How to Deal with Gasoline Smell in Exhaust During Cold Start?

[LeviRose]

This is a normal phenomenon, as all vehicles emit a gasoline smell during cold starts. The gasoline odor is related to the control method of the injection system, which operates in two modes: 1. Open-loop control and closed-loop control. During open-loop control, the system does not reference data from the oxygen sensor. For a period after the vehicle starts, the engine injection system operates under open-loop control. The high concentration of the air-fuel mixture results in unburned gasoline being expelled with the exhaust, which is why there is a gasoline smell in the exhaust. 2. After increasing the fuel injection, some gasoline cannot be completely burned and is expelled through the exhaust system. Therefore, there is no need to worry about the gasoline smell from the exhaust pipe during a cold start. The odor will disappear as the engine temperature rises.

[SanCamilla]

I encountered this situation when helping a friend fix his car last time. It's actually quite common to smell gasoline during a cold start, mainly because the engine temperature hasn't risen enough, leading to incomplete fuel combustion. However, if the smell is particularly strong or lasts for a long time, you should be cautious. I recommend first checking the fuel pump seal ring, as that's the most common spot for gasoline vapor leaks. Next, see if the carbon canister purge valve is stuck in the open position. Loose fuel line connections can also cause leaks, especially for cars over five years old—those pipe joints should be thoroughly inspected. If the smell doesn't dissipate after the engine warms up for ten minutes, immediately check the oxygen sensor and fuel injector atomization. The easiest solution is to take it to a repair shop for a smoke test—just a couple hundred bucks can pinpoint all the leak points.

[MaciLee]

My old car always has this issue in winter, emitting a strong gasoline smell during cold starts. The mechanic suggested I first check the exhaust pipe. If there's black smoke along with the gasoline smell, it's likely due to an overly rich air-fuel mixture. The focus should be on inspecting the carbon canister system, especially since saturated gasoline adsorption in the activated carbon canister can lead to vapor leaks. Aging seals on the fuel injectors can also cause gasoline leakage, particularly in turbocharged models where higher pressure makes them more prone to issues. A faulty intake pressure sensor can mislead the ECU into miscalculating fuel injection, so it's also worth checking if the mass airflow sensor data is abnormal. Regular maintenance with fuel system cleaners is essential; it's best to add a bottle every 5,000 kilometers. For older cars, replacing rubber fuel hoses with oil-resistant and high-temperature-resistant materials is highly recommended.

[MacFrank]

Just dealt with the same issue—strong gasoline smell during cold starts is mostly a combustion problem. First, check if the smell disappears after the engine warms up. If the odor persists when the engine is warm, repairs are urgent. Focus on three key areas: 1) The fuel pump flange sealing ring may be aged or cracked, leaking gasoline vapors. 2) The fuel tank cap seal could be deformed, also causing leaks. It’s best to remove the fuel pump and check if the fuel level float is stuck. 3) For injector drip, test the injection pulse width balance across all four cylinders. Spark plug condition also affects combustion efficiency—replace them if the electrodes are excessively worn. Don’t overlook aging engine wiring harnesses; damaged wires can spark and ignite gasoline vapors, which is dangerous. Small issues left unfixed can escalate into major problems.