The disclosure of U.S. patent application Ser. No. 11/161,914 including the specification, drawings and abstract is incorporated herein by reference in its entirely. An improved pilot-operated, “instant-on”, solenoid isolation valve discloses a new fluid passage route to save cost of drilling a longitudinal hole within the primary piston. Also, a new feature of primary piston assembly with a movable seal piston having a specific circumferential surface matching to valve body chamber to restrict fluid from front side into back side of the primary piston to produce pressure difference to induce instant valve open when solenoid is energized initially. It also introduces a channel hole in the flange of the sleeve assembly as a communication channel of supply of gas into the chambers of the back side of primary piston assembly. The diameter of the channel hole is not critical to determine in this new invent. As long as the size of the hole is smaller than that of the bleed hole, it can maintain pressure difference between the front side and back side of primary piston during valve opening operation. In addition, since the pilot piston and the primary piston assembly operate independently, the travel stroke of the primary piston assembly is unconstrained by the input electrical power.