U.S. Pat. No. 4,394,856 in the name of Smith also shows an injector using engine cylinder pressure to develop the injecting pressure. The Smith apparatus uses a non-return valve as the injection valve. A solenoid operated non-return valve is provided in the outlet from the pumping chamber and an adjustable flow restrictor is provided in the outlet line downstream of the non-return valve to enable adjustment of the possible rate of flow when the solenoid non-return valve is opened. In a similar manner to the French US patent, the Smith injector has very limited ability to enable control of the injector operation including timing, injection pressure, volume of fluid injected, and degree of positiveness in action.

U.S. Pat. No. 4,427,151 in the name of Trenne shows a similar injector to the Smith injector except that there is provision for adjusting the clearance between the outlet valve member controlled by the solenoid and its associated seat so that that adjustment enables some control of the flow rate for fuel flowing out of the control chamber. As with the French and Smith specifications, the Trenne injector has limited degrees of control and limited positiveness in operation, particularly the non-return injector valve.