Boat Diesel – Bleeding the fuel system

After changing the filter element, the fuel system must be bled to remove any air. First identify, then open the bleed screw on the filter housing (above right). Work the hand priming lever on the lift pump until clear fuel without bubbles flows out. Keep pumping as the bleed screw is tightened down (below right). This is normally the high point in the low pressure system. If it is not then it may be necessary to bleed air from another point, or even the high pressure injector pump.

If the engine does need bleeding from the high pressure injector pump, refer to the manufacturer’s instructions. It is easy to undo the wrong screw on the pump and upset the settings.

Many modern engines incorporate self-bleeding devices which can cope with minor leakages.

If a fuel-assisted cold starting device is fitted, this too may need to be bled. Undo one of the pipe union nuts and follow the same procedure as the bleed screw, and keep pumping as the nut is tightened.

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