A further advantage of the preferred injector construction and operation is the ability to automatically prime the injector for a subsequent operation. By closing the external governor means, there is a hydraulic lock up of the low pressure side, and fuel will be stored in the delivery chamber 65 since the fuel cannot be released through the orifice 68 or through the delivery valve 56. Thus, when the associated engine is to be re-started, the first compression cycle of the associated engine will enable fuel under pressure in the delivery chamber 65 to be injected for commencing normal operation of the engine.

In the particular construction of injectors shown in the drawings, metal to metal contacts are used to provide sealing between immovable parts. For example, the front body 11 and rear body 13 are connected together with metal to metal contact between a sharp step 96 provided on the rear body 13 and a chamfered face 97 provided on the front body 11. This also applies to connections between the spacer 67 and the low pressure piston 30, between the spacer 67 and the high pressure piston 35, and between the high pressure barrel 44 and the base section 43. These connections are modified "Lenz ring seats" and provide good sealing under high pressures.

The valves, including the inlet valve 16, outlet valve 21, non-return valve 46, delivery valve 56 and the needle valve 70 preferably have sealing contact between the valve members and associated seats with an internal angle less than 90.degree., and preferably at about 60.degree.. For example, the included angle in the point of the needle valve 70 is preferably about 60.degree.. This relatively shallow angle of seating has been found to provide good sealing at a wide range of fluid pressures.