Fuel injector

A fuel injector nozzle assembly 12 has a hollow body 14 extending along a longitudinal axis A and containing a valve member 16 slidably guided by means of a first sliding guide G1 and a second sliding guide G2. The valve member 16 is displaceable between an open position where a valve seat 58 is distant from a seating surface 40 enabling fuel injection through spray holes 34 and, a closed position where the valve seat 58 is in contact with the seating surface 40 preventing fuel injection. The valve seat 58, the seating surface 40 and the spray holes 34 are arranged between upper guide G1 and lower guide G2. The invention addresses the issue of upward thrust variations on the valve seat 58 of the valve member 16, due to different areas being exposed depending on if the valve is seated or not. This variation in upward, or opening, forces makes it difficult to control the valve member movements.