* Condensation: This is the most common cause, especially in areas with fluctuating temperatures. Moisture in the air condenses in the fuel tank, fuel lines, and filters, particularly if the tank isn't full. Cold temperatures exacerbate this.
* Leaking Tank: A crack or hole in the fuel tank itself allows rainwater or ground water to enter directly. This is more likely with older, rusty tanks.
* Leaking Fuel Lines/Fittings: Damaged or poorly sealed fuel lines, connections, and filters can let water in.
* Faulty Fuel Cap: A loose or damaged fuel cap can allow water to enter the tank.
* Contaminated Fuel: The fuel itself may have been contaminated with water at the point of delivery or storage. This is more common with older or poorly maintained storage facilities.
* Water Ingress through the Fuel Filler: Poorly designed or damaged fuel filler necks can allow water to run down into the tank.
* Submerged Fuel Tank (flooding): If the vehicle is submerged in water (e.g., flood), water will inevitably enter the fuel tank.
The effects of water in diesel fuel can range from minor performance issues to catastrophic engine damage. Water doesn't burn and can cause corrosion, clog filters, and damage fuel injectors.
