Fuel Pump, Checking
Fuel Pump, Checking
Checking function and voltage supply --> [ Function and Voltage Supply, Checking ]
Checking fuel pressure --> [ Fuel Pressure, Checking ]
Checking residual pressure --> [ Residual Pressure, Checking ]
Checking fuel delivery --> [ Delivery Rate, Checking ]
Checking current consumption of fuel pump --> [ Delivery Rate, Checking ]
Special tools, testers and auxiliary items required
• Wrench (lock ring removal)
• Remote control connection
• Pressure gauge
• Hose
• Pressure gauge adapter
• Adapter
• Multimeter
Special tools, testers and auxiliary items required
• Torque wrench
• Connector test set
• Voltage tester
• Measuring container
• Wiring diagram
Function and Voltage Supply, Checking
Test conditions
• Battery voltage at least 12.5 V
• Fuse for Fuel Pump (FP) OK.
• Fuel Pump (FP) Control Module (J538) OK.
• Low Fuel Pressure Sensor (G410) OK.
Test sequence
Observe Safety Precautions: --> [ Safety Precautions ] Fuel System
Observe Clean Working Conditions: --> [ Clean Working Conditions ] Fuel System
- Switch ignition on. Fuel pump must run audibly for approx. 2 seconds.
- Switch off ignition.
If Fuel Pump (FP) does not start up:
- Remove nuts - 1 - on right side of fuel delivery unit cover. If necessary, remove backrest support - 2 - or mounting bracket: --> Body Interior 72 Removal and Installation
- Disconnect connector from Fuel Pump (FP) Control Module (J538) - 5 -.
- Switch ignition on.
- Check voltage supply between connector terminals - 3 - and - 4 - using low voltage tester. LED must light up.
- Switch off ignition.
LED does not light up:
- Locate and repair open circuit in wiring using wiring diagram..
LED lights up (voltage supply OK):
- Remove high pressure in fuel system --> [ Fuel System ] Fuel System.
CAUTION!
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
- Remove fuel supply line - 1 -, auxiliary heater fuel line - 2 -, fuel pump connector - 3 - and vent line - 4 -.
• Press in securing ring to disengage the fuel line.
- Open locking ring using wrench (T10202).
- Check whether electrical wires between flange and Fuel Pump (FP) are connected.
If no open circuits are found:
- Fuel Pump (FP) faulty, replace fuel delivery unit.
- --> Engine Mechanical Fuel Injection and Ignition 20 Removal and Installation
Fuel Pressure, Checking
Observe Safety Precautions: --> [ Safety Precautions ] Fuel System
Observe Clean Working Conditions: --> [ Clean Working Conditions ] Fuel System
- Remove high pressure in fuel system --> [ Fuel System ] Fuel System.
CAUTION!
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully loosening the union nut.
- Place a cloth around connection and loosen union nut - arrow - to reduce fuel pressure.
- Then tighten threaded connection again.
- Connect a Pressure Tester with Adapter , as shown.
- Make sure hose clamps are seated securely.
- Open shut-off valve of pressure gauge set. The lever points in the direction of flow.
- Remove nuts - 1 - on right side of fuel delivery unit cover. If necessary, remove backrest support - 2 - or mounting bracket: --> Body Interior 72 Removal and Installation
- Disconnect connector from Fuel Pump (FP) Control Module (J538) - 5 -.
- Disconnect harness connector - 3 - from flange of fuel delivery unit.
- Connect Hand held remote starter (jumper) with adapter cables from connector test kit to terminal - 1(+) - of Fuel Pump (FP) and to terminal - 3(+) - of harness connector of Fuel Pump (FP) Control Module (J538).
- Connect terminals - 4(-) - of harness connector and - 4(-) - of Fuel Pump (FP) using an adapter cable from connector test kit.
- Switch ignition on.
- Operate Hand held remote starter (jumper) () and observe display of pressure tester while doing this.
Fuel pressure must increase up to a maximum pressure of 6 bar.
• When releasing control button of remote control, fuel pressure decreases to approx. 5.6 bar.
If fuel pressure is OK, check retaining pressure --> [ Residual Pressure, Checking ].
