Why is the pressure in the Vito's fuel low-pressure circuit too low?
2 Answers
Low pressure in the Vito's fuel low-pressure circuit can be caused by damaged injectors, incorrect pressure sensor signals, and other reasons. Specific causes of low pressure: Internal blockage in the high-pressure fuel pump or abnormal operation of the pressure regulator. The cold start solenoid valve is stuck in the normally open position. Damaged injectors, leading to excessive fuel return or large amounts of fuel leaking into the cylinders. Bends, collapses, or blockages in the low-pressure fuel line causing poor fuel supply. Incorrect pressure sensor signals. Damaged electric fuel pump. Meaning of the low-pressure circuit: The so-called low-pressure fuel circuit refers to the fuel line from the fuel tank to the high-pressure fuel pump; in other words, the fuel line through which the fuel passes before being pressurized by the pump is called the low-pressure fuel circuit. The low-pressure circuit refers to the fuel line returning from the fuel metering valve.
While driving my Vito for delivery, I noticed the low fuel pressure was too low, making the vehicle hard to start and accelerating unsteadily. Possible causes include an aging and worn fuel pump leading to insufficient fuel supply, especially after prolonged operation when the pump's efficiency declines; a clogged fuel filter with accumulated impurities obstructing flow, common in vehicles with untimely maintenance; a faulty pressure regulator causing unstable control and affecting overall pressure; leaks in the fuel system such as loose or broken pipe connections leading to pressure drops; or damaged sensors like the fuel pressure sensor giving incorrect readings. It is advised to stop the vehicle immediately and not risk driving further. Check the fuel filter first—if dirty, replacing it might be a simple fix; otherwise, seek professional inspection. Regularly replace the fuel filter every 50,000 km and inspect the pump every 100,000 km for prevention. For safety, do not ignore warning lights to avoid engine damage.
