Ford F150 Pickup. Instruction — part 1635

Fig. 45: Identifying Fuel Tank Shutoff Valve
Courtesy of FORD MOTOR CO.

Inertia Fuel Shutoff Switch

See INERTIA FUEL SHUTOFF SWITCH (ALL FUEL SYSTEMS) under FUEL SYSTEMS
(GASOLINE).

NG Fuel Pressure Regulator

The fuel pressure regulator used in the Natural Gas fuel system is a single-stage pressure reducing regulator
which expands natural gas from storage pressures of 200-3000 psi (1379-20,685 kPa) to engine fuel injector
pressures of 105-125 psi (724-862 kPa).

The regulator contains a pressure relief device, a 275 psi (1896 kPa) check valve, which protects the low
pressure fuel system. The low pressure fuel system no longer must fulfill the design requirements of the high
pressure fuel system, therefore reducing cost, weight and complexity.

When gas expands, the fuel temperature drops significantly causing extreme cold temperatures (-160°F or -177°
C) that may damage synthetic fuel system components as well as cause water vapor within the fuel to condense,
freeze and plug the lines, valve and injectors. To prevent this, engine coolant is routed through the fuel pressure
regulator to warm the fuel before it expands.

The regulator has an internal thermostat to control the flow of engine coolant. This prevents overheating and
subsequent thinning of the fuel which may cause lean combustion. Outlet coolant flow is restricted by the
thermostat when it rises above approximately 100°F (82°C).

FUEL CONTROL

Natural Gas Vehicle Module

See NATURAL GAS VEHICLE MODULE under COMPUTERIZED ENGINE CONTROLS.

NG Fuel Injectors

The fuel injector is a solenoid-operated valve that meters fuel flow to the engine. The fuel injector is opened and
closed every other crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector
is held open.

The fuel injector is normally closed and is operated by 12 volt VPWR from the power relay. The ground signal
is controlled by the PCM.

The fuel injectors are used to meter natural gas to each combustion cylinder. Although the natural gas fuel

WARNING:

DO NOT reset IFS switch until complete fuel system has been inspected
for leaks.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

injectors appear very similar to some gasoline fuel injectors, they are unique. Flow capacity of these fuel
injectors is 6 to 12 times as large as various gasoline fuel injectors. Electrical resistance is much lower than
typical gasoline fuel injectors (4.6 ohms as opposed to 14.5 ohms). To accommodate this lower resistance, a
fuel injector driver module is used to convert the PCM fuel injector driver signal to the signal required by the
fuel injector.

IDLE SPEED

IDLE CONTROL SYSTEM

Idle Air Control Valve Assembly

Idle Air Control (IAC) valve assembly is used to control idle speed and provide a dashpot function. IAC valve
assembly meters inlet air around the throttle plate through a by-pass within the IAC valve assembly and throttle
body. See Fig. 46 -Fig. 48 .

The Powertrain Control Module (PCM) determines desired idle speed or air by-pass and signals the IAC valve
assembly through specified duty cycle. The IAC solenoid is built into IAC valve assembly. IAC solenoid
responds by positioning the IAC valve to control amount of air by-passed. PCM monitors engine speed and
adjusts IAC duty cycle to achieve desired RPM. IAC valve assembly is not adjustable and cannot be cleaned.

On applications with air assisted injectors, IAC valve supplies a small jet of air into path of fuel injectors,
creating an increase in fuel atomization at low speed and light load conditions. See Fig. 47 .

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

Fig. 46: Cross-Sectional View Of Idle Air Control Valve Assembly With Air Vent/Filter (Hitachi)
Courtesy of FORD MOTOR CO.

Fig. 47: Cross-Sectional View Of Idle Air Control Valve Assembly With Air Assist Injectors (Hitachi)
Courtesy of FORD MOTOR CO.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

Fig. 48: Cross-Sectional View Of Idle Air Control Valve Assembly Components (Nippondenso)
Courtesy of FORD MOTOR CO.

IGNITION SYSTEMS

INTEGRATED ELECTRONIC IGNITION SYSTEM

Description

Integrated Electronic Ignition (EI) system consists of a Crankshaft Position (CKP) sensor, coil pack(s), wiring
and PCM. Coil On Plug (COP) integrated EI system uses a separate coil for each spark plug and each coil is
mounted directly onto spark plug. COP integrated EI system eliminates need for spark plug wires but does
require input from Camshaft Position (CMP) sensor. The following list of components and their specific
operation corresponds to numbers in illustration. See Fig. 49 .

1. The CKP sensor is used to indicate crankshaft position and speed by sensing a missing tooth on a pulse

wheel mounted to crankshaft. The CMP sensor is used by COP Integrated EI System to identify top dead
center of compression of cylinder No. 1 to synchronize firing of individual coils. For additional CKP or
CMP sensor information, see CAMSHAFT POSITION SENSOR or CRANKSHAFT POSITION
SENSOR under INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS.

NOTE:

Ignition timing is controlled by the Powertrain Control Module (PCM) and is not
adjustable. DO NOT attempt to check base timing as false readings will result.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline