Gasoline Engines
1. Remove fuel cap to release fuel tank pressure. Remove relief valve service port cap. Relief valve service
port is located on fuel supply manifold. Using Fuel Pressure Gauge (T80L-9974-B), release fuel pressure
from Schrader valve.
2. If fuel pressure gauge is not available, disconnect electrical connector to Inertia Fuel Shutoff (IFS)
switch. For IFS switch location, see INERTIA FUEL SHUTOFF SWITCH LOCATIONS table. Crank
engine with IFS disconnected for 15 seconds to reduce system pressure.
FUEL PRESSURE
Bi-Fuel & Natural Gas Vehicle Engines
1) Check Fuel Pressure
Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Install Natural
Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail Schrader valve. Using scan tool, access
FRP PID (if available) from PID/DATA MONITOR & RECORD menu. With ignition switch turned to
ON position, record FRP sensor PID or fuel pressure gauge reading. Start engine and allow to idle. Again
record FRP sensor PID or fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain
for one minute. Record FRP sensor PID or fuel pressure gauge reading. Compare measured fuel pressure
to fuel pressure specification. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure
readings are within specification, turn ignition switch to OFF position and go to next step. If fuel pressure
readings are not within specification, turn ignition switch to OFF position and go to TEST HB, step 1)
under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG, FLEX-FUEL & GASOLINE article
for fuel delivery system diagnosis.
2) Check Fuel System For Pressure Stability
With fuel pressure gauge installed, cycle ignition switch from OFF to ON position 2 times to pressurize
fuel system (DO NOT start engine). Verify no external leaks are present. If fuel pressure does not remain
within 10 psi (69 kPa) of highest fuel pressure reading after 2 minutes, go to TEST HB, step 1) under
components.
NOTE:
For fuel pressure release procedures on Bi-Fuel and Natural Gas Vehicles
(NGV), see appropriate REMOVAL & INSTALLATION article.
WARNING:
Fuel system remains under high pressure even when engine is not
running. To avoid injury, release fuel pressure before disconnecting
any fuel system hose or component. See appropriate FUEL SYSTEM
PRESSURE RELEASE procedure under FUEL SYSTEM VENTING in
appropriate REMOVAL, OVERHAUL & INSTALLATION article.
NOTE:
Not all natural gas vehicles are equipped with Fuel Rail Pressure (FRP)
sensor. On vehicles without FRP sensor, use values supplied by fuel rail
pressure gauge.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Basic Diagnostic Procedures - Trucks - Except Diesel