Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel-quantity control valve and high-pressure pump: Notes
The fuel-quantity control valve is mounted on the high-pressure pump (CP4.2). The fuel-quantity control valve is controlled using a pulse-width-modulated signal. The DDE controls the fuel-quantity control valve at various pulse-duty factors while the fuel-quantity control system is active. The system adjust rail pressure to the specified level as calculated by the DDE.
The fuel-quantity control valve regulates the fuel flow from the low-pressure side to the high-pressure side of the high-pressure pump. This is how the desired fuel-rail pressure is achieved. Progressive reductions in the amount of fuel that the fuel-quantity control valve allows to flow to the high-pressure side produce corresponding reductions in the level to which the high-pressure pump charges the cylinders. The consequence is that less rail pressure is built up.
The high-pressure pump generates pressure to maintain a constant level in the rail. Two valves are employed to maintain the pressure within the fuel rail at the required level:
- Fuel quantity control valve
- Rail-pressure control valve (see corresponding description of operation)
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.