VehiCROSS 4WD V6-3.5L (1999)
-
The fuel injector(s).
4. Fuel pressure that drops off during acceleration, cruise, or hard cornering may cause a lean condition. A lean condition can cause a loss of power,
surging, or misfire. A lean condition can be diagnosed using a Tech 2. If an extremely lean condition occurs, the oxygen sensor(s) will stop
toggling. The oxygen sensor output voltage(s) will drop below 500 mV. Also, the fuel injector pulse width will increase.
When the engine is at idle, the manifold pressure is low (high vacuum). This low pressure (high vacuum) is applied to the fuel pressure regulator
diaphragm. The low pressure (high vacuum) will offset the pressure being applied to the fuel pressure regulator diaphragm by the spring inside the
fuel pressure regulator. When this happens, the result is lower fuel pressure. The fuel pressure at idle will vary slightly as the barometric pressure
changes, but the fuel pressure at idle should always be less than the fuel pressure noted in step 2 with the engine "OFF."
16. Check the spark plug associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is
leaking. If checking the spark plug associated with a particular fuel injector for fouling or saturation does not determine that a particular fuel
injector is leaking, use the following procedure:
-
Remove the fuel rail, but leave the fuel lines and injectors connected to the fuel rail. Refer to Fuel Rail Assembly in On-Vehicle Service.
-
Lift the fuel rail just enough to leave the fuel injector nozzles in the fuel injector ports.
CAUTION: In order to reduce the risk of fire and personal injury that may result from fuel spraying on the engine, verify that the fuel rail is
positioned over the fuel injector ports and verify that the fuel injector retaining clips are intact.
-
Pressurize the fuel system by connecting a 10 amp fused jumper between B+ and the fuel pump relay connector.
-
Visually and physically inspect the fuel injector nozzles for leaks.
17. A rich condition may result from the fuel pressure being above 376 kpa (55 psi). A rich condition may cause a DTC P0132 or a DTC P0172 to
set. Driveability conditions associated with rich conditions can include hard starting (followed by black smoke) and a strong sulfur smell in the
exhaust.
20. This test determines if the high fuel pressure is due to a restricted fuel return line or if the high fuel pressure is due to a faulty fuel pressure
regulator.
21. A lean condition may result from fuel pressure below 333 kpa (48 psi). A lean condition may cause a DTC P0131 or a DTC P0171 to set.
Driveability conditions associated with lean conditions can include hard starting (when the engine is cold), hesitation, poor driveability, lack of
power, surging , and misfiring.
22. Restricting the fuel return line causes the fuel pressure to rise above the regulated fuel pressure. Command the fuel pump "ON" with the Tech 2.
The fuel pressure should rise above 376 kpa (55 psi) as the fuel return line becomes partially closed.
NOTE: Do not allow the fuel pressure to exceed 414 kpa (60 psi). Fuel pressure in excess of 414 kpa (60 psi) may damage the fuel pressure
regulator.
CAUTION: To reduce the risk of fire and personal injury:
-
It is necessary to relieve fuel system pressure before connecting a fuel pressure gauge. Refer to Fuel Pressure Relief Procedure, below.
-
A small amount of fuel may be released when disconnecting the fuel lines. Cover fuel line fittings with a shop towel before disconnecting, to
catch any fuel that may leak out. Place the towel in an approved container when the procedure is completed.
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Remove the fuel pump relay from the underhood relay center.
3. Start the engine and allow it to stall.
4. Crank the engine for an additional 3 seconds.
Fuel Gauge Installation
1. Remove the shoulder fitting cap.
2. Install fuel gauge J 34730-1 to the fuel teed line located in front of and above the right side valve train
3. Reinstall the fuel pump relay.
