Fuel Pump Checking, with One Piece Intake Manifold
Fuel Pump Checking, with One Piece Intake Manifold
--> [ Function and Voltage Supply, Checking ]
--> [ Fuel Pressure, Checking ]
--> [ Residual Pressure, Checking ]
--> [ Delivery Quantity, Checking ]
--> [ Current Draw, Checking ]
Special tools, testers and auxiliary items required
• Wrench (T10202)
• Pressure gauge (VAG 1318)
• Adapter (VAG 1318/6) and adapter (VAG 1318/7)
• Adapter (VAG 1318/12)
• Remote control connection (VAG 1348/3A)
• Multi meter (VAG 1715)
• Torque wrench (VAG 1332)
• Connector test set (VAG 1594C)
• Voltage tester (VAG 1527B)
• Measuring container
• Wiring diagram
Function and Voltage Supply, Checking
Test Conditions
• Battery voltage at least 11.5 V
• Fuse for Fuel Pump (FP) OK.
• FP control module (J538) OK.
• Low fuel pressure sensor (G410) OK.
Test Sequence
- Read safety precautions before beginning work.
- Observe the rules for cleanliness.
- Connect the tester.
- Switch on ignition.
- Press the following buttons in the tester screen one after another.
Vehicle Self-Diagnosis
On Board Diagnosis (OBD) >
01 - Engine Electronics >
Output diagnostic Test Mode >
- Press right arrow button on display until output Diagnostic Test Mode (DTM) of FP electronics.
FP must now accelerate slowly up to maximum RPM.
- Switch off ignition.
If FP Does Not Start Up
- Fold rear seat bench forward. On vehicles from 12.06, rear seat bench must be removed.
- Cut open carpet on right side from point - A - to point - B - in pre-cut area - arrow -.
- Remove the nuts - 1 - on the right side of the fuel delivery unit cover. If necessary, remove backrest support - 2 - or mounting bracket.
- Disconnect connector from FP control module (J538) - 5 -.
- Switch ignition on.
- Check voltage supply between connector terminals - 3 - and - 4 - using voltage tester (VAG 1527B). Light Emitting Diode (LED) must light up.
- Switch off ignition.
LED Does Not Light Up
- Locate and repair open circuit in wiring using wiring diagram, refer to.
LED Lights Up (Voltage Supply OK)
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 disconnecting hose 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 FP are connected.
If no open circuits are found:
- FP faulty, replace fuel delivery unit.
Fuel Pressure, Checking
• Output Diagnostic Test Mode (DTM) activates the fuel pump.
- Read safety precautions before beginning work.
- Observe the rules for cleanliness.
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.
- Lay a cloth around threaded connection and loosen union nut - arrow - from fuel supply hose. To do so, counter hold on fuel supply line using a wrench.
- Install pressure gauge (VAG 1318) with adapter (VAG 1318/6) and adapter (VAG 1318/7) as shown.
- Open shut-off valve of pressure gauge set. Lever will then point in position - A -.
- Connect the tester.
- Switch on ignition.
- Press the following buttons in the tester screen one after another.
Vehicle Self-Diagnosis
On Board Diagnosis (OBD) >
01 - Engine Electronics >
Output diagnostic Test Mode >
- Press right arrow button on display until output Diagnostic Test Mode (DTM) of Fuel Pump (FP) electronics.
FP must now accelerate slowly up to maximum RPM.
Fuel pressure must increase up to a maximum pressure of 6 bar.
If fuel pressure is OK, check retaining pressure.
• The fuel pressure decreases to about 5.6 bar after output diagnostic test mode.
If the Specification is Exceeded
- Pressure relief valve in sensor flange faulty, replace sensor flange --> [ (Item 15) Flange ] .
If the Specification is Not Obtained
- Check the 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 --> [ (Item 15) Flange ] .
- Repeat the test.
If fuel pressure is not obtained again:
- FP faulty, replace fuel delivery unit.
