Abstract: An improved apparatus for cleaning internal combustion engines by providing a cart with wheels to transport the apparatus to the engine to the serviced. The apparatus can contain a battery or be connected to the power supply of the engine. A cleaning solution is poured into the reservoir of the apparatus. A pump delivers the cleaning solution to the input junction of the fuel supply line of the engine. Control switches insure the apparatus is started and brought up to operating pressure. If internal pressure is not achieved or if pressure is lost during operating, the power to the pump is interrupted. A return line is provided to establish a pathway for excess cleaning solution to be returned to the reservoir of the apparatus. The return line incorporates an adjustable pressure regulator to compensate for an inadequate or manufactioning engine fuel pressure regulator.