Ford F150 Pickup. Instruction — part 1344

NATURAL GAS SYSTEM

Compressed Natural Gas

DO NOT modify system configuration or components, or replace components with parts not specially designed
for use with natural gas. Manufacturer has specially designed the materials, components and system
configuration for natural gas vehicles, and each particular system is precisely calibrated for efficient operation.
Use of different parts or materials can produce an untested configuration that could result in fire or personal
injury, or cause engine damage. It is important the natural gas vehicle be properly maintained by natural gas
trained personnel. If a problem occurs, it is important that properly trained personnel diagnose the cause. If
problem relates to fuel system, proper part replacement is imperative to keep vehicle operating at normal
performance. Natural gas components and gasoline fuel components are not interchangeable. If vehicle is not
serviced in accordance with natural gas-fueled vehicle procedures, damage can occur and warranty may be
invalidated.

DO NOT smoke or carry lighted tobacco or open flame of any type when working on or near any fuel-related
components. Highly flammable mixtures are always present and may be ignited. Failure to follow these
instructions may result in personal injury. Fuel supply lines will remain pressurized after engine shutdown.
When servicing fuel-related components, DO NOT smoke or carry lighted tobacco or any open flame of any
type. Flammable gases may be present and ignite, resulting in possible personal injury. Observe all warnings
when performing the natural gas leak test. See COMPRESSED NATURAL GAS LEAK TEST under FUEL
SYSTEMS.

Inertia Fuel Shutoff Switch Reset Procedure

CAUTION: Natural gas in fuel system is at high pressure at all times. To avoid injury

or fire, release fuel pressure from fuel system before disassembling any
fuel system component. To release fuel system pressure, follow pressure
relief procedure. See FUEL SYSTEM PRESSURE RELEASE in appropriate
REMOVAL & INSTALLATION article. After performing fuel system pressure
relief procedure, a small amount of pressure 3 psi (21 kPa) will remain in
fuel rail, and high pressure still exists in fuel tanks. Prevent combustion
from escaping fuel; no smoking, open flames or any kind of arcing.

NOTE:

Compressed Natural Gas (CNG) may also be referred to as natural gas. Natural
gas is lighter than air.

WARNING:

Use care to prevent combustion from fuel spillage. No smoking, open
flames or any kind of arcing.

WARNING:

If you see or smell gasoline at any time other than during fueling, DO NOT
reset Inertia Fuel Shutoff (IFS) switch.

NOTE:

With IFS in CLOSED position, reset button can be depressed an additional 1/16"
against the spring.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE System & Component Testing - CNG

Turn ignition off. Check for fuel leaks in engine compartment. If no leak is present, reset IFS switch by pushing
reset button on top of switch. Turn ignition on for a few seconds, then off again. Again, check for leaking fuel.

CONNECTOR IDENTIFICATION

CONNECTOR VIEWS

Fig. 5: Identifying Tank Valve In-Line Connector C421 Terminals
Courtesy of FORD MOTOR CO.

NOTE:

For connector views referred to in diagnostic tests, see Fig. 5 and Fig. 6 .

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE System & Component Testing - CNG

Fig. 6: Identifying Fuel Tank Solenoid Valve Connector Terminals
Courtesy of FORD MOTOR CO.

FUEL SYSTEMS

FUEL SYSTEM PRESSURE RELEASE

WARNING:

Before performing any tests or diagnostics on CNG or LPG components
or systems, read all cautions and warnings in CNG/LPG SAFETY
PRECAUTIONS article in GENERAL INFORMATION.

WARNING:

Always release (vent) fuel pressure before disconnecting any fuel
injection-related component downstream of fuel tank shutoff solenoids.
DO NOT vent fuel system indoors.

WARNING:

CNG fuel systems are always pressurized to 100 psi (7 kg/cm

2

)

downstream of fuel pressure regulator. CNG fuel systems are kept up to
3000 psi (211 kg/cm

2

) upstream of fuel pressure regulator. Use care when

servicing CNG fuel systems.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE System & Component Testing - CNG

CNG and LPG fuel pressure must be released prior to any fuel system service. To release CNG fuel pressure,
see FUEL SYSTEM PRESSURE RELEASE in appropriate REMOVAL & INSTALLATION - F150 PICKUP -
NGV article, or FUEL SYSTEM PRESSURE RELEASE in REMOVAL & INSTALLATION article. Failure to
follow these instructions may result in personal injury.

COMPRESSED NATURAL GAS LEAK TEST

Fuel Injection Supply Manifold & Fuel Injectors

NOTE:

After vehicle has hot-soaked for several hours, a very slight natural gas smell
may emanate from within intake manifold and intake air system. This is normal,
as fuel injectors leak down from fuel injection supply manifold to intake
manifold over several hours. Follow all safety precautions. See FUEL SYSTEM
SAFETY PRECAUTIONS and/or CNG/LPG SAFETY PRECAUTIONS article in
GENERAL INFORMATION.

NOTE:

On Crown Victoria, fuel pump relay is referred to as the fuel valve relay.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE System & Component Testing - CNG