Water in the fuel (contamination) reduces combustion heat in the cylinder which can cause;

1. Smoke
2. Harder to Start
3. Less

   Water also has detrimental effects on the fuel system components including the fuel injection pump, injectors, fuel filter housings etc. The water causes corrosion, especially on the highly polished precision parts in the fuel injection pump and injectors.

   The water contamination has an effect on the fuel filter element which rots because of the water and the microbes that breed, eventually the filter will break up (rot) and these particles will cause damage to your fuel injection system and the probable outcome will be a very expensive fuel system failure.

   In the winter other problems can occur if the temperature drops below freezing, for example;

   1. Water freezing can cause ice crystals in the fuel system and cause the diesel to emulsify (or gel).
   2. Water in the fuel system and indeed Bio diesel users who have heated filters or lines, have a greater chance of having microbe problems. Many people use a Fuel System cleaner like the Diesel Jones Fuel System Cleaner to eradicate small contamination and microbe problems.
   3. In severe cases water contamination can cause pitting on the pistons of the engine.

   It may not be very realistic but with a lot of the fuel returning to the tank the fuel tends to get warm so when you stop the engine and leave it parked for a length of time condensation forms in between the top of the tank and the diesel.

   The water droplets can drip off the top of the tank and then this is where some water enters your fuel system which accelerates the growth of microbes because of the water and temperature inside the tank.

   This is more of a problem in stationary engine and canal boat engines where diesel quality may not be as good and is not as readily available as it is for road going vehicles.

   This problem does not only exist on just diesel engines, it also effects diesel heating systems that are fitted to vehicles such as night heaters and canal barges, whose heating systems and hot water for washing and showering can be greatly affected.

   As a preventative measure, the fuel filters should be cleaned and personally I think water traps should be fitted to try and prevent water from getting into fuel injection and heating systems. If one is fitted and you should regularly check to see if there is any water in the system it is also a good indication of how regular you should change your fuel filter.

   Because it is not cheap to change a good quality fuel filter, if you find that there is no water or signs of contamination in the water trap you can maybe change the filter less frequently than if it is contaminated. But at the end of the day if you have any doubts change the filter because it is a lot cheaper than repairing your fuel pump and injectors. It is also a lot cheaper than repairing your night heater or heating and hot water system