Gidday from Perth WA.

I have a problem with the fuel injection and need a wiring diagram or some help if possible.
Trying to work out where the signal comes from, I think it comes from the distributor but I'm having trouble following the wires.


Peekay

DESCRIPTION
The engine management system used on the 4G64 2.4 litre engine incorporates multi-point fuel injection
and ignition control.
The central component of this system is the electronic control unit (ECU). The ECU is a microcomputer which
controls the amount of fuel injected according to signals received from various sensors. As changes are detected in engine speed and load, coolant temperature, air temperature and throttle position, the ECU alters the fuel injection and ignition timing to achieve optimum engine efficiency and fuel economy under those conditions.
The ECU is also capable of performing a self diagnosis to help locate faults in certain circuits in the system.
When a fault occurs, the Check Engine warning lamp on the instrument panel will illuminate and the ECU will memorise the circuit in which the fault occurred.
If a fault occurs in certain components or circuits, the ECU will bypass the fault and substitute a signal from memory, allowing near normal operation of the system until the cause of the fault is rectified.
In the fuel injection system, a metered amount of fuel is injected into the air stream at the inlet ports of the cylinder head and enters the combustion chamber via the inlet valves. The amount of fuel injected is controlled by the time the injectors remain open. The basic time the injectors remain open is determined by the ECU which calculates information from the air flow meter and the distributor. The basic injection time is then modified by the control unit to give optimum engine efficiency and fuel economy for the given conditions according to information received from various other sensors.
The electronic ignition system consists of a distributor and an ignition coil. The distributor has two functions; to provide the ECU with information on engine speed and to distribute secondary voltage to the spark plugs. The secondary voltage (high voltage) is produced by the ignition coil and is dependent on signals from the ECU via a transistor.
The fuel is supplied under pressure by a high pressure electric fuel pump which is mounted inside the fuel
tank. The fuel is maintained at a constant pressure, relevant to variations in manifold vacuum, by the fuel pressure regulator. Excess fuel is returned to the fuel tank via the fuel return line.
The throttle body is located on the inlet manifold and controls the amount of air entering the engine bv action of the throttle valve. Idle speed control is achieved through a reversible electric motor which acts directly on the throttle linkage.
The ECU is mounted in the door pillar adjacent to the drivers’ seat.
Efficient operation of the EFI system depends on Accurate signals being received by the ECU and controlled air flow beyond the air flow meter. Therefore, it is essential that all air, fuel and electrical connections are clean and secure.
Due to the use of complex electronic components in the engine management system and the need for specialist test equipment, diagnosis and testing should only be performed by an authorised dealer.

DEPRESSURISING FUEL SYSTEM
The fuel system should be depressurised before disconnecting any fuel lines or removing any components of the fuel supply system.
1. With the engine idling, disconnect the fuel pump wiring connector.
2. When the engine stalls, operate the starter two or three times.
3. Turn the ignition Off and connect the fuel pump wiring.

FUEL PRESSURE CHECK
Vacuum to the fuel pressure regulator is controlled by the pressure regulator solenoid valve. When the engine is started and the engine coolant temperature is above 90'C or the air temperature is above 50"C, vacuum to the pressure regulator is cut for a period of time to increase the fuel pressure and reduce fuel vaporisation at the injectors.
1. Depressurise the fuel system as previously described.
2. Install a 600 kPa pressure gauge to the fuel rail inlet union using a banjo fitting and a long union bolt.
3. Using a jumper lead, apply battery voltage to the fuel pump test connector and check for fuel leaks with the fuel pump running. Disconnect the jumper lead from the test connector.
4. Start the engine and check that the fuel pressure at idle is approximately 188 kPa.
5. If the fuel pressure is low, check the fuel lines, fuel pressure regulator, fuel filter and fuel pump for blockage, leaks and satisfactory operation.
6. If the fuel pressure is high, disconnect the wiring from the fuel pressure regulator solenoid. If the fuel pressure remains high, check for a blocked return line or a faulty fuel pressure regulator.
7. Disconnect the vacuum hose from the fuel pressure regulator and check that the fuel pressure increases to 250 -260kPa. If the fuel pressure is higher than specified, renew the fuel pressure regulator.
8. Connect the vacuum hose to the fuel pressure regulator and, with the engine idling, quickly open the throttle and check that the fuel pressure increases immediately.
9. Stop the engine and check that the fuel pressure remains constant for two minutes.
10. If the fuel pressure continues to drop, clamp the return line closed. If the fuel pressure now remains steady, renew the fuel pressure regulator. If the fuel pressure continues to drop, check the fuel system for internal and external leaks. If no leaks are present, renew the fuel pump.
11. Depressurise the fuel system and disconnect the fuel pressure gauge.

