A fuel tank is a part of an engine system in which the fuel is stored and propelled (fuel pump) into the engine. Fuel tanks range in size and design according to the car model. Fuel may contain water or impurities which affect the tank material and/or piping system (corrosion, clogging, wear of seizure of precision parts) and in some cases the burning process. There are many different methods and materials used to wash and clean engine fuel tanks. Unfortunately these methods depend on removing the tank from the car in a process takes not less than three hours from a professional person. This paper introduces a new simple method to clean the fuel tank while it is in place without taking the tank out of the car. The idea depends on timed steps to inject different safe washing fluids using a specially designed nozzle and remove them after washing in a total period of time of 15 minutes. The system was tested on a rusted fuel tank filled with gasoline which had a high degree of impurities and the obtained result in the designed time was challenging.