How to Determine if the Charcoal Canister Solenoid Valve is Good or Bad?
3 Answers
Methods to determine the condition of the charcoal canister solenoid valve are as follows: 1. Disconnect the plug of the charcoal canister solenoid valve. If the suction phenomenon stops, it indicates the solenoid valve is working properly; if suction continues, it means the solenoid valve is damaged. 2. The activated carbon has an adsorption function. When the car is running or turned off, gasoline vapor from the fuel tank enters the upper part of the activated charcoal canister through the pipeline, while fresh air enters from the lower part of the activated charcoal canister. 3. After the engine is turned off, gasoline vapor mixes with fresh air inside the canister and is stored in the activated charcoal canister. When the engine is started, the solenoid valve of the fuel evaporation purification device, installed between the activated charcoal canister and the intake manifold, opens, and the gasoline vapor in the activated charcoal canister is sucked into the intake pipe to participate in combustion.
Last time my car had unstable idle speed and a gasoline smell, and it turned out to be a faulty carbon canister purge solenoid valve. In fact, it's quite simple to diagnose: after the engine warms up, listen closely near the solenoid valve during idle - it should make a regular ticking sound. If there's no sound at all or the noise is irregular, there's definitely a problem. I've tried unplugging it and blowing air into the intake pipe when powered - if air passes through, it's good; if not, it needs replacement. Overfilling the fuel tank can also clog the solenoid valve, so I recommend not filling beyond the automatic pump shut-off. When this part fails, it can increase fuel consumption. While repairs aren't expensive, don't attempt to disassemble components near the fuel tank yourself to avoid potential hazards.
I often use these three methods when repairing cars: First, listen to the working sound of the solenoid valve. Open the engine cover and locate the square valve body near the charcoal canister. It should produce a steady clicking sound at idle; silence indicates it's not working. Second, remove the hose and perform a blowing test. Normally, it should allow airflow only when powered on and block airflow when powered off. If it's always open, the valve might be stuck in the open position, causing a rich air-fuel mixture. Third, measure the resistance. Use a multimeter set to the ohms range to measure across the coil terminals. A reading between 20-30 ohms is considered normal. Note that air leaks can cause hard starts and a surge in fuel consumption. Regularly cleaning the charcoal canister's dust layer can also extend the solenoid valve's lifespan.
