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Fuel system - depressurisation
Fuel and exhaust systems / Fuel system - depressurisation

Warning: The fuel system will remain pressurised for long periods of time after the engine is switched off - this pressure must be released before any part of the system is disturbed. Petrol is extremely flammable, so take extra precautions when you work on any part of the fuel system. DonТt smoke, or allow open flames or bare light bulbs, near the work area.

DonТt work in a garage where a natural gas-type appliance (such as a water heater or clothes dryer) with a pilot light is present. If you spill any fuel on your skin, rinse it off immediately with soap and water. When you perform any kind of work on the fuel system, wear safety glasses, and have a Class B type fire extinguisher on hand.

1 The fuel system referred to in this Chapter is defined as the fuel tank and tank-mounted fuel pump/fuel gauge sender unit, the fuel filter, the fuel injectors and the pressure regulator in the injector rail, and the metal pipes and flexible hoses of the fuel lines between these components. All these contain fuel, which will be under pressure while the engine is running and/or while the ignition is switched on.

2 The pressure will remain for some time after the ignition has been switched off, and must be relieved before any of these components is disturbed for servicing work.

3 The simplest method is simply to disconnect the fuel pumpТs electrical supply while the engine is running - either by removing the fuel pump fuse (number 14), or by lifting the red button on the fuel cut-off switch (see Section 13) - and to allow the engine to idle until it dies through lack of fuel pressure. Turn the engine over once or twice on the starter to ensure that all pressure is released, then switch off the ignition; do not forget to refit the fuse (or depress the red button, as appropriate) when work is complete.

4 The Ford method of depressurisation is to use service tool 29-033 fitted to the fuel rail pressure test/release fitting - a Schrader-type valve with a blue plastic cap, located on the union of the fuel feed line and the fuel rail - to release the pressure, using a suitable container and wads of rag to catch the spilt fuel. Do not simply depress the valve core to release fuel pressure - droplets of fuel will spray out, with a consequent risk of fire, and of personal injury through fuel getting into your eyes.

Warning: Either procedure will merely relieve the increased pressure necessary for the engine to run. Remember that fuel will still be present in the system components, and take precautions accordingly before disconnecting any of them.

5 Note that, once the fuel system has been depressurised and drained (even partially), it will take significantly longer to restart the engine - perhaps several seconds of cranking - before the system is refilled and pressure restored.

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