Test 5, 6, & 7 - Fuel System Pressure Leakdown (Decay)

Description:

CAUTION:
^ DO NO NOT ALLOW SMOKING OR THE USE OF OPEN FLAMES IN THE AREA WHERE WORK ON THE FUEL SYSTEM IS TAKING PLACE. ANYTIME WORK IS BEING DONE ON THE FUEL SYSTEM, DISCONNECT THE NEGATIVE BATTERY CABLE, EXCEPT FOR THOSE TESTS WHERE BATTERY VOLTAGE IS REQUIRED.
^ WHENEVER FUEL LINE FITTINGS ARE LOOSENED OR REMOVED, WRAP A SHOP CLOTH AROUND THE FITTING AND HAVE AN APPROVED CONTAINER AVAILABLE TO COLLECT ANY FUEL.
^ FUEL SUPPLY LINES WILL REMAIN PRESSURIZED FOR LONG PERIODS OF TIME AFTER THE ENGINE IS SHUTDOWN. THIS PRESSURE MUST BE RELIEVED BEFORE SERVICING THE FUEL SYSTEM.

IMPORTANT:
Battery must be at a minimum of 12 volts when performing any fuel system tests.

TEST 5 - FUEL SYSTEM LEAKDOWN TEST
The fuel system leakdown test will determine if the fuel system is able to hold fuel pressure when the fuel pump is not operating. The system must hold pressure to assure that the fuel supply circuit (fuel lines, filter/regulator, and fuel rail) is full of fuel. When the fuel supply is completely charged, fuel will be available at the injectors as soon as the ignition is turned on.

1. Remove air induction tube.
2. Perform Fuel Pressure Release procedure.
3. Connect fuel gauge pressure 1 adapter (309725) and pressure gauge to fuel pressure test port.
4. Energize fuel pump (refer to "Energizing the Fuel Pump") for a minimum of 10 seconds.
a. Record fuel pressure.
b. Repeat this procedure a minimum of two times.
5. Shut fuel pump OFF and wait 5 minutes.
6. Record fuel pressure and subtract from pressure recorded in Step 4.
7. Compare pressure loss (decay) to published specification.
^ Maximum Pressure Decay after 5 Minutes = 8 psi (55 kPa).
8. Refer to "Fuel System Diagnostic Chart" and use test result to make appropriate decision.

Description:

6 - FUEL SUPPLY LEAKDOWN TEST
This test will determine if the fuel supply system, up to the fuel rail and injectors, will maintain pressure after the fuel pump is turned off.

NOTICE: This test can be performed using the fuel pressure line quick-connect adapter (309728) or the fuel flow/pressure test adapter (SA9127E-7).

1. Remove air induction tube.
2. Perform Fuel Pressure Release procedure
3. Remove fuel feed line retainer clip attachment screw (10mm hex)
4. Disconnect fuel feed line at fuel rail.

a. Connect fuel feed line directly to pressure gauge using (309728) quick-connect adapter (3/8" x 1/4").

NOTICE: To properly utilize the fuel flow/pressure test adapter it must always be connected with the fuel feed line on the "INLET" side of the adapter and the fuel return or drain line connected to the side with the flow control (ON/OFF) valve. If not connected properly, a "zero" pressure reading will always be read. Use the appropriately sized connector fittings to hookup the adapter to the feed and return lines.

Description:

b. If using the fuel flow/pressure test adapter. connect "INLET" to fuel feed line and assure that flow valve is OFF
5. Connect pressure gauge to test adapter.
6. Energize fuel pump (refer to "Energizing the Fuel Pump") for a minimum of 10 seconds.
a. Record fuel pressure.
b. Repeat this procedure a minimum of two times.
7. Shut fuel pump OFF and wait 5 minutes.
8. Record fuel pressure and subtract from pressure recorded in step 6.
9. Compare pressure loss (decay) to published specification.
^ Maximum Pressure Decay after 5 Minutes = 8 psi (55 kPa).
10. Refer to "Fuel System Diagnostic Chart" and use test result to make appropriate decision

7 - FUEL PUMP LEAKDOWN TEST
This test will determine if the fuel pump will maintain pressure after the pump is turned OFF. For this test the vehicle will be raised on the hoist and a means of controlling the fuel pump from under the vehicle is required. The SCAN tool readily provides this function (refer to 'Energizing the Fuel Pump" in this manual).

1. Connect SCAN tool to vehicle and turn Ignition to On.

2. Perform Fuel Pressure Release procedure
3. Raise vehicle to comfortable working position.
4. Disconnect fuel feed (5/16 in.) and fuel return (3/8 in.) lines at fuel filter/pressure regulator.

Description:

NOTICE: To properly utilize the fuel flow/pressure test adapter it must always be connected with the fuel feed line on the "INLET" side of the adapter and the fuel return or drain line connected to the side with the flow control (ON/OFF) valve. If not connected properly, a "zero" pressure reading will always be read. Use the appropriately sized connector fittings to hookup the adapter to the feed and return lines.

5. Connect fuel flow/pressure test adapter (SA9127E-7) to 1 feed and 2 return lines and make sure connections are firmly latched.
6. Connect fuel pressure gauge to test adapter.
7. Turn On/Off flow valve on test adapter to On.
8. Energize fuel pump.
a. Cycle On/Off flow valve at least two times over a 10 second interval.
b. Turn On/Off flow valve to Off.
c. Record fuel pressure.
9. Shut fuel pump Off and wait 5 minutes.
10. Record fuel pressure and subtract from pressure recorded in Step 8.
11. Compare pressure loss (decay) to published specification.
^ Maximum Pressure Decay after 5 Minutes = 8 psi (55 kPa).
12. Return to "Fuel System Diagnostic Chart" and use test result to make appropriate decision.