Fuel injector

A fuel injector (1) for injection of fuel at high pressure into a cylinder in an internal combustion engine, comprising a first pressure chamber (7) located at a valve seat (9), a main spindle (10) which, in a closed position, abuts the valve seat and cuts the fuel off from access from the first pressure chamber to atomizer nozzles and, in an open position, is displaced away from the valve seat and permits injection of fuel, a second pressure chamber (14) located separately from the first pressure chamber and containing a first opening area (OA) (15) on the main spindle, a third pressure chamber (17) containing a closing area on the main spindle (10), and a pilot spool (24) that, via a flow passage, can connect a high-pressure port with the second pressure chamber, characterized in that in a first position the pilot spool connects the high-pressure port (20) with the second pressure chamber (14) and a low-pressure port (51) with the third pressure chamber (17), whereby the main spindle is in its open position, and that in a second position the pilot spool (24) connects the low-pressure port with the flow passage to the second pressure chamber (14) and the high-pressure port with the third pressure chamber (17), whereby the main spindle is in its closed position.