and an inner cylindrical surface 47 forming a boundary of the interior space 48 of the spring cage assembled in the space 48 are a helical compression spring 51 a spring seat 52 at the lower end of the spring and a shim 53 at its upper end the spring seat 52 has a blind bore in which a reduced diameter stub of the needle valve fits at its upper side the spring seat 52 has a cylindrical shank 54 sized to fit into the inside diameter of the helical spring 51 when the spray tip 24 spring cage 23 and spacer 22 are held in place by the nozzle nut 26 the spring 51 is compressed to hold the needle valve 36 closed on the seat 39 with a predetermined force an annular chamber 56 formed between the nozzle nut 26 and body 16 receives pressurized fuel from the supply rail e g at about 105 psi this pressurized fuel communicates with an annular chamber 57 around the spacer through a flat 58 on a threaded area at the bottom of the housing 16 similarly flats 59 on diametrally opposite outer sides of the spacer communicate rail pressure fuel to the outer periphery of the spring cage 23 both the spray tip 24 and spacer 22 have outside diameters that produce a close fit with respective surrounding internal surfaces of the nozzle nut.