If specification is exceeded:
- Pressure relief valve in sensor flange faulty, replace sensor flange.--> Engine Mechanical, Fuel Injection and Ignition 20 Removal and Installation
If specification is not obtained:
- Check fuel lines for possible restrictions (kinks) or blockages.
- Check all fuel lines in fuel tank for leaks.
- Check fuel filter for leaks.
If no malfunction can be found:
- Replace sensor flange with pressure relief valve.--> Engine Mechanical, Fuel Injection and Ignition 20 Removal and Installation
- Repeat test.
If fuel pressure is not obtained again:
- Fuel Pump (FP) faulty, replace fuel delivery unit.--> Engine Mechanical, Fuel Injection and Ignition 20 Removal and Installation
Residual Pressure, Checking
Test conditions
• The Pressure Gauge remains connected --> [ Fuel Pressure, Checking ]
• Fuel pressure of approx. 5.6 bar is displayed on pressure tester, checking --> [ Fuel Pressure, Checking ].
• Hand held remote starter (jumper) is connected.
Test sequence
- Watch pressure drop on gauge. After 10 minutes pressure must not drop below a 4.0 bar decrease.
If pressure drops below 4.0 bar:
- Operate Hand held remote starter (jumper) while doing this, observe display of pressure tester.
Fuel pressure must increase up to a maximum pressure of 6 bar.
- Release control button of Hand held remote starter (jumper) and immediately close shut-off valve of pressure tester. Then lever the points perpendicular to flow direction - arrow -.
• When releasing control button of Hand held remote starter (jumper), fuel pressure decreases to approx. 5.6 bar.
If pressure drops below 4.0 bar again:
(Leak on fuel tank side)
- Check connections to fuel tank for leaks.
If no malfunction can be found:
- Check fuel filter for leaks.
- Check fuel line to sensor flange for leaks.
- Check all additional fuel lines in fuel tank for leaks.
If no malfunctions are found on fuel line:
- Pressure relief valve in fuel delivery unit flange faulty.
- Replace sensor flange which contains the pressure relief valve.
Delivery Rate, Checking
- Remove high pressure in fuel system --> [ Fuel System ] Fuel System.
CAUTION!
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully loosening the union nut.
Test sequence
Observe Safety Precautions: --> [ Safety Precautions ] Fuel System
Observe Clean Working Conditions: --> [ Clean Working Conditions ] Fuel System
• A second technician is needed for the following task.
- Connect Pressure Gauge with adapter , as shown.
- However, do not connect ends of Hose to fuel rail connector.
- Hold end of Hose in a measuring container.
- Open shut-off valve of pressure gauge. The lever points in direction of flow.
- Switch ignition on.
- Operate Hand held remote starter (jumper). Slowly close shut-off tap, until pressure gauge shows 4 bar fuel pressure. From this point on do not move position of shut-off tap.
- Do not operate Hand held remote starter (jumper) any more.
- Empty measuring container.
- Operate remote control for 15 seconds.
- Compare quantity of fuel delivered with minimum delivery rate in diagram (cm3/15s).
• Voltage at fuel pump with engine stopped and pump running is approx. 2 volts less than battery voltage.
If minimum delivery rate is not attained:
- Check fuel lines for possible restrictions (kinks) or blockages.
If lines are OK:
- Replace fuel filter.
- Repeat test.
If specified value is again not obtained:
- Fuel Pump (FP) faulty, replace fuel delivery unit.
If delivery rate has been attained but nevertheless you suspect a fuel supply system malfunction (e.g. intermittent failure of fuel supply system):
- Check Fuel Pump (FP) current draw --> [ Delivery Rate, Checking ].
Delivery Rate, Checking
- Check current draw of fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Connect a multimeter with electrical current probe to wire of 4-pin connector terminal - 1 - - arrow - from wiring harness to Fuel Pump (FP) unit, right.
- Start engine and run at idle speed.
- Measure current draw of fuel pump. Specified value: max. 11 amps.
If current draw is exceeded:
- Fuel Pump (FP) faulty, replace fuel delivery unit.
• If malfunction in fuel system is sporadic, test can also be performed during a road test, but a second person is required.