The fuel metering valve comprises a fuel-cooled solenoid valve. The valve opening is varied by its solenoid coil being pulse width modulated at a frequency of 1 KHz.
When the fuel metering valve is not activated, its internal spring maintains a fuel pressure of about 100 Bar. When the valve is activated, the force of the electromagnet aids the spring, reducing the opening of the valve and so increasing fuel pressure. The valve also acts as a mechanical pressure damper, smoothing the high frequency pressure pulses emanating from the radial piston pump when less than three pistons are activated.