What Causes a Car Not to Start on Rainy Days?

[McGiselle]

If a car fails to start on rainy days, it is likely due to rust or leakage in the battery, or the engine spark plugs getting damp. The best solution is to move the car to a sunny spot when the weather is clear to evaporate any moisture in the corners. Here are some additional details: 1. Low Battery Voltage: In cold temperatures, the electrolyte viscosity in the battery increases, reducing its permeability and increasing resistance, which lowers the output power. This makes it difficult for the starter to crank the engine to the minimum starting speed, affecting engine ignition. Additionally, the weak spark from the spark plugs due to low battery voltage, combined with the increased resistance between electrodes caused by dense air-fuel mixture, makes it hard to ignite the mixture, further complicating engine startup. 2. Short Circuits or Clogged Fuel Lines: Since most of the vehicle's wiring and fuel lines are concentrated in the engine compartment, driving through water can cause these components to get wet. Over time, this may lead to short circuits in the wiring or clogged fuel lines, directly resulting in the car not starting. For vehicles that have been submerged in water, there may be even more issues. Even after drying the engine compartment, attempting to start the engine still carries some risk.

[Javier]

I remember one rainy day when my car wouldn't start either. After struggling for a long time, I finally realized it was because the ignition system got wet—rainwater had seeped into the wire connectors, causing a short circuit or oxidation. Check under the hood; wire connectors and battery terminals are prone to rust and corrosion, especially in older cars. If the spark plugs or ignition coils get wet, they can also prevent the car from starting. The solution is to wipe the connectors with a dry cloth, spray some rust inhibitor, and try again after the rain stops and everything dries out. Avoid repeatedly attempting to start the car, as it can damage the starter. I learned my lesson—now I always try to park in dry spots, maintain the electrical system regularly, and avoid similar troubles. When the weather is bad, I leave extra buffer time before heading out.

[Ralph]

When working on car repairs, I often encounter this situation—cars not starting in rainy weather are mostly due to moisture. Rainwater may seep into the electrical system, causing short circuits or oxidation of wiring, which can affect the ignition coil and spark plugs. Accelerated corrosion of battery terminals can also lead to power supply interruptions. Check for loose or rusty wires and connections; sometimes a simple cleaning can fix the issue. A damp starter can also cause stalling. It's advisable to use waterproof tape to protect critical components as a preventive measure. Don’t overlook the impact of the wiper system linkage, and be extra cautious during heavy rain. Afterward, a comprehensive inspection by a professional shop is recommended for added safety. Keeping the car dry is key for long-term prevention.

[MaddoxLynn]

Last time it rained in the morning, I couldn't start my car when rushing to catch the shuttle bus - it was so frustrating! A friend reminded me it might be an electrical circuit issue, as rainwater can cause wires to short-circuit or oxidize due to moisture. A damp ignition system will fail. Quickly check the battery terminals - if there's corrosion, wipe it clean. If that doesn't work, don't force it to avoid further damage. Waiting for the rain to stop and letting things dry might solve the problem. When parking normally, avoid waterlogged areas. On rainy days, start the car early for inspection to avoid embarrassing lateness. Asking for help or calling a tow truck are also options. Safety first!