1) The document describes the fuel system diagnosis procedure for an engine. It details the circuit, provides a test description, and lists diagnostic steps to locate issues with low or high fuel pressure.
2) The diagnostic table guides the user through a step-by-step process to test the fuel pump, fuel lines, fuel pressure regulator, fuel injectors, and other components to diagnose problems like leaks, vacuum restrictions, or faulty parts that cause improper fuel pressure.
3) Issues with low fuel pressure could be caused by leaks, a faulty fuel pump, fuel pressure regulator, or fuel injectors. High fuel pressure may result from a stuck open fuel pressure regulator. The diagnostic procedure helps methodically test each component
1) The document describes the fuel system diagnosis procedure for an engine. It details the circuit, provides a test description, and lists diagnostic steps to locate issues with low or high fuel pressure.
2) The diagnostic table guides the user through a step-by-step process to test the fuel pump, fuel lines, fuel pressure regulator, fuel injectors, and other components to diagnose problems like leaks, vacuum restrictions, or faulty parts that cause improper fuel pressure.
3) Issues with low fuel pressure could be caused by leaks, a faulty fuel pump, fuel pressure regulator, or fuel injectors. High fuel pressure may result from a stuck open fuel pressure regulator. The diagnostic procedure helps methodically test each component
1) The document describes the fuel system diagnosis procedure for an engine. It details the circuit, provides a test description, and lists diagnostic steps to locate issues with low or high fuel pressure.
2) The diagnostic table guides the user through a step-by-step process to test the fuel pump, fuel lines, fuel pressure regulator, fuel injectors, and other components to diagnose problems like leaks, vacuum restrictions, or faulty parts that cause improper fuel pressure.
3) Issues with low fuel pressure could be caused by leaks, a faulty fuel pump, fuel pressure regulator, or fuel injectors. High fuel pressure may result from a stuck open fuel pressure regulator. The diagnostic procedure helps methodically test each component
1) The document describes the fuel system diagnosis procedure for an engine. It details the circuit, provides a test description, and lists diagnostic steps to locate issues with low or high fuel pressure.
2) The diagnostic table guides the user through a step-by-step process to test the fuel pump, fuel lines, fuel pressure regulator, fuel injectors, and other components to diagnose problems like leaks, vacuum restrictions, or faulty parts that cause improper fuel pressure.
3) Issues with low fuel pressure could be caused by leaks, a faulty fuel pump, fuel pressure regulator, or fuel injectors. High fuel pressure may result from a stuck open fuel pressure regulator. The diagnostic procedure helps methodically test each component
10. If there is fuel bleeding back through the fuel return Circuit Description outlet, this is due to a faulty fuel pressure regulator. The fuel pump is an in–tank fuel pump mounted to a fuel 14. Another symptom often present when the fuel injec- sender assembly. The fuel pump will remain on as long as tors are leaking is hard starting. Leaking fuel injec- the engine is cranking or running and the powertrain con- tors can cause a flooding condition. trol module (PCM)/engine control module (ECM) is receiv- 23. Fuel leaking from the fuel pump inlet is due to a ing reference pulses from the crankshaft position (CKP) faulty one–way check valve in the fuel pump. sensor. If there are no reference pulses, the PCM/ECM will turn off the fuel pump 2 seconds after the ignition CAUTION : The fuel system is under pressure. To switch is turned ON or 2 seconds after the engine stops avoid fuel spillage and the risk of personal injury or running. The fuel pump delivers fuel to the fuel rail and the fire, it is necessary to relieve the fuel system pressure fuel injectors, where the fuel system pressure is controlled before disconnecting the fuel lines. from 284 to 325 kPa (41 to 47 psi) by the fuel pressure reg- CAUTION : Do not pinch or restrict nylon fuel lines to ulator. The excess fuel is returned to the fuel tank. avoid damage that could cause a fuel leak, resulting in possible fire or personal injury. Test Description The number(s) below refer to step(s) on the diagnostic table. Fuel Pressure Relief Procedure 1. Remove the fuel cap. 2. When the engine is idling, the intake manifold vacu- 2. Remove the fuel pump fuse EF18 from the engine um is high. This vacuum is applied to the fuel pres- fuse box. sure regulator diaphragm, offsetting the spring 3. Start the engine and allow the engine to stall. pressure inside the fuel pressure regulator and low- 4. Crank the engine for an additional 10 seconds. ering the fuel pressure.
