Topics:
- Backfire
- Causes
- Consequences
Backfire:
A backfire occurs due to a technical malfunction in a petrol engine, often one equipped with an (older G1 or G2) LPG system. A backfire is the term for the fuel igniting at the wrong moment, for example when it is still in the intake manifold. When the spark plug has not ignited the fuel, an air-fuel mixture is still present while the piston has already completed the power stroke. This means there is unburned fuel in the cylinder, which then ignites later due to the high temperature. That moment can be when the intake valve is open, causing the fuel to ignite in the intake manifold.
A backfire can occur while driving, but also while the engine is idling, or even during starting. In modern engines with an advanced engine management system, backfires almost never occur anymore, if at all. A backfire should not be confused with “pinging“.
Causes:
- Incorrectly adjusted ignition: The spark plug cannot ignite the mixture in time, because it produces a spark either too early or too late.
- Too lean mixture: The ratio between air and fuel is not correct; there is relatively too little fuel present to be ignited.
- Contaminated / carbon-fouled spark plug: Due to incorrect driving style, or postponing maintenance for too long, the spark plug is in too poor a condition to achieve optimal combustion.
- Defective spark plug wires: The spark from the spark plug is not correct.
- Converter: Due to a contaminated diaphragm in the converter of a gas system, it can happen that the gas supply does not stop in time. Gas is then still being supplied at undesirable moments, which can ignite in the intake manifold at high temperatures. (For clarification: the converter ensures that a gas mixture is made from liquid gas.)
Consequences:
Because the mixture has ignited in the intake manifold, a very high pressure has been present. Due to this explosion, the intake manifold may have cracked or blown apart. In addition, the air intake duct, the mass air flow or air quantity sensor, and the air filter including the air filter housing can be severely damaged or destroyed.