Engine Mechanical, Fuel Injection Ignition - MFI

Fuel Pump, Checking

Special tools, testers and auxiliary items required
- Pressure gauge V.A.G 1318
- Adapter V. A. G 1318/6
- Adapter V.A.G 1318/11
- Hose adapter V.A.G 1318/16
- Adapter V.A.G 1318/17
- Double connection V.A.G 1318/23

Special tools, testers and auxiliary items required
- Wrench T10202
- Remote control connection V.A.G 1348/3A
- Connector test set V.A.G 1594C
- Multimeter V.A.G 1715
- Torque wrench V.A.G 1332
- Measuring container

Function and voltage supply, checking
Read safety precautions before beginning work.

Test conditions
- Battery voltage at least 11.5 V.
- Fuse for Fuel Pump (FP) OK.
- Fuel Pump (FP) Control Module J538 OK.
- Low Fuel Pressure Sensor G410 OK.

Test sequence

NOTE: Fuel Pump (FP) function is checked via output Diagnostic Test Mode (DTM).

- Connect vehicle diagnosis, testing and information system VAS 5051 A as follows:
- Connect diagnostic cable connector to Data Link Connector (DLC) in drivers footwell.
- Switch ignition on.
- Press buttons for "Vehicle Self-Diagnosis", "01 - Engine electronics" and "03 - Output Diagnostic Test Mode (DTM)" on display in succession.
- Press right arrow button on display until output Diagnostic Test Mode (DTM) of Fuel Pump (FP) electronics.

Fuel Pump (FP) must now accelerate slowly up to maximum RPM.

NOTE: Fuel Pump (FP) runs quietly.

- Switch off ignition.

If Fuel Pump (FP) does not start up:
- Remove seat bench.

- Disconnect connector from Fuel Pump (FP) Control Module J538

- Check voltage supply between terminals - 1 - and - 6 - using voltage tester V.A.G 1527B. LED must light up.

LED does not light up:
- Locate and repair open circuit in wiring using wiring diagram.

LED lights up (voltage supply OK):

- Remove cover - 1 - with Fuel Pump (FP) Control Module J538 - 2 - from fuel delivery unit.

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 connection. Then release pressure by carefully pulling hose off connection.

- Disconnect harness connector - A - and fuel line - B - from flange.

NOTE: Press in securing ring to disengage 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.

Fuel pressure, checking

Test sequence
Read safety precautions before beginning work.
- Observe 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 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.
- Remove fuel supply hose completely and catch escaping fuel using a rag.

- Install pressure gauge V.A.G 1318 with adapter V.A.G 1318/6 and adapter set V.A.G 1318/17 in place of fuel supply hose.
- Open shut-off valve of pressure gauge set. Lever will then point in position - A -.
- Remove seat bench.

- Disconnect harness connector from Fuel Pump (FP) Control Module J538 - 2 - and remove cover - 1 - together with Fuel Pump (FP) Control Module J538.

- Disconnect harness connector - A - from flange of fuel delivery unit.

- Connect remote control V.A.G 1348/3A with adapter cables from connector test kit V.A.G 1594C to terminal -1(+) - of Fuel Pump (FP) and to terminal -1(+) - of harness connector of Fuel Pump (FP) Control Module J538.
- Connect terminals - 6(-) - of harness connector and - 5(-) - of Fuel Pump (FP) using an adapter cable from connector test kit V.A.G 1594C.
- Operate remote control V.A.G 1348/3A and observe display of pressure tester V.A.G 1318 while doing this.

Fuel pressure must increase up to a maximum pressure of 6 bar.

NOTE: When releasing control button of remote control V.A.G 1348/3A, fuel pressure decreases to approx. 5.6 bar.

If fuel pressure is OK, check retaining pressure.

If specification is exceeded:
- Pressure relief valve in flange faulty, replace flange with fuel filter on vehicles with all wheel drive or on vehicles with front wheel drive.

If specification is not obtained:
- Check fuel lines for possible restrictions (kinks) or blockages.

If no malfunction can be found:
- Replace flange with fuel filter and pressure relief valve.
- Repeat test.

If fuel pressure is not obtained again:
- Fuel Pump (FP) faulty, replace fuel delivery unit

Residual pressure, checking

Test conditions
- Pressure tester V.A.G 1318 connected.
- Fuel pressure of approx. 5.6 bar is displayed on pressure tester V.A.G 1318, checking.
- Remote control connection V.A.G 1348/3A 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 further:
- Operate remote control V.A.G 1348/3A and observe display of pressure tester V.A.G 1318 while doing this.

Fuel pressure must increase up to a maximum pressure of 6 bar.

- Release control button of remote control V.A.G 1348/3A and immediately close shut-off valve of pressure tester. Lever will then point in position - B -.

NOTE: When releasing control button of remote control V.A.G 1348/3A, fuel pressure decreases to approx. 5.6 bar.

If pressure drops again:
(Leak on engine side)
- Check connections to fuel rails and high pressure pump for leaks, Fuel rail with high pressure pump and fuel injectors, assembly overview.

If no malfunction can be found:
- Replace high pressure pump, intake manifold.

If pressure no longer drops now:
(Leak on fuel tank side)
- Check fuel line to flange for leaks.

If no malfunctions are found on fuel line:
- Check valve in flange with fuel filter faulty, replace flange with fuel filter on vehicles with front wheel drive: on vehicles with all wheel drive.

Delivery rate, checking

Test sequence
- Remove seat bench.

- Disconnect harness connector from Fuel Pump (FP) Control Module J538 - 2 - and remove cover - 1 - together with Fuel Pump (FP) Control Module J538.

- Disconnect harness connector - A - from flange of fuel delivery unit.

- Disconnect supply line - arrow - and catch escaping fuel using a rag.

NOTE: Press in securing ring to disengage the fuel lines.

- Connect pressure gauge V.A.G 1318 with double connection V.A.G 1318/23 and adapter set V.A.G 1318/17 to fuel supply line.
- Connect hose adapter V.A.G 1318/16 to adapter V.A.G 1318/11 of pressure gauge and hold it in a measuring container.

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 -.
- Operate remote control V.A.G 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.
- Delivery rate of Fuel Pump (FP) is dependent on battery voltage. Therefore, also connect multimeter V.A.G 1715 to Fuel Pump (FP) using adapter cables from connector test kit V.A.G 1594C.
- Operate remote control for 30 seconds and simultaneously measure voltage at Fuel Pump (FP).

- Compare quantity of fuel delivered with specification.

*) Minimum delivery rate cu.cm /30 s
**) Voltage at Fuel Pump (FP) with engine at stand still and pump running.

Example:
During test, a voltage of 10.5 Volts is measured. This results in a minimum delivery rate of approx. 580 cu.cm/30 s.

If specification is not obtained:
- Check fuel line for possible restrictions (kinks) or clogging.

If no malfunction can be found:
- Remove fuel delivery unit and check filter strainer for dirt.
- If there is no malfunction here as well, replace flange with 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.

Current draw, checking

Test sequence
- Remove seat bench.

- Remove cover - 1 - with Fuel Pump (FP) Control Module J538 - 2 - from fuel delivery unit.

- Connect multimeter V.A.G 1715 with current pick-up on to cable to 5-pin connector terminal 1 - arrow-.
- Start engine and run at idle speed.
- Measure current draw of fuel pump. Specified value: max. 9 amps.

NOTE: If malfunction in fuel system is sporadic, test can also be performed during a road test, but a second person is required.

If current draw is exceeded:
- Fuel Pump (FP) faulty, replace fuel delivery unit.