Tools Required

If the vehicle is not operating, will not start or run, then determination must be made if the fuel pump is working and fuel under pressure is delivered to the fuel rail.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.

1. Verify that there is fuel in the fuel tank before starting any fuel system diagnosis.
2. Remove the cap on the fuel pressure test port on the fuel rail and slightly depress the top of the Schrader valve and note whether fuel is present.

•	If fuel, under pressure, is present, proceed to test 2 -- Fuel System Pressure Test.

•	If no fuel is present, verify that there is fuel in the tank. Check the fuel gage.

3. Evaluate the fuel pump electrical circuit. Refer to Chart 4 of Engine Cranks But Won't Start.

This test will determine whether there is adequate fuel pressure delivered to the fuel injectors to start and run the engine under low load conditions.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.
2. Connect the fuel gage pressure adapter 309725 and the pressure gage to the fuel pressure test port.

Important: Battery must be at a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding, if below 12 volts. The minimum pressure is 345 kPa 50 psi). The maximum pressure is 414 kPa (60 psi).

3. Using a scan tool, energize the fuel pump for a minimum of 10 seconds.

3.1.	Record the fuel pressure.

3.2.	Repeat this procedure a minimum of 2 times.

4. While the fuel pump is energized, remove the fuel pressure regulator vacuum line and inspect both ends for liquid fuel.

•	If liquid fuel is present, replace the fuel pressure regulator before proceeding. Refer to Fuel Pressure Regulator Removal.

•	If no liquid is present, proceed to Step 5.

5. Compare the pressure recorded to the published specification.
6. Return to the Fuel System Diagnostic Chart and use the test result to make an appropriate decision.

These tests will determine whether the fuel system can supply adequate volume of fuel at the desired pressure to operate the engine under full load conditions. The test is done at 4 points in the system to isolate and identify the problem component:

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be at a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




2. Disconnect the fuel feed and return lines at the fuel rail transfer line.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

3. Connect the inlet side of the SA9127E-7 into the fuel feed line quick connect and make sure the fitting is firmly latched.
4. Connect the fuel pressure gage to the test adapter.
5. Connect the fuel flow/pressure test adapter outlet end to a fuel return hose and place the other end of the hose into an approved container for fuel or fill neck inlet.
6. Turn the ON/OFF valve on the SA9127E-7 to ON.

Important: The unregulated fuel pressure minimum is 380 kPa (55 psi).

7. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

7.1.	Record the fuel pressure.

7.2.	Repeat this procedure a minimum of 2 times.

8. Compare the pressure recorded to the published specification.
9. Refer to Fuel System Diagnostic Chart and use the test result to make appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be at a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding, if below 12 volts.

1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




2. Disconnect the fuel feed line at the fuel filter inlet.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

3. Connect the inlet side of the SA9127E-7 into the fuel feed line quick connect and make sure the fitting is firmly latched.
4. Connect the fuel pressure gage to the test adapter.
5. Connect the fuel flow/pressure test adapter outlet end to the fuel return line or to a fuel return hose and place the other end of the hose into an approved container for fuel or fill neck inlet.
6. Turn the ON/OFF valve on the fuel flow/pressure test adapter to ON.

Important: The unregulated fuel pressure minimum is 380 kPa (55 psi).

7. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

7.1.	Record the fuel pressure.

7.2.	Repeat this procedure a minimum of 2 times.

8. Compare the pressure recorded to the published specification.
9. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




2. Disconnect the fuel feed line at the fuel filter outlet.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

3. Connect the inlet side of the SA9127E-7 onto the fuel filter quick connect and make sure the fitting is firmly latched.
4. Connect the fuel pressure gage to the test adapter.
5. Connect the SA9127E-7 outlet end to the fuel return line or to a fuel return hose and place the other end of the hose into an approved container for fuel or fill neck inlet.
6. Turn the ON/OFF valve on the SA9127E-7 to ON.

Important: The unregulated fuel pressure minimum is 380 kPa (55 psi).

7. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

7.1.	Record the fuel pressure.

7.2.	Repeat the procedure a minimum of 2 times.

8. Compare the pressure recorded to published specification.
9. Refer to Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




2. Disconnect the fuel feed line between the chassis bundle and the front fuel feed line, at the passenger side front wheel well.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

3. Connect the inlet side of the SA9127E-7 onto the fuel filter quick connect and make sure the fitting is firmly latched.
4. Connect the fuel pressure gage to the test adapter.
5. Connect the fuel flow/pressure test adapter outlet end to the fuel return line or to a fuel return hose and place the other end of the hose into an approved container for fuel or fill neck inlet.
6. Turn the ON/OFF valve on the fuel flow/pressure test adapter to ON.

Important: The unregulated fuel pressure minimum is 380 kPa (55 psi).

7. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

7.1.	Record the fuel pressure.

7.2.	Repeat the procedure a minimum of 2 times.

8. Compare the pressure recorded to the published specification.
9. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

These tests will determine whether the fuel pressure regulator, fuel pump (housing), or fuel return lines are operating to engineering specifications. The fuel system pressure in these tests are always measured at the fuel system pressure port, on the fuel rail, regardless of which test is being done (4A, 4B, or 4C).

For some of these tests the vehicle will be raised on a hoist and a means of controlling the fuel pump from under the vehicle will be required. The scan tool readily provides this function. Refer to Energizing The Fuel Pump.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Connect the scan tool to the vehicle and turn the ignition to ON.
2. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




3. Disconnect the fuel return line at the fuel rail.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

4. Connect the SA9127E-7 inlet to the fuel rail return line.

Important: Do not connect the SA9127E-7 outlet to the return line.

5. Connect the outlet side of the SA9127E-7 to a fuel return hose and place the other end of the return hose into an approved container for fuel or fill neck inlet.
6. Cap the SA9127E-7 pressure test port with the J 43936 .

Important: The maximum fuel pressure under flow on the fuel rail is 517 kPa (75 psi).

7. Connect the fuel pressure gage to the fuel pressure test port, on the fuel rail, using the special tool 309725. Ensure the valve is closed.
8. Turn the ON/OFF valve on the SA9127E-7 to ON.
9. Energize the fuel pump for a minimum of 10 seconds.

9.1.	Record the fuel pressure.

9.2.	Repeat this procedure a minimum of 2 times.

10. Compare the pressure recorded to the published specification.
11. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Connect the scan tool to the vehicle and turn the ignition to ON.
2. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




3. Raise the vehicle to a comfortable working position.
4. Disconnect the fuel return line between the front fuel return line and the chassis fuel return line at the passenger side front wheel well.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

5. Connect the SA9127E-7 inlet to the fuel rail return line.
6. Connect the outlet side of the test adaptor to a fuel return hose.
7. Place the other end of the return hose into an approved container for fuel or fill neck inlet.

Important: The maximum fuel pressure under flow on the fuel rail is 517 kPa (75 psi).

8. Cap the SA9127E-7 pressure test port with the J 43936 .
9. Connect the fuel pressure gage to the fuel pressure test port, on the fuel rail, using the special tool 309725. Ensure the valve is closed.
10. Turn the ON/OFF valve on the SA9127E-7 to ON.
11. Energize the fuel pump for a minimum of 10 seconds.

11.1.

Record the fuel pressure.

11.2.

Repeat this procedure a minimum of 2 times.

12. Compare the pressure recorded to the published specification.
13. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Connect the scan tool to the vehicle and turn the ignition to ON.
2. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




3. Raise the vehicle to a comfortable working position.
4. Disconnect the fuel return line between the chassis bundle and the fuel tank return line.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

5. Connect the SA9127E-7 inlet to the chassis bundle return line.
6. Connect the outlet side of the test adaptor to a fuel return hose.
7. Place the other end of the return hose into an approved container for fuel or fill neck inlet.
8. Cap the SA9127E-7 pressure test port with the J 43936 .

Important: The maximum fuel pressure under flow on the fuel rail is 517 kPa (75 psi).

9. Connect the fuel pressure gage to the fuel pressure test port, on the fuel rail, using the special tool 309725. Ensure the valve is closed.
10. Turn the ON/OFF valve on test adapter to ON.
11. Energize the fuel pump for a minimum of 10 seconds.

11.1.

Record the fuel pressure.

11.2.

Repeat this procedure a minimum of 2 times.

12. Compare the pressure recorded to the published specification.
13. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

The fuel system leakdown tests 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 ensure that the fuel supply circuit (fuel lines, filter, pressure regulator, lines, 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.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.
2. Connect the fuel gage pressure adapter 309725 and the pressure gage to the fuel pressure test port.

Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

3. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

3.1.	Record the fuel pressure.

3.2.	Shut the fuel pump OFF.

3.3.	Wait 5 minutes.

Important: During the fuel system leakdown test, the maximum pressure decay after 5 minutes is 55 kPa (8 psi)

4. Record the fuel pressure and subtract from the pressure recorded in Step 3. Repeat this procedure a minimum of 2 times.
5. Compare the pressure loss (decay) to the published specification.
6. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.
2. Disconnect the fuel feed and the return line at the fuel rail.



3. Connect the SA9127E-7 inlet to the fuel feed line and the SA9127E-7 outlet to the fuel return line.

3.1.	Close the valve on the outlet side of the tool.

3.2.	Connect the pressure gage to the SA9127E-7 .

Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

4. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

4.1.	Record the fuel pressure.

4.2.	Shut the fuel pump Off.

4.3.	Wait five minutes.

Important: During the fuel system leakdown test, the maximum pressure decay after 5 minutes is 55 kPa (8 psi).

5. Record the fuel pressure and subtract from the pressure recorded in Step 3. Repeat this procedure a minimum of 2 times.
6. Compare the pressure loss (decay) to the published specification.
7. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.



2. Disconnect the fuel feed and the return line at the fuel rail.
3. Connect the SA9127E-7 inlet to the fuel rail return side and the outlet to the front fuel return line.

3.1.	Close the valve on the outlet side of the tool.

3.2.	Connect the pressure gage to the SA9127E-7 .

Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

4. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

4.1.	Record the fuel pressure.

4.2.	Shut the fuel pump OFF.

4.3.	Wait 5 minutes.

Important: During the fuel system leakdown test, the maximum pressure decay after 5 minutes is 55 kPa (8 psi).

5. Record the fuel pressure and subtract from the pressure recorded in Step 3. Repeat this procedure a minimum of 2 times.
6. Compare the pressure loss (decay) to the published specification.
7. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

These tests will determine whether the fuel system, fuel pump, fuel filter, and fuel pressure regulator can supply the fuel at the adequate pressure.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




2. Disconnect the fuel feed and the return lines at the fuel rail.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

3. Connect the inlet side of the SA9127E-7 into the line.
4. Connect the outlet side of the SA9127E-7 into the fuel return line.
5. Connect the fuel pressure gage to the test adapter.

Unregulated Fuel Pressure Under Flow on Fuel Flow/Pressure Adapter - L61 = Maximum -- 380 kPa (55 psi)

Important: The unregulated fuel pressure minimum is 380 kPa (55 psi).

6. Turn the ON/OFF valve on the SA9127E-7 to ON.
7. Energize the fuel pump for a minimum of 10 seconds.

7.1.	Record the fuel pressure.

7.2.	Repeat this procedure a minimum of 2 times.

8. Compare the pressure recorded to the published specification.
9. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.





Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

1. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.




2. Disconnect the fuel feed at the fuel filter inlet and fuel return line at the front of the fuel tank.

Important: To properly utilize the SA9127E-7 , 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 hook up the adapter to the feed and return lines.

3. Connect the inlet side of the SA9127E-7 into the fuel feed line line.
4. Connect the outlet side of the SA9127E-7 to the tank fuel return line.
5. Connect the fuel pressure gage to the test adapter.
6. Turn the ON/OFF valve on the SA9127E-7 to ON.

Important: The unregulated fuel pressure minimum is 380 kPa (55 psi).

7. Energize the fuel pump for a minimum of 10 seconds. Refer to Energizing the Fuel Pump.

7.1.	Record the fuel pressure.

7.2.	Repeat this procedure a minimum of 2 times.

8. Compare the pressure recorded to the published specification.
9. Refer to the Fuel System Diagnostic Chart and use the test result to make the appropriate decision.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.




1. Remove the air cleaner inlet tube.
2. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.

3. Connect the pressure gage adapter 309725 to the fuel pressure test port.
4. Remove the fuel line attachment screw and fuel lines from the clamp.




Caution: Lay shop towels on the intake manifold and cam cover to collect any fuel.

Caution: Make sure the injectors are positioned to prevent fuel from being sprayed onto the engine. Make sure that the injector retaining clips are properly installed.

5. Remove the fuel rail assembly. Refer to Fuel Rail Replacement.

5.1.	Pull the fuel rail back far enough so that the nozzles of the injectors are visible but still in the ports.

5.2.	Attach the fuel rail to the intake manifold with a wire.

6. Connect the fuel pressure gage bar to the pressure adapter.
7. Wipe the tips of the fuel injectors free of any fuel or debris.

7.1.	Place a clean, white towel directly under the fuel injectors.

7.2.	Ensure the towel lightly contacts each fuel injector tip.

8. Connect the scan tool and turn the ignition ON.

Important: The battery must be a minimum of 12 volts when performing any fuel system test. Charge the battery before proceeding if below 12 volts.

9. Energize the fuel pump. Refer to Energizing Fuel Pump.
10. Observe the fuel injector tops for leakage of fuel. If one or more of the white towels becomes wet with fuel after 5 minutes, replace the faulty fuel injector. Refer to Fuel Injector Assembly.

Important: The pressure gage reading should be approximately 345-414 kPa (50-60 psi).

11. Test the assembly a minimum of 2 times.
12. Install the bleed hose from the pressure test adapter 309725 into an approved container.
13. Open the valve to bleed the system pressure.
14. Remove the fuel pressure adapter from the fuel pressure test port.
15. Install the fuel pressure test port cap.
16. Lubricate the injector O-rings with clean engine oil and install the fuel rail assembly. Refer to Fuel Rail Replacement.
17. Start the engine and check for leaks.

Caution: Refer to Gasoline/Gasoline Vapors Caution in the Preface section.

Important: If the engine is at operating temperature, allow a 10 minute cool down period.

1. Before the Fuel Injector Balance Test is started, the electrical connector should be tested using a noid light.

1.1.	Disconnect the harness connectors at the fuel injectors.

1.2.	Connect a noid light to the female connector.

1.3.	Crank the engine.





1.4.	If the noid light does not blink, the electrical problem must be corrected before continuing.

1.5.	Remove the noid light and install the connectors on the injectors.

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.

2. Connect the scan tool and turn the ignition ON.
3. Relieve the fuel system pressure. Refer to Fuel System Pressure Relief.
4. Energize the fuel pump. Refer to Energizing Fuel Pump.
5. Ensure that the fuel pressure is between 345-414 kPa (50-60 psi) (1st Reading).
6. Record the pressure at the instant the gage needle stops moving. (2nd Reading)
7. Repeat steps 1-3 for the remaining 3 injectors.

Notice: The engine must be started after four cylinders have been tested to prevent flooding or internal damage.

8. Add all the 2nd Readings together and divide by 4. This is the 2nd Reading average.
9. Subtract the Average of 2nd Reading from each 2nd Reading to obtain the Difference.
10. An injector is faulty if the Difference is greater than 8.5-11.5 kPa.
11. Check that all fuel injector connectors are connected. Pull back to ensure a positive engagement.
12. Remove the fuel gage bar adapter from the fuel pressure test port and recap it.
13. Install the air cleaner inlet tube.
14. Start the engine and check for leaks.