Starting the car in winter morning has a strong smell of gasoline. What's wrong with it?

It is normal that the exhaust pipe of a car will have a strong smell of gasoline after a cold start. Today, let's talk about the reasons for this, so that all car owners can feel at ease.

do you know how gasoline burns in the cylinder?

If you fill a cup with gasoline and light it with a lighter, you will find that the flame only burns on the surface of the gasoline, and the gasoline under the cup will not burn. In fact, it is not liquid gasoline that burns, but gasoline that evaporates into gas.

by the same token, gasoline should be evaporated after entering the cylinder and fully mixed with air to form a combustible gas with sufficient concentration before being ignited by the spark plug. If the gasoline is still liquid after entering the cylinder, the spark plug can't be ignited.

inject more fuel during cold start

We all know that the engine calculates the fuel injection quantity according to the intake air quantity combined with the theoretical air-fuel ratio. For example, if the engine inhales 14.7 grams of air and the air-fuel ratio is 14.7, then the fuel nozzle will spray 1 gram of gasoline. In this way, after the gasoline is completely volatilized, it just forms a mixture with an appropriate concentration with air.

However, the volatility of gasoline decreases with the decrease of temperature. For example, when the engine is cold-started, it still inhales 14.7 grams of air. If the fuel injector still sprays 1 gram of gasoline at an air-fuel ratio of 14.7, this 1 gram of gasoline may not be completely evaporated due to the volatility deterioration. If half of it is evaporated, the remaining half is liquid gasoline. In this way, the actual mixture concentration is reduced, and the spark plug is not easy to ignite.

Therefore, during cold start, the engine has enrichment control, and more oil is injected according to the actual temperature. For example, if the engine inhales 14.7 grams of air, then we have to provide 1 gram of gasoline vapor, but the evaporation of gasoline at the current temperature is only 1%, which means that only .1 gram of gasoline can evaporate when you spray 1 gram, and the rest is still liquid gasoline. So what should we do? Only 1 grams of gasoline can be sprayed, so 1% evaporation is just enough.

Thus, the tail gas naturally smells of gasoline.

During the cold start, 14.7 grams of air entered the cylinder, and 1 grams of gasoline was sprayed, of which only 1 gram of gasoline evaporated and mixed with air to participate in the combustion. The remaining 9 grams of gasoline still exists in the cylinder in liquid state. When burning in the cylinder, these liquid gasoline will be oxidized and carbonized at high temperature, but it can't be completely burned. So it was ejected from the exhaust pipe with the exhaust gas. So we smelled the obvious smell of gasoline. It's winter now. If you pay attention when you start the engine in the morning, you will find that the exhaust gas has a strong smell of gasoline. It doesn't matter. Generally, there will be a smell for a while at the moment of start-up, and it will be less obvious after a while.

If the engine can still smell gasoline after reaching the normal operating temperature, there is a problem. First, check whether there is leakage in the fuel system, because many interfaces of the fuel system are rubber pipes, which will become hard in winter, and the vibration when starting the engine will easily lead to its loosening, thus causing gasoline leakage.

If there is no leakage in the fuel system, it is basically something wrong with the engine itself. Generally, this kind of problem will be accompanied by the lighting of the engine fault light, so it is necessary to connect the computer to find the fault information before handling it.

This article comes from the author of Chejia, car home, and does not represent car home's standpoint.