Fuel Pump Control Circuit
1GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: Fuel Pump Control Circuit
Fuel Pump Control Circuit
DESCRIPTION
As shown in the illustration, when the engine is cranked, current flows from terminal ST1 of the ignition switch into the ECM and the ST (starter) relay coil and also current flows to terminal STA of the ECM (STA signal).
When the STA signal and NE signal are input to the ECM, Tr1 (power transistor 1) is turned ON, current flows to the coil of the circuit opening relay, the relay switches on, power is supplied to the fuel pump, and the fuel pump operates.
While the NE signal is generated (engine running), the ECM keeps the Tr1 ON (circuit opening relay ON) and the fuel pump also keeps operating.
The fuel pump speed is controlled at two levels (high speed or low speed) by engine condition (starting, light load, heavy load). When the engine starts (STA ON), Tr2 (power transistor 2) in the ECM is OFF, so the fuel pump relay closes and positive battery voltage is applied directly to the fuel pump. The fuel pump operates at high speed.
During idling or under light loads, Tr2 goes ON, and then power is supplied to the fuel pump via the fuel pump resistor. The fuel pump operates at low speed.
WIRING DIAGRAM
HINT: This DTC chart is on the premise that the engine is started normally. If the engine is difficult to start, proceed to the problem symptoms table (Symptom Related Diagnostic Procedures).
INSPECTION PROCEDURE
PROCEDURE
1. CHECK FUEL PUMP OPERATION
(a) Check if there is pressure in the fuel inlet hose.
HINT: If there is fuel pressure, you will hear the sound of fuel flowing.
OK -- INSPECT FUEL PUMP RELAY ASSEMBLY
NG -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM (OPERATE CIRCUIT OPENING RELAY)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Fuel Pump / Speed.
(d) Check whether operating sounds can be heard while operating the relay using the tester.
OK:
Operating sounds can be heard from relay.
OK -- INSPECT ECM POWER SOURCE CIRCUIT
NG -- Continue to next step.
3. INSPECT CIRCUIT OPENING RELAY
(a) Remove the circuit opening relay from the engine room R/B.
(b) Check the circuit opening relay resistance.
Standard Resistance:
(c) Reinstall the circuit opening relay.
NG -- REPLACE CIRCUIT OPENING RELAY
OK -- Continue to next step.
4. INSPECT ECM (FC VOLTAGE)
(a) Turn the ignition switch ON.
(b) Measure the voltage between the terminals of the E8 and E6 ECM connectors.
Standard Voltage:
OK -- REPLACE ECM
NG -- CHECK AND REPLACE HARNESS AND CONNECTOR (ECM - CIRCUIT OPENING RELAY - IGNITION)
5. INSPECT ECM POWER SOURCE CIRCUIT
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
6. INSPECT FUEL PUMP RELAY ASSEMBLY
(a) Remove the fuel pump relay from the engine room R/B.
(b) Check the fuel pump relay resistance.
Standard Resistance:
(c) Reinstall the fuel pump relay.
NG -- REPLACE FUEL PUMP RELAY ASSEMBLY
OK -- Continue to next step.
7. INSPECT FUEL PUMP ASSEMBLY
(a) Inspect the fuel pump resistance.
(1) Measure the resistance between terminals 4 and 5.
Standard Resistance:
0.2 to 3.0 Ohms at 20°C (68°F)
(b) Inspect the fuel pump operation.
(1) Apply battery voltage to both terminals. Check that the pump operates.
NOTICE:
- These tests must be done quickly (within 10 seconds) to prevent the coil from burning out.
- Keep the fuel pump as far away from the battery as possible.
- Always do the switching at the battery side.
NG -- REPLACE FUEL PUMP ASSEMBLY
OK -- Continue to next step.
8. CHECK HARNESS AND CONNECTOR (FUEL PUMP - FUEL PUMP RELAY, FUEL PUMP - BODY GROUND)
(a) Check the harness and connector between the fuel pump and fuel pump relay.
(1) Disconnect the F19 fuel pump connector.
(2) Remove the fuel pump relay from the engine room R/B.
(3) Check the resistance.
Standard Resistance (Check for open):
Standard Resistance (Check for short):
(4) Reconnect the fuel pump connector.
(5) Reinstall the fuel pump relay.
(b) Check the harness and connector between the fuel pump and body ground.
(1) Disconnect the fuel pump connector.
(2) Check the resistance.
Standard Resistance (Check for open):
(3) Reconnect the fuel pump connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
9. CHECK HARNESS AND CONNECTOR (CIRCUIT OPENING RELAY - FUEL PUMP RELAY)
(a) Remove the circuit opening relay from the engine room R/B.
(b) Remove the fuel pump relay from the engine room R/B.
(c) Check the resistance.
Standard Resistance (Check for open):
Standard Resistance (Check for short):
(d) Reinstall the circuit opening relay.
(e) Reinstall the fuel pump relay.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK AND REPAIR HARNESS AND CONNECTOR (EFI RELAY - CIRCUIT OPENING RELAY)
10. INSPECT FUEL PUMP RELAY ASSEMBLY
(a) Remove the fuel pump relay from the engine room R/B.
(b) Check the fuel pump relay resistance.
Standard Resistance:
(c) Reinstall the fuel pump relay.
NG -- REPLACE FUEL PUMP RELAY ASSEMBLY
OK -- Continue to next step.
11. INSPECT FUEL PUMP RESISTER (RESISTANCE)
(a) Inspect the fuel pump resistor resistance.
(1) Measure the resistance.
Standard Resistance:
0.70 to 0.76 Ohms at 20°C (68°F)
NG -- REPLACE FUEL PUMP RESISTER
OK -- Continue to next step.
12. CHECK HARNESS AND CONNECTOR (FUEL PUMP RELAY - FUEL PUMP RESISTOR - FUEL PUMP)
(a) Check the harness and connector between the fuel pump relay and fuel pump resistor.
(1) Remove the fuel pump relay from the engine room R/B.
(2) Disconnect the F11 fuel pump resistor connector.
(3) Check the resistance.
Standard Resistance (Check for open):
Standard Resistance (Check for short):
(4) Reinstall the fuel pump relay.
(5) Reconnect the fuel pump resistor connector.
(b) Check the harness and connector between the fuel pump resistor and fuel pump.
(1) Disconnect the F11 fuel pump resistor connector.
(2) Disconnect the fuel pump connector.
(3) Check the resistance.
Standard Resistance (Check for open):
Standard Resistance (Check for short):
(4) Reconnect the fuel pump resistor connector.
(5) Reconnect the fuel pump connector.
NG -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN ON PROBLEM SYMPTOMS TABLE
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR