As a domain expert with a focus on fuel systems and their maintenance, I can provide a comprehensive explanation on how water can infiltrate a diesel fuel tank and the potential consequences of such an occurrence.
Water entering a diesel fuel tank is a common issue that can lead to a variety of problems for diesel engines. Here's a detailed look at the process and the factors involved:

### Condensation
Diesel fuel tanks are always subject to water condensation because diesel fuel, unlike gasoline, has no vapor pressure to displace air. When the fuel tank is warm, the air inside expands and is forced out. As the tank cools down, it contracts, drawing in outside air, which can be humid. This humid air, when it comes into contact with the cooler surfaces within the tank, can lead to condensation. Over time, this can result in a significant amount of water accumulation.

### Capillary Action
The diesel fuel system includes various components such as fuel lines, filters, and injectors, which have small openings.
Capillary action can draw water through these small openings and into the fuel system. This is particularly problematic because water does not combust like diesel fuel and can lead to poor engine performance or even damage.

### Fuel Quality and Contamination
The quality of the diesel fuel itself can be a factor. If the fuel is contaminated with water or other impurities from the source, it can introduce water into the tank upon refueling. Additionally, diesel fuel can absorb water if it is stored for a long period, especially if the storage conditions are not ideal.

### Tank Design and Materials
The design of the fuel tank and the materials used can also affect the propensity for water accumulation. Some tanks may have a design that is more prone to collecting water, especially if they do not have proper baffling to prevent water from mixing with the fuel.

### External Factors
Environmental factors such as heavy rainfall, flooding, or even the tank being submerged can lead to water entering the tank from the outside. Additionally, if the tank is not properly sealed, water can seep in through small cracks or gaps.

### Consequences of Water in Diesel Fuel
The presence of water in diesel fuel can have several negative effects on the engine:


1. Clogged Fuel Filters: Water can cause rust and other contaminants to form, which can quickly clog fuel filters, reducing fuel efficiency and potentially causing the engine to stall.


2. Engine Damage: Since water does not combust, it can cause a lack of power and may lead to serious engine damage over time.


3. Increased Emissions: Water in the fuel can also lead to increased emissions, which is not only bad for the environment but can also lead to legal issues if emissions standards are not met.


4. Cold Starting Issues: Water in the fuel can make it difficult for the engine to start in cold conditions, as water can freeze and block the fuel lines.

### Prevention and Remediation
To prevent water from entering the diesel fuel tank, it's important to:

- Regularly inspect and maintain the fuel tank and its components.
- Use high-quality diesel fuel from reputable sources.
- Ensure the tank is properly sealed and protected from environmental factors.
- Install a water separator or use a fuel/water separator if possible.

If water is found in the diesel fuel tank, it's crucial to remove it promptly. This can be done by:

- Manually draining the tank and replacing the fuel.
- Using a fuel additive that is designed to separate water from diesel.
- Employing a professional service to clean and dry the tank.

In conclusion, while water in a diesel fuel tank is a common issue, it's one that should be taken seriously due to the potential for significant engine damage and performance issues. Regular maintenance and careful fuel management are key to preventing this problem.

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Diesel fuel tanks are always subject to water condensation because diesel fuel, unlike gasoline, has no vapor pressure to displace air. When a fuel tank is warm, the air expands and is forced out. ... These rust particles can quickly clog fuel filters.Dec 5, 2013read more >>