Frequency Valve: Description and Operation

Frequency Valve:

CONSTRUCTION
Design and electrical layout is identical to L-Jetronic fuel injector. On fuel inlet side, valve is connected to lower chambers of fuel distributor and is fitted with a connection leading to fuel return line. Control unit feeds frequency valve square pulses of constant frequency (70 Hz.), but of variable pulse width. Pulse width is referred to as pulse-duty factor. Since pulse width is subject to constant changes in control mode, this also indicates system is operative.

Pulse-Duty Factor:

OPERATION
If a pulse is present at frequency valve, valve needle opens to allow flow to return line. Pressure in lower chamber drops until frequency valve is closed again. Since frequency is relatively high, a slightly pulsating medium pressure level is obtained.

Frequency Valve:

As duration of pulses fed by control unit decreases, frequency valve opens only for a short period. Pressure in lower chamber is only slightly reduced. The diaphragm deflects only slightly, differential pressure diminishes and quantity of fuel injected is reduced.

Frequency Valve:

When duration of control pulse is increased, frequency valve is open for a longer period, reducing pressure in lower chamber. The diaphragm deflects to a greater extent, increasing both differential pressure and quantity of fuel injected.