Fueling Connector
The flange assembly is designed for 3000 psi (20,685 kPa) service pressure and is the refueling connection to
fill vehicle. The assembly is mounted behind fuel filler door and attached to fuel filler housing, similar to a
gasoline vehicle. This assembly consists of an NGVP1 type receptacle with a 150-micron filter (which can be
serviced), a spring loaded check valve to allow filling of vehicle and a instructionly opened bypass to provide safe
venting of fuel system. The vehicle is refueled by attaching fuel station fill nozzle to receptacle and locking into
place.
Fuel Lines & Fittings
A fuel line assembly consists of flexible hose and/or stainless steel seamless tubing, end fittings and tube nuts.
The hose is a conductive polytetrafluoroethylene (PTFE) liner reinforced with a stainless steel wire braided
covering. The fittings are inserted into hose ends and crimped into place. The stainless steel tubing contains end
fittings which are brazed to the tube. There are high pressure fuel lines that are identified by either 1/4-inch or
3/8-inch outer diameter, and a low pressure fuel line identified by a 1/2-inch outer diameter. The low pressure
fuel line has a quick-connect at one end for connection to fuel rail. The other fittings used on natural gas vehicle
to connect fuel components are SAE "O" ring face seal tube fittings. There are 2 end types: an "O" ring face
seal end and a straight thread end. On tee and elbow fittings, a washer and a positionable nut are provided to aid
in orientation of the fitting.
Fuel Rail
The fuel rail distributes low pressure fuel from chassis supply line to each fuel injector. Fuel pressure at top of
each fuel injector is maintained within 1 percent of other fuel injectors at all times, done by nearly symmetric
flow paths. The fuel rail is also designed to have minimal flow restriction by increasing cross-sectional flow
area and reducing flow path length. The fuel rail contains several other components that perform crucial
functions. See Fig. 43 . These include:
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Injection Pressure Sensor
Measures the pressure of fuel near fuel injectors. This signal is used by PCM to adjust fuel injector pulse
width and meter fuel to each cylinder.
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Engine Fuel Temperature Sensor
Measures pressure of fuel near fuel injectors. This signal is used by PCM to adjust fuel injector pulse
width and meter fuel to each cylinder.
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Low Pressure Solenoid Shutoff Valve
Isolates fuel rail from upstream fuel system when engine is OFF. This minimizes the amount of fuel
available to flow through fuel injectors when engine is off or leak from a damaged fuel rail during and
after a crash. The valve is controlled by PCM fuel shutoff valve circuit and contains an inertia switch. The
valve is only on for one second after a key-on or whenever CKP signals are being received by PCM.
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Schrader/Service Valve
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline