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Test Description

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The numbers below refer to the numbers in the diagnostic table.

  1. 2:  This step verifies that the fuel pump is operating.
  2. 4:  This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
  3. 7:  This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel pump.
  4. 10:  This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.
  5. 11:  This step tests for a leaking fuel injector, or fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.
Fuel System Diagnosis

Step Action Value(s) Yes No
Schematic Reference:  Fuel System Description 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 
IMPORTANT: Inspect the fuel system for damage, or external leaks, before proceeding with this diagnostic.
  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump ON with a scan tool.
Does the fuel pump operate?		 - Go to Step 3  Go to Fuel Pump Electrical Circuit Diagnosis 
3
IMPORTANT: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.
  1. Turn OFF the ignition.
  2. Turn OFF all accessories.
    3. CAUTION: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.
  3. Install the J 34730-1A  Fuel Pressure Gage.
  4. Place the bleed hose of the fuel pressure gage into an approved gasoline container.
  5. Turn ON the ignition, with the engine OFF.
  6. Command the fuel pump ON with a scan tool.
  7. Bleed the air out of the fuel pressure gage.
    8. IMPORTANT:
    • May be necessary to command the fuel pump ON several times, in order to obtain the highest possible fuel pressure.
    • DO NOT start the engine.
  8. Command the fuel pump ON with a scan tool.
  9. Observe the fuel pressure gage, with the fuel pump commanded ON.
Is the fuel pressure within the specified value?		 384-425 kPa (56-62 psi) Go to Step 4  Go to Step 8 
4 
IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.
Observe the fuel pressure gage for 1 minute.Does the fuel pressure drop more than the specified value?		 34 kPa (5 psi) Go to Step 7  Go to Step 5 
5
  1. Relieve the fuel pressure to the first specified value.
  2. Observe the fuel pressure gage for 5 minutes.
Does the fuel drop more than the second specified value?		 69 kPa (10 psi)
14 kPa (2 psi)		 Go to Step 12  Go to Step 6 
6
  1. Operate the vehicle within the conditions of the customers concern.
  2. Observe the fuel related parameters with a scan tool.
Do any of the scan tool parameters indicate a lean condition?		 - Go to Step 9  Go to Symptoms - Engine Controls 
7 
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
  3. Disconnect the fuel feed hose from the fuel rail pipe. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
  4. Install the J 37287  Fuel Line Shut-Off Adaptor between the fuel hoses and the fuel rail pipe.
  5. Open the valve on the fuel pipe shut-off adapter.
  6. Turn ON the ignition, with the engine OFF.
  7. Command the fuel pump ON with a scan tool.
  8. Bleed the air from the fuel pressure gage.
  9. Command the fuel pump ON and then OFF with a scan tool.
  10. Close the fuel feed pipe shut-off valve.
  11. Observe the fuel pressure gage for 1 minute.
Does the fuel pressure remain constant?		 - Go to Step 12  Go to Step 11 
8 Is the fuel pressure more than the specified value? 427 kPa (62 psi) Go to Step 12  Go to Step 9 
9 Inspect the fuel feed pipe for a restriction.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 10 
10  Inspect the harness connectors and ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 12 
11 
  1. Turn OFF the ignition.
  2. Raise the fuel rail, with the fuel lines connected. Refer to Fuel Rail Assembly Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Command the fuel pump ON with a scan tool.
  5. Locate and replace the leaking fuel injector. Refer to Fuel Injector Replacement .
Did you complete the replacement?		 - Go to Step 13  -
12 Replace the fuel pump. Refer to Fuel Sender Assembly Replacement .
Did you complete the replacement?		 - Go to Step 13  -
13 Operate the system in order to verify the repair.
Did you correct the condition?		 - System OK Go to Step 3 
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