What Causes a Car to Fail to Start on Rainy Days?
2 Answers
On rainy days, a car failing to start is usually due to short circuits caused by damp electrical circuits. Here are other reasons why a car might not start: 1. Carbon buildup in the engine: If the car idles with slight shaking, cleaning the throttle body and fuel injectors can resolve the issue. 2. Weak spark plug ignition: If spark plugs are not replaced after their maintenance cycle, their ignition energy weakens, leading to misfires in severe cases. 3. Insufficient fuel pressure: Low pressure in the fuel system can cause the engine to require a second ignition. Check components such as the fuel pressure regulator, fuel pump, fuel filter, and internal fuel lines. 4. Dead battery: In this case, jump-starting the car with another vehicle or battery is necessary.
I've encountered this situation several times. That morning when I was driving in the rain, the car just wouldn't start. Most of the time, it's because the ignition system got wet—for instance, moisture seeping into the high-voltage wires, causing electrical leakage or spark plug short circuits. The battery is also a major issue, especially in older cars. The humidity on rainy days can cause the already weak battery voltage to drop further. Then there are the wire connectors under the hood—excess moisture can lead to corrosion and poor contact, and the starter motor is prone to rusting and malfunctioning. I recommend checking the distributor cap first to ensure it's properly sealed. I remember a mechanic once told me it's best to clean the battery terminals before rainy days to avoid dirt buildup. A more complicated issue is when the ECU circuit board gets damp—that requires towing for professional handling, so parking in an underground garage regularly can help. In short, if the car won't start, don't keep cranking the key; wait for sunny weather to let it dry out and try again.
