperature sensor has failed or transmits incorrect readings;
  • the thermostat is stuck in the open position, causing the coolant not to heat the reducer properly.
Recommendations for fixing:
  • let the engine warm up completely;
  • check the thermostat's functionality and replace it if necessary;
  • check the reducer temperature sensor — if it is faulty, the ECU will not allow switching to gas.

2.2. Empty gas cylinder

A trivial but very common reason — the tank simply ran out of fuel. In 4th generation systems, the electronics do not always correctly display the gas level, especially in cold weather. What to do:
  • fill the cylinder completely;
  • after refueling, restart the engine and wait for it to warm up.
Tip: do not fully rely on the gas level indicator — its data is approximate.

2.3. Malfunction of solenoid valves

The LPG design includes two solenoid valves: one is located on the cylinder, the other on the reducer. If at least one of them does not open, gas supply to the engine stops. Possible causes:
  • burnout of the valve winding;
  • broken wiring or weak contact;
  • sticking of the valve piston.
Solutions:
  • check if a characteristic click is heard when gas is activated (this indicates the valve is working);
  • test the coils with a multimeter (normal resistance — 10-16 Ohms);
  • if a fault is found, replace the valve.

2.4. Problems with the gas pressure sensor

When the pressure (or temperature) sensor transmits distorted data, the ECU prohibits switching to gas fuel. Symptoms of malfunction:
  • no switching to gas, the indicator blinks;
  • during diagnostics, a gas pressure error is displayed;
  • gas injectors do not activate.
What to do:
  • perform diagnostics using specialized LPG software (Stag, Lovato, BRC, etc.);
  • clean the sensor connector contacts and check the wiring integrity;
  • replace the sensor if it is non-functional.

2.5. Failure of the evaporator reducer

This component is responsible for converting gas into a working state and maintaining stable pressure. If the reducer is dirty or its membranes are worn, the car does not switch from petrol to gas. Causes of malfunction:
  • wear of membranes or valve group;
  • freezing of the reducer housing in winter;
  • oil or dirt entering the system.
Action plan:
  • perform service maintenance or repair of the reducer;
  • if freezing occurs — check the antifreeze circulation;
  • replace the coarse and fine filter elements.

2.6. Electronic failures and errors

Sometimes 4th generation gas does not activate due to a software glitch in the control unit. Factors causing the problem:
  • poor ground connection or power supply disruption to the ECU;
  • software error that occurred after reflashing;
  • failure during system adaptation.
Ways to fix:
  • reboot the system (disconnect LPG power for 1-2 minutes);
  • inspect fuses and relays;
  • if necessary, contact a specialist for diagnostics.

2.7. Freezing of fuel or moisture in the system

At sub-zero temperatures, condensation accumulation often occurs, which can block valve operation or clog filters. What can be done:
  • place the car in a heated garage;
  • let the system completely thaw and warm up;
  • replace filters if ice has formed or dirt has accumulated in them.

3. Step-by-step action plan when switching to gas fails

  1. Check the gas level in the cylinder.
  2. Warm up the engine to operating temperature.
  3. Listen — are there clicks from the solenoid valves when attempting to switch.
  4. Evaluate the readings of the indicators on the LPG panel.
  5. If self-checks do not help — connect the diagnostic cable and read error codes.
Do not forcibly switch the system manually if the ECU blocks the transition — this may cause damage to the reducer or injectors.

4. Preventive measures to avoid problems

  • Replace gas filters every 10-15 thousand km of mileage.
  • Perform annual maintenance of the reducer.
  • Try not to allow the cylinder to become completely empty.
  • In winter, refuel with a high-quality propane-butane mixture with a low evaporation threshold.
  • Regularly check the condition of wiring and contact connections.

Summary

If the car does not switch to 4th generation gas, the culprit may be insufficient warming up of the power unit, an empty tank, failure of valves, reducer, or sensors. In some cases, the problem lies in the electronics. Start diagnostics with simple checks: fuel level, temperature, valve operation. If the system does not respond to actions — contact a specialized service for in-depth diagnostics.