Engine Controls - System & Component Testing: Diagnosis Land Rover Discovery II

Fuel Pressure Test (Discovery)

Note. Regulated fuel pressure should be 35-37 psi (2.4-2.6 kg/cm 2 ) with engine at idle. Pressure will vary depending on amount of intake manifold vacuum acting on fuel pressure regulator.

1. Ensure engine temperature is less than normal operating temperature. If engine is at normal operating temperature, there may be abnormal pressure readings because of hot-soak fuel vaporization. Removing fuel filler cap may reduce effect of fuel vaporization. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-3175-S42666925572004012700000) . Install fuel pressure gauge to fuel rail. Install shut-off valves in fuel supply and return lines. Activate fuel pump and bleed air from fuel pressure gauge.
2. Allow fuel pressure to stabilize and record fuel pressure. Turn fuel pump off and monitor gauge for changes in fuel pressure. If fuel pressure does not change, go to «FUEL INJECTOR BALANCE CHECK»(ref-3175-S31790216852000041800000) . If fuel pressure decreases, close shut-off valve on fuel supply line and check fuel pressure. If fuel pressure decreases, go to next step. If fuel pressure does not decrease, check valve in fuel pump is faulty. Replace fuel pump.
3. If fuel pressure continues to decrease, close shut-off valve on fuel return line and check fuel pressure. If fuel pressure does not decrease, replace fuel pressure regulator. If fuel pressure continues to decrease, check fuel system for a leak. Repair as necessary. If no leaks are found, one or more fuel injectors may be leaking. Go to «FUEL INJECTOR BALANCE CHECK»(ref-3175-S31790216852000041800000) .

Fuel Pressure Test (Discovery Series II & Range Rover)

Note. Regulated fuel pressure should be 50 psi (3.5 kg/cm 2 ) with engine at idle.

Fuel pump delivery pressure and pressure regulator operating pressure can be checked using a Schraeder type valve located at the rear of the engine on the fuel rail. The valve allows the pump delivery pressure to be measured using a suitable gauge and an adaptor and hose. If fuel pressure is not as specified at engine idle, ensure fuel line is not pinched, crushed or damaged and that there are no loose or leaking connections. If fuel lines are okay, replace fuel pump/sending unit assembly.

Fuel Injector Balance Test

1. Ensure engine temperature is less than normal operating temperature. If engine is at normal operating temperature, there may be abnormal pressure readings because of hot-soak fuel vaporization. Removing fuel filler cap may reduce effect of fuel vaporization. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-3175-S42666925572004012700000) . Install fuel pressure gauge to fuel rail.
2. Connect fuel injector tester to No. 1 injector. Connect tester Red lead to battery positive terminal and Black lead to battery negative terminal. Activate fuel pump and bleed air from fuel pressure gauge. Turn fuel pump off and allow fuel pressure to stabilize. Record stabilized fuel pressure. Set fuel injector tester for a 500 mS pulse.
3. Using fuel injector tester, trigger fuel injector No. 1 and record stabilized fuel pressure. Move tester to fuel injector No. 2. Turn fuel pump on and allow fuel pressure to stabilize. Record stabilized fuel pressure. Trigger fuel injector No. 2 and record stabilized fuel pressure. Repeat procedure for remaining fuel injectors, recording fuel pressures before and after triggering each fuel injector. Ensure fuel system is pressurized before triggering each fuel injector.
4. Compare injector pressure drop for all injectors to the average pressure drop. Injector pressure drop is the difference between recorded pressures before and after fuel injector is triggered. For example, if the pressure before the injector is triggered is 30 psi and after is 16 psi, the injector pressure drop will be 14 psi. Add pressure drop values for all 8 injectors and divide by 8 to obtain the average fuel injector pressure drop.
5. The pressure drop for each injector should be within 2 psi (more or less than) of the average injector pressure drop. For example, if the average fuel pressure drop is 14 psi, then the injector pressure drop for each injector could be 12-16 psi.
6. Closely monitor injector pressure drop on each cylinder that has a misfire. If an injector is clogged or restricted, the injector pressure drop will be more than 2 psi greater (i.e.: more than 16 psi) than the average. If the injector is allowing to much fuel or is leaking, the injector pressure drop will be more than 2 psi less (i.e.: less than 12 psi) than the average. Replace any injector with a fuel pressure drop more than 2 psi greater or less than the average pressure drop. If pressure drop for all injectors are within 2 psi of the average, go to «FUEL INJECTOR ELECTRICAL CHECK»(ref-3175-S14105990632000041800000) .

Fuel Injector Electrical Test

1. Using a backprobe set, connect Snap-On Personal Automotive Computer (PAC) tester to suspect fuel injector driver terminal. See «IDENTIFYING FUEL INJECTOR DRIVER CONNECTOR TERMINALS (GEMS)»(ref-3175-S41483341422000041800000) or «IDENTIFYING FUEL INJECTOR DRIVER CONNECTOR TERMINALS (BOSCH)»(ref-3175-S05473603582000041800000) table. Set Snap-On PAC tester to 100 volt scale and 5.0 mS. Start engine and allow it to idle. Compare fuel injector wave pattern with known-good wave pattern. (Scheme 19)
2. If injector coil release spikes average approximately 80 volts, go to next step. An injector coil with a short will have average coil release spikes lower than 80 volts. Replace faulty fuel injector if coil release spikes average less than 80 volts.
3. Reset Snap-On PAC tester to 50 volt scale. Start engine and allow to idle. Check "On" time voltage for each injector. If "On" time voltage is constant at one volt or less, fuel injector drivers are operating properly. If "On" time voltage is not constant at one volt or less, go to next step.
4. If "On" time voltage is more than one volt, injector driver is not providing a consistent ground for the injector coil. Check for poor connections or loose wires between suspect fuel injector and ECM. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). Perform repairs as necessary. If no problems are found, substitute a known-good ECM and recheck for original symptom or indication. If symptom or indication goes away, replace original ECM.

