Condensed water appears on the inner surfaces of the fuel tank when a car is parked in a warm space indoor with a small amount of fuel in the tank. The lesser fuel is in the tank and the bigger is temperature difference, the lager amount of moisture is condensed in the tank. Also water may get into the tank while fueling.

Water gradually mixes with fuel which leads to malfunction of the fuel pump and glow plugs. Diesel and injector engines encounter this problem more frequently. Condensed water leads to freezing of fuel hose and main filter of diesel engines in winter.

Unstable operation of the engine: revolutions will be inconstant, the engine operation will be jerky, especially on the rough road with not full fuel tank.

It is possible to remove water from the fuel tank and fuel system on the whole applying special agents for removing water from the fuel tank.