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
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.
NG -- PERFORM ACTIVE TEST USING TECHSTREAM (OPERATE CIRCUIT OPENING RELAY)
OK -- Continue to next step.
2. INSPECT FUEL PUMP RELAY ASSEMBLY
(a) Remove the fuel pump relay from the engine room relay block.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(c) Reinstall the fuel pump relay.
NG -- REPLACE FUEL PUMP RELAY ASSEMBLY
OK -- Continue to next step.
3. INSPECT FUEL PUMP RESISTOR (RESISTANCE)
(a) Inspect the fuel pump resistor resistance.
(1) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPLACE FUEL PUMP RESISTOR
OK -- Continue to next step.
4. 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 relay block.
(2) Disconnect the fuel pump resistor connector.
(3) Measure the resistance according to the value(s) in the table below.
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 fuel pump resistor connector.
(2) Disconnect the fuel pump connector.
(3) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
(4) Reconnect the fuel pump resistor connector.
(5) Reconnect the fuel pump connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- PROCEED TO NEXT SUSPECTED AREA SHOWN ON PROBLEM SYMPTOMS TABLE
5. PERFORM ACTIVE TEST USING TECHSTREAM (OPERATE CIRCUIT OPENING RELAY)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON and turn the Techstream 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 Techstream.
OK:
Operating sounds can be heard from relay.
NG -- INSPECT CIRCUIT OPENING RELAY
OK -- Continue to next step.
6. INSPECT ECM POWER SOURCE CIRCUIT
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
7. INSPECT FUEL PUMP RELAY ASSEMBLY
(a) Remove the fuel pump relay from the engine room relay block.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(c) Reinstall the fuel pump relay.
NG -- REPLACE FUEL PUMP RELAY ASSEMBLY
OK -- Continue to next step.
8. INSPECT FUEL PUMP ASSEMBLY
(a) Inspect the fuel pump resistance.
(1) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(b) Inspect the fuel pump operation.
(1) Apply battery voltage to both terminals. Check that the pump operates.
CAUTION:
- 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.
9. 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 fuel pump connector.
(2) Remove the fuel pump relay from the engine room relay block.
(3) Measure the resistance according to the value(s) in the table below.
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) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
(3) Reconnect the fuel pump connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
10. CHECK HARNESS AND CONNECTOR (CIRCUIT OPENING RELAY - FUEL PUMP RELAY)
(a) Remove the circuit opening relay from the engine room relay block.
(b) Remove the fuel pump relay from the engine room relay block.
(c) Measure the resistance according to the value(s) in the table below.
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 OR CONNECTOR (EFI RELAY - CIRCUIT OPENING RELAY)
11. INSPECT CIRCUIT OPENING RELAY
(a) Remove the circuit opening relay from the engine room relay block.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(c) Reinstall the circuit opening relay.
NG -- REPLACE CIRCUIT OPENING RELAY
OK -- Continue to next step.
12. INSPECT ECM (FC VOLTAGE)
(a) Turn the ignition switch to ON.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
NG -- CHECK AND REPLACE HARNESS OR CONNECTOR (ECM - CIRCUIT OPENING RELAY - IGNITION)
OK -- REPLACE ECM