IDENTIFYING FUEL INJECTOR DRIVER CONNECTOR TERMINALS (GEMS)

IDENTIFYING FUEL INJECTOR DRIVER CONNECTOR TERMINALS (BOSCH)

Scheme 19

EVAP System Pressure Test

1. Ensure fuel filler cap is properly installed. Using Land Rover TestBook (use diagnostic disc DRG0002), close EVAP canister vent solenoid. Connect EVAPS Diagnostic Station System (LRA-19-004) to vehicle according to manufacturer instructions. Install Service Port Adapter (LRA-19-004-1) to line from fuel vapor separator, at EVAP canister. Connect EVAP diagnostic station Red hose to service port adapter. (Scheme 20)
2. Open valve on nitrogen cylinder. Turn control panel valve to PRESSURE position and pressurize EVAP system to 14.5 in. H2O. Turn control panel valve to OFF/HOLD position and monitor pressure gauge for 2 minutes. If pressure decrease is less than 6 in. H2O within 2 minutes, system is okay at this time. Go to step 4. If pressure decrease is more than 6 in. H2O within 2 minutes, go to next step.
3. Turn control panel valve to PRESSURE position and pressurize EVAP system to 30.0 in. H2O. Using an ultrasonic leak detector, check all system hoses, connections and joints for leaks. Repair as necessary and repeat EVAP system pressure test. When pressure test is completed, go to next step.
4. Insert Blue pressure release hose into pressure exhaust evacuation pipe. Turn control panel valve to PRESSURE RELEASE position. Using TestBook, open EVAP canister vent solenoid. Monitor pressure gauge until EVAP system pressure is zero inches of H2O. Turn control panel valve to OFF/HOLD position and close nitrogen cylinder valve. When repairs are completed, perform «EVAP SYSTEM PRESSURE TEST DRIVE CYCLE»(ref-3175-S26651192592000041800000).

EVAP System Pressure Test Drive Cycle

1. Turn ignition on for 30 seconds. Ensure Engine Coolant Temperature (ECT) is less than 140°F (60°C).
2. Start engine and allow to idle for 2 minutes. Perform 2 light accelerations from zero to 35 MPH using light pedal pressure and slow to a stop. Perform 2 medium accelerations from zero to 45 MPH using moderate pedal pressure and slow to a stop. Perform 2 hard accelerations from zero to 55 MPH using heavy pedal pressure.
3. When second acceleration cycle is completed, increase vehicle speed to 60 MPH and continue for 5 minutes. Reduce speed to 50 MPH and continue for 5 minutes. Reduce speed to 35 MPH, continue for 5 minutes and slow to a stop.
4. Allow engine to idle for 2 minutes. Check for DTCs using Land Rover TestBook or OBD-II scan tool. If any DTC is indicated, perform specified repairs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table in appropriate SELF-DIAGNOSTICS article. If no DTCs are indicated, repair is complete.

Scheme 20

1. Ensure fuel filler cap is properly installed. Using Land Rover TestBook confirm that DTCs displayed relate to an EVAP system fault. Inspect components in fuel and EVAP system for damage or poor connections. (Scheme 21)or (Scheme 22). Repair or replace components as necessary. Reset Malfunction Indicator Lamp (MIL) using TestBook.
2. Perform Drive Cycle. See «EVAP SYSTEM PRESSURE TEST DRIVE CYCLE»(ref-3175-S03159676792000041800000). Using TestBook confirm that the Evaporative Loss Control (ELC) Inspection and Maintenance (IM) flag has cleared. This procedure should confirm that the ELC test was carried out during the drive cycle and that the fault was corrected.
3. If the IM flag is still indicated, use TestBook to check for a DTC is set or IM flag is still indicated, but no DTCs are set. If a DTC is set, perform DTC inspection and appropriate repairs. If a IM flag is still indicated, but no DTCs are set the conditions for the ELC check have not been met and the drive cycle must be repeated. Connect the EVAP Diagnostic Station to the service port and carry out the procedures given in the operating instructions supplied with the equipment. Perform repairs as indicated by the EVAP Diagnostic Station and repeat step 2.

1. Switch ignition on for 30 seconds. Ensure engine coolant temperature is less than 140°F (60°C). Start the engine and allow to idle for 2 minutes.
2. Perform 2 light accelerations, 0-35 mph, with light pedal pressure. Perform 2 medium accelerations, 0-45 mph, with moderate pedal pressure. Perform 2 hard accelerations, 0-55 mph, with heavy pedal pressure.
3. Increase speed to 60 mph and cruise for 8 minutes. Decrease speed to 50 mph and cruise for 3 minutes. Allow engine to idle for 3 minutes. Connect Testbook and check for DTCs.

Scheme 21

Scheme 22