Fuel supply systems for diesel engines

Claim 1

A fuel supply system for a diesel engine comprising in combination a pump for supplying fuel to the engine, an electrically operated actuator for controlling the output of the pump, a pair of D.C. supply lines, a voltage regulator for restricting the potential across said supply lines to a first predetermined value, a series circuit connected across said supply lines and including a resistor, a relay winding and a first transistor, first means for turning said transistor off when the current flowing in the actuator exceeds a predetermined value, including a Zener diode which is arranged to break down when the current flow through the actuator exceeds said predetermined value, a second transistor which is turned on by the current flow in the Zener diode, said second transistor removing the base drive to said first transistor when rendered conductive, second means operable upon de-energization of the relay winding when the transistor is turned off for preventing operation of the actuator, switch means for short-circuiting said resistor if the potential between the supply lines falls below a second predetermined value and third means for maintaining the current flow in said Zener diode when the actuator is turned off.