FUEL TANK
Removal, installation
1. Disconnect the negative battery terminal.
2. Remove the fuel tank drain plug and drain the fuel into a container. Install and tighten the plug when draining is complete.
3. Disconnect the fuel pump and fuel gauge sender unit wiring connectors.
4. Disconnect the fuel and vent hoses leading to the fuel tank.
5. Support the fuel tank and remove the fuel tank retaining nuts.
6. Lower the fuel tank and withdraw it from the vehicle.

Installation is a reversal of the removal procedure with attention to the following points:
1. Ensure that the wiring and hoses are securely connected.
2. Fill the fuel tank with fuel and check for leaks.

FUEL PUMP
Testing
1. Connect a jumper lead between the positive battery terminal and the fuel pump test connector. Lightly squeeze the fuel return hose at the fuel pressure regulator and check that fuel flow can be felt through the hose. It should also be possible to the hear the fuel pump operating at the fuel cap opening.
2. If the fuel pump does not operate, disconnect the fuel pump wiring connector and check for continuity between the fuel pump terminals. If continuity is not available, renew the fuel pump.
3. Check the control relay as described later in this chapter.
Removal, installation
1. Remove the fuel tank as follows:
a. Disconnect the negative battery terminal.
b. Remove the fuel tank drain plug and drain the fuel into a container.
c. Disconnect the fuel pump and fuel gauge sender unit wiring connectors.
d. Disconnect the fuel and vent hoses leading to the fuel tank.
e. While supporting the fuel tank, remove the fuel tank retaining nuts. Lower the fuel tank and withdraw it from the vehicle.
2. Remove the fuel pump retaining nuts and withdraw the fuel pump from the fuel tank. Discard the gasket.

Installation is a reversal of the removal procedure with attention to the following points:
1. Check that the fuel pump inlet filter is clean.
2. Ensure that a new fuel pump gasket is installed and tighten the fuel pump retaining nuts securely.
3. Securely connect the wiring and the fuel hoses.
4. Install the fuel tank and check that all hose and wiring connections are secure.
5. Check for fuel leaks after starting the engine.

PRESSURE REGULATOR SOLENOID VALVE
Testing
1. Disconnect the wiring and measure the resistance between the pressure regulator solenoid terminals.
The resistance should be 36 - 46 ohms at 20"C.
2. Using jumper leads, connect the solenoid terminals to the battery and apply vacuum to the centre port of the solenoid valve. Vacuum should be retained. Disconnect the jumper leads and check that vacuum is released.
3. With the ignition On, check for battery voltage at the solenoid connector black/red wire terminal.

OXYGEN SENSOR
Testing
1. Run the engine until the normal operating temperature is attained. (80 - 90'C).
2. Disconnect the oxygen sensor wiring connector and connect a digital voltmeter between the oxygen sensor terminal and earth.
3. With the engine running, quickly open and close the throttle fully several times and check that the voltage increases to approximately 1 volt. If the voltage is not as specified, refer the vehicle to an authorised dealer for further diagnosis.

CONTROL RELAY
Removal, testing
1. Open the glove compartment, remove the retaining screws and remove the glove compartment and lid.
2. Disconnect the wiring from the control relay.
3. Remove the retaining screw and withdraw the relay from the vehicle. 4. Check that continuity exists between the following relay terminals:
3 and 5 - approximately 95 ohms
2 and 5 - approximately 95 ohms
6 and 7 - approximately 35 ohms
6 and 8 - one direction only
5. Using jumper leads, connect terminals 6 and 7 to the battery terminals and check that continuity exists between terminals 1 and 4.
6. Using jumper leads, connect terminals 6 and 8 to the battery terminals and check that continuity exists between terminals 2 and 4.

Fuel and Engine Management Troubleshooting Chart p95-97 available as pdf file.
Complete Wiring Harness Diagram & Colour Codes p180, 181 available as pdf.
E-mail me direct to miris@orcon.net.nz if you need them please, Mike.

Thanks Mike,
I didn't think it would be that complicated, I thought the distributor was the only component sending a signal.
The problem I have is that No 3 injector is not opening and as I have swapped No 1 & No 3 over it proves that it's not the injector.
When the motor is running I can't get to the wiring at the injector to check for a signal, if I could trace the wire back i might be able to test it elsewhere.
All it would take is a bad earth to cause the problem I guess.

Peekay

hi there ...

Im having a problem with high fuel consuption with my 89 L300 2.4 ... when i start the engine the RPM gauge doesnt goes over 400\200 Rpm ... and its fuel consuption is very high ... on a full tank 45 ltr i cant make more then 190 km on highway ... and driving around town its consuption its around 100\120 km ... and if the Rpm gouge gets to 1000 rpm its starts choking

Can anyone help me ... i have changed air filter, fuel filter and spark plugs ... i actualy dont know what else i can do to sort this out.

Tks in advance

chris