Fuel System Diagnosis
Step Action Value(s) Yes No
1 1. Relieve the fuel system pressure. 284–325 kPa Go to Step 2 Go to Step 5 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel pressure within the values specified and holding steady? 2 1. Disconnect the fuel pressure regulator vacuum System OK Go to Step 3 hose. 2. Start the engine. 3. Allow the engine to idle. 4. Connect the fuel pressure regulator vacuum hose. Does the fuel pressure decrease? 3 1. Allow the engine to idle. Go to Step 4 Go to Step 16 2. Disconnect the vacuum hose from the fuel pressure regulator. 3. Connect a vacuum pump with a gauge to the fuel pressure regulator vacuum port. 4. Apply 41–47 kPa (12–14 in. Hg) of vacuum to the fuel pressure regulator. Does the fuel pressure decrease? 4 1. Locate and correct the cause of the vacuum System OK restriction to the fuel pressure regulator. 2. Confirm the operation of the fuel pressure reg- ulator. Is the repair complete?
DAEWOO V–121 BL4
1F – 50IENGINE CONTROLS
Step Action Value(s) Yes No
5 1. Relieve the fuel system pressure. 284–325 kPa Go to Step 6 Go to Step 17 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel pressure within the values specified but not holding steady? 6 Inspect the fuel lines for a leak. Go to Step 7 Go to Step 8 Is the problem found? 7 1. Replace the fuel line(s) as needed. 284–325 kPa System OK 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel pressure within the values specified but not holding steady? 8 1. Remove the fuel pump assembly. Go to Step 9 Go to Step 10 2. With the fuel pump under pressure, inspect the fuel pump coupling hoses for leaking. Is the problem found? 9 1. Tighten or replace the fuel pump coupling 284–325 kPa System OK hoses as needed. (41–47 psi) 2. Install a fuel pressure gauge. 3. Turn the ignition ON. Is the fuel pressure within the values specified but not holding steady? 10 With the fuel system under pressure, inspect the fuel Go to Step 11 Go to Step 12 return outlet for leaking. Is the problem found? 11 1. Replace the fuel pressure regulator. 284–325 kPa System OK 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel pressure within the values specified but not holding steady? 12 With the fuel system under pressure, inspect the fuel Go to Step 13 Go to Step 14 inlet for leaking. Is the problem found? 13 1. Replace the fuel pump assembly. 284–325 kPa System OK 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel pressure within the values specified but not holding steady? 14 1. Remove the fuel rail and the fuel injectors as Go to Step 15 an assembly. 2. With the fuel system under pressure, inspect all of the fuel injectors for leaking. Is the problem found? 15 1. Replace the leaking fuel injector(s). 284–325 kPa System OK 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel pressure within the values specified but not holding steady?
DAEWOO V–121 BL4
ENGINE CONTROLS 1F – 51
Step Action Value(s) Yes No
16 1. Replace the fuel pressure regulator. System OK 2. Disconnect the fuel pressure regulator vacuum hose. 3. Start the engine. 4. Allow the engine to idle. 5. Connect the fuel pressure regulator vacuum hose. Does the fuel pressure decrease? 17 1. Relieve the fuel system pressure. 284–325 kPa Go to Step 13 Go to Step 18 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel system pressure below the values speci- fied and holding steady? 18 1. Relieve the fuel system pressure. 284–325 kPa Go to Step 19 2. Install a fuel pressure gauge. (41–47 psi) 3. Turn the ignition ON. Is the fuel system pressure below the values speci- fied and holding steady? 19 Inspect the fuel lines for leaks. Go to Step 7 Go to Step 20 Is the problem found? 20 1. Remove the fuel pump assembly. Go to Step 9 Go to Step 21 2. With the fuel pump under pressure, inspect the fuel pump coupling hoses for leaking. Is the problem found? 21 1. Remove the fuel pump assembly. Go to Step 11 Go to Step 22 2. With the fuel system under pressure, inspect the fuel return outlet for leaking. Is the problem found? 22 1. Remove the fuel pump assembly. Go to Step 13 Go to Step 23 2. With the fuel system under pressure, inspect the fuel inlet for leaking. Is the problem found? 23 1. Remove the fuel rail and the fuel injectors as Go to Step 15 Go to Step 13 an assembly. 2. With the fuel system under pressure, inspect all of the fuel injectors for leaking. Is the problem found?
