A backfire occurs in the event of a technical defect in a petrol engine, which is often equipped with an (older G1 or G2 -) LPG installation. A backfire is the name for igniting the fuel at the wrong time, for example when it is still in the intake manifold. If the spark plug has not ignited the fuel, there is still an air-fuel mixture present, while the piston has already made the power stroke. There is therefore unburned fuel in the cylinder, which will be ignited at another time due to the high temperature. That moment can be when the intake valve is open, igniting the fuel in the intake manifold.
A backfire can occur while driving, but also when the engine is idling, or even during starting. In modern engines with an extensive engine management system, backfires are rare or not at all. A backfire should not be confused with “ping".
- Misadjusted ignition: The spark plug cannot ignite the mixture in time because it sparks too early or too late.
- Mixture too lean: The ratio of air to fuel is not right; there is relatively little fuel available to ignite
- Dirty / charred spark plug: Due to incorrect driving style, or too long postponing maintenance, the spark plug is in too bad a condition to achieve optimal combustion.
- Faulty spark plug wires: The spark of the spark plug is faulty.
- Convector: Through a contaminated membrane in the convector of a gas installation, the gas supply may not stop in time. Gas is then added at undesired moments, which can then ignite in the intake manifold at high temperatures. (To be clear, the convector ensures that a gas mixture is made from liquefied gas.
Because the mixture ignited in the intake manifold, there was a very high pressure. This explosion could cause the intake manifold to crack or collapse. Furthermore, the air intake pipe, the air mass or air flow meter and the air filter including the air filter housing may be badly damaged or broken.