Fuel Injector Operation High-pressure fuel is supplied from the Bosch VP44 injection pump, through a high-pressure fuel line, through a steel connector, and into the fuel injector. When fuel pressure rises to approximately 31,026 kPa (4,500 psi), the needle valve spring tension is overcome. The needle valve rises and fuel flows through the spray holes in the injector nozzle tip into the combustion chamber. The pressure required to lift the needle valve