Residual Pressure, Checking
Test Conditions
• Pressure tester (VAG 1318) connected.
• Fuel pressure of approximately 5.6 bar is displayed on pressure tester (VAG 1318), checking. Refer to --> [ Fuel Pressure, Checking ].
Test Sequence
- Watch pressure drop on gauge. After 10 minutes the pressure must not drop below a 4.0 bar decrease.
If the pressure drops further:
- Repeat fuel pump electronics output diagnostic test mode. Fuel pressure must increase up to a maximum pressure of 6 bar.
- Immediately close the pressure gauge shut-off valve - arrow -. Lever will then point in position - B -.
• The fuel pressure decreases to about 5.6 bar after output diagnostic test mode.
If the Pressure Drops Again
(Leak on engine side)
- Check connections to fuel rail and high pressure pump for leaks.
If no malfunction can be found:
- Replace high pressure pump.
If Pressure No Longer Drops Now:
(Leak on fuel tank side)
- Check fuel filter for leaks.
- Check fuel line to sensor flange --> [ (Item 15) 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 with pressure relief valve --> [ (Item 15) Flange ] .
Delivery Quantity, Checking
Test Sequence
- Read safety precautions before beginning work.
- Observe the rules for cleanliness.
- Fold rear seat bench forward. On vehicles from 12.06, rear seat bench must be removed.
- Cut open carpet on right side from point - A - to point - B - in pre-cut area - arrow -.
- Remove the nuts - 1 - on the right side of the fuel delivery unit cover. If necessary, remove backrest support - 2 - or mounting bracket.
- Disconnect connector from Fuel Pump (FP) control module (J538) - 5 -.
- Disconnect harness connector - 3 - from flange of fuel delivery unit.
- Connect remote control (VAG 1348/3A) with adapter cables from connector test kit (VAG 1594C) to terminal - 1 (+) - of FP and to terminal - 3 (+) - of harness connector of FP control module (J538).
- Connect terminals - 4 (-) - of harness connector and - 4 (-) - of FP using an adapter cable from connector test kit (VAG 1594C).
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.
- Lay a cloth around threaded connection and loosen union nut - arrow - from fuel supply hose. To do so, counter hold on fuel supply line using a wrench.
- Install pressure gauge (VAG 1318) with adapter (VAG 1318/6), adapter (VAG 1318/7) and adapter (VAG 1318/12) as shown.
CAUTION!
Danger of spraying when opening shut-off valve; wear protective goggles and protective clothing to prevent injuries and contact with skin. Hold container in front of free connection of pressure measuring device.
- Open shut-off valve of pressure gauge set. Lever will point in direction of flow - A -.
- Switch ignition on.
• A second mechanic is needed for the following task.
- Hold adapter (VAG 1318/6) over a measuring container.
- Operate remote control (VAG 1348/3A). Slowly close shut-off tap, until pressure gauge shows 4 bar. From this point on do not move position of shut-off tap.
- Empty measuring container.
- Operate remote control for 15 seconds: At least 350 cm3 fuel per 15 seconds must be delivered.
If the minimum delivery rate is not attained:
- Check the fuel lines for possible restrictions (kinks) or blockages.
If lines are OK:
- Replace fuel filter.
- Repeat the test.
If specified value is again not obtained:
- FP faulty, replace fuel delivery unit.
If the delivery rate has been attained but nevertheless you suspect a fuel supply system malfunction (e.g. intermittent failure of fuel supply system):
- Check FP current draw. Refer to --> [ Current Draw, Checking ].
Current Draw, Checking
- Check the current draw of the fuel pump as follows:
- Reconnect all disconnected fuel lines.
- Connect multi meter (VAG 1715) with electrical current probe to wire of 4 pin connector terminal - 1 - - arrow - from wiring harness to Fuel Pump (FP) unit, right.
- Start the engine and run at idle speed.
- Measure current draw of fuel pump. Specified value: max. 11 amps.
If the current draw is exceeded:
- 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.