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Inspection Procedure 27

INSPECTION PROCEDURE 27
Fuel Pump System
















WIRING DIAGRAM and CONNECTOR VIEW

CIRCUIT OPERATION
- A battery positive voltage is applied on the fuel pump relay (terminal 3, 4) from the ignition switch-IG.
- During cranking and while the engine is running, the ECM turns the power transistor in the ECM "ON" to ground the fuel pump relay coil. With this, the fuel pump relay turns "ON," and the battery positive voltage is supplied to the fuel pump from the fuel pump relay (terminal 1).

TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the fuel pump relay.
- Malfunction of the fuel pump.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the ECM.

DIAGNOSIS

Required Special Tool:
MB991 502: Scan Tool




STEP 1. Using scan tool MB991502, actuator test item 07: Fuel Pump.

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.

- An operating sound of the fuel pump should be heard. If no sound is heard, go to Step 2.
If a sound is heard, it can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.




STEP 2. Check the fuel pump operation.
(1) Apply battery voltage to the fuel pump check connector A-38.
- An operating sound of the fuel pump should be heard.
If no sound is heard, go to Step 3.
If a sound is heard, go to Step 5.




STEP 3. Check the ground line at the fuel pump connector E-26.
(1) Disconnect connector E-26 and measure at the harness side.
(2) Check for the continuity between terminal 2 and ground.
- There should be continuity (0 ohms).
If all checks above meet the specifications, go to Step 4. If any check above does not meet the specifications, check the intermediate connector E-44 and repair or replace as needed. Refer to Harness Connector Inspection. If the intermediate connector E-44 is in good condition, repair the harness wire between the fuel pump connector E-26 and the ground. Then confirm that the malfunction symptom is eliminated.




STEP 4. Check the harness wire between the fuel pump check connector A-38 and the fuel pump connector E-26.

NOTE: After inspecting the intermediate connectors C-16 and E-44, inspect the wire. If the intermediate connectors C-16 and E-44 are damaged, repair or replace them. Refer to Harness Connector Inspection. Then confirm a that the malfunction symptom is eliminated.




If the wire between the fuel pump check connector A-38 and the fuel pump connector E-26 is not damaged, replace the fuel pump.
If the wire between the fuel pump check connector A-38 and the fuel pump connector E-26 is damaged, repair it.
Then confirm that the malfunction symptom is eliminated.

STEP 5. Check the fuel pump relay.
(1) Remove the fuel pump relay.




(2) Check for the continuity between the fuel pump relay terminals 2 and 4.
- There should be continuity (approximately 70 ohms).
(3) Use jumper wires to connect fuel pump relay terminal 4 to the positive battery terminal and terminal 2 to the negative battery terminal.




(4) Check the continuity between the fuel pump relay terminals 1 and 3 while connecting and disconnecting the jumper wire at the negative battery terminal.
- There should be continuity (0 ohms) when the jumper wire is connected to the battery terminal and there is no continuity when it is disconnected.
(5) Install the fuel pump relay.
If all checks above meet the specifications, go to Step 6. If any check above does not meet the specifications, replace the fuel pump relay. Then confirm that the malfunction symptom is eliminated.




STEP 6. Check the power supply line at the fuel pump relay connector C-60.
(1) Disconnect connector C-60 and measure at the harness side.
(2) Turn the ignition switch "ON."
(3) Connect terminal 3 and ground and terminal 4 and ground via a 20-ohms resistor,
Measure the current at this time.
- The current should be 0.5 ampere or more.
(4) Turn the ignition switch "OFF."
If within specifications, go to Step 7.
If not within specifications, repair the harness wire and connector between the fuel pump relay and the ignition switch. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.




STEP 7. Check the circuit at the ECM connector C-51.
(1) Disconnect connector C-51 and measure at the harness side.
(2) Turn the ignition switch "ON."
(3) Connect the terminal 8 and ground via a 20-ohms resistor. Measure the current at this time.
- The current should be 0.14 ampere or more.
(4) Turn the ignition switch "OFF."
If within specifications, go to Step 8.
If not within specifications, repair the harness wire between the ECM connector C-51 and the fuel pump relay connector C-60. Then confirm that the malfunction symptom is eliminated.







STEP 8. Check the harness wire between the fuel pump check connector A-38 and the fuel pump relay connector C-60.
If the wire between the fuel pump check connector A-38 and the fuel pump relay connector C-60 is not damaged, go to Step 9.
If the wire between the fuel pump check connector A-38 and the fuel pump relay connector C-60 is damaged, repair it. Then confirm that the malfunction symptom is eliminated.




STEP 9. Check harness connector C-51 at the ECM for damage.
If harness connector C-51 is damaged, repair or replace it. Refer to Harness Connector Inspection.
If harness connector C-51 is in good condition, replace the ECM.
Then confirm that the malfunction symptom is eliminated.
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