Fuel pump cut-off circuit

Claim 1

In an electronic fuel injection control system for an internal combustion engine having an electromagnetic fuel pump, a fuel pump relay, fuel metering means, a signal source of ignition pulses, and a supply voltage, a fuel pump cut-off circuit comprising: a first comparator means; a second comparator means; a first wave shaping/timing means coupling said signal source of ignition pulses to the non-inverting input of said first comparator means; said first wave shaping/timing means for reshaping said ignition pulses in a predetermined way to create a newly shaped pulse train which is one half the frequency of the said signal source of ignition pulses; a reference voltage means which presents a preselected reference voltage to the inverting input of said first comparator means and to the non-inverting input of said second comparator means; a second wave shaping/timing means for reshaping the output of said first comparator means in a predetermined way such that said signal source of ignition pulses below a preselected reference frequency will not cause a change in the output state of said second comparator means; said second comparator means which accepts at its inverting input the output of said first comparator means as reshaped by said second timing means and accepts at its non-inverting input said preselected reference voltage from said reference voltage means; and fuel pump driver means connected to the output of said second comparator means and responding thereto for controlling the energization and deenergization of said fuel pump relay.