DAEWOO V–121 BL4
1F – 52IENGINE CONTROLS
FUEL PUMP RELAY CIRCUIT CHECK
tion, rubbed through wire insulation, or a broken wire in- Circuit Description side the insulation. When the ignition switch is turned ON, the powertrain con- Test Description trol module (PCM)/engine control module (ECM) will acti- vate the fuel pump relay and run the in–tank fuel pump. The number(s) below refer to step(s) on the diagnostic The fuel pump will operate as long as the engine is crank- table. ing or running and the PCM/ECM is receiving ignition ref- 3. This step checks for the PCM/ECM providing a erence pulses. ground for the operation of the fuel pump relay. 7. By confirming that the wiring is OK using Steps 2 If there are no reference pulses, the PCM/ECM will shut through 6, it can be determined that the fuel pump off the fuel pump within 2 seconds after the ignition switch relay is at fault. is turned ON. 9. After determining that there is no ground being pro- vided by the PCM/ECM to the fuel pump relay, the Diagnostic Aids fault is either the PCM/ECM or the wiring between An intermittent problem may be caused by a poor connec- the PCM/ECM and the fuel pump relay.
DAEWOO V–121 BL4
ENGINE CONTROLS 1F – 53
Fuel Pump Relay Circuit Check
Step Action Value(s) Yes No 1 1. Turn the ignition OFF for 10 seconds. 2 sec System OK Go to Step 2 2. Turn the ignition ON. 3. Listen for in–tank fuel pump operation. Does the fuel pump operate for the time specified? 2 1. Turn the ignition OFF. Go to Step 3 Go to Step 8 2. Disconnect the fuel pump relay. 3. Connect a test light between the fuel pump relay connector terminal 86 and battery posi- tive. 4. Turn the ignition ON. Is the test light on? 3 1. Turn the ignition OFF. 2 sec Go to Step 4 Go to Step 9 2. Connect a test light between the fuel pump relay connector terminal 85 and battery posi- tive. 3. Turn the ignition ON. 4. With the ignition ON, the test light should light for the time specified. Is the test light on? 4 1. Turn the ignition OFF. Go to Step 5 Go to Step 11 2. Connect a test light between the fuel pump relay connector terminal 30 and ground. Is the test light on? 5 Check for an open or short to ground in the wire be- Go to Step 6 Go to Step 7 tween the fuel pump relay connector terminal 87 and the fuel cutoff switch terminal 1. Is the problem found? 6 1. Repair the wire between the fuel pump relay 2 sec System OK connector terminal 87 and the fuel cutoff switch terminal 1. 2. Install the fuel pump relay. 3. Turn the ignition OFF for 10 seconds. 4. Turn the ignition ON. Does the fuel pump operate for the time specified? 7 1. Replace the fuel pump relay. 2 sec System OK 2. Turn the ignition OFF for 10 seconds. 3. Turn the ignition ON. Does the fuel pump operate for the time specified? 8 Check for an open wire between the fuel pump relay Go to Step 13 Go to ”Ignition connector terminal 86 and the ignition 1 relay con- 1 Relay Circuit nector terminal 86. Check” Is the problem found? 9 Check for an open wire between the fuel pump relay Go to Step 10 Go to Step 12 connector terminal 85 to the powertrain control mod- ule (PCM)/engine control module (ECM) connector terminal E13. Is the problem found?
DAEWOO V–121 BL4
1F – 54IENGINE CONTROLS
Step Action Value(s) Yes No
10 1. Repair the wire between the fuel pump relay 2 sec System OK connector terminal 85 to the PCM/ECM con- nector terminal E13. 2. Install the fuel pump relay. 3. Turn the ignition OFF for 10 seconds. 4. Turn the ignition ON. Does the fuel pump operate for the time specified? 11 1. Repair the wire between the fuel pump relay 2 sec System OK connector terminal 30 and the battery. 2. Install the fuel pump relay. 3. Turn the ignition OFF for 10 seconds. 4. Turn the ignition ON. Does the fuel pump operate for the time specified? 12 1. Replace the PCM/ECM. 2 sec System OK 2. Turn the ignition OFF for 10 seconds. 3. Turn the ignition ON. Does the fuel pump operate for the time specified? 13 Repair the wire between the fuel pump relay connec- System OK tor terminal 86 and the ignition 1 relay connector ter- minal 86. Is the repair complete?