Fuel Supply System Components
Fuel Pumps, Checking
Special tools, testers and auxiliary items required
- Wrench T10202
- Pressure gauge V.A.G 1318
- Adapter V.A.G 1318/7
- Adapter V.A.G 1318/9
- Hose V.A.G 1318/13
- Adapter For VAG1318 VAG1318/17
Special tools, testers and auxiliary items required
- Remote control connection V.A.G 1348/3A
- Multimeter V.A.G 1715
- Spring-type clip pliers VAS 5024A
- Diesel Extractor VAS 5226
- Not illustrated:
- Adapter V.A.G 1318/20
- Adapter V.A.G 1318/20-1
- Hose V.A.G 1318/24
- Adapter cable V.A.G 1348/3-3
- Measuring container
- Wiring diagram
Checking delivery rate
Test conditions
- Fuses - 13 - and - 14 - - arrows - must be removed from their sockets.
- Fuel pump relays - 1 - and - 2 - for left and right fuel delivery units must be removed from their sockets.
- Battery voltage at least 11.5 V
Test sequence
- Remove fuel filler cap from fuel filler tube.
- Connect remote control for VAG 1348 V.A.G 1348/3A with the adapter cable V.A.G 1348/3-3 to connection - arrow - for fuel pump relay for right fuel delivery unit.
- Connect positive clamp of - 1 - of remote control to positive terminal in engine compartment.
- Install adapter V.A.G 1318/20-1 on to adapter V.A.G 1318/20 .
- Turn valve (on T-piece) counter-clockwise until completely open.
CAUTION: Fuel supply lines are under pressure. Before opening fuel system, connect Diesel Extractor VAS 5226 and release pressure.
- Remove breather valve.
- Connect Adapter V.A.G 1318/20 with Adapter V.A.G 1318/20-1 and Diesel Extractor VAS 5226 to bleed valve - 1 - .
- Turn valve (on T-piece) clockwise into bleed valve to stop.
- When fuel pressure has been released, the fuel system may be opened.
Check delivery quantity of right pump
- Pull fuel supply hose - 1 - off fuel rail.
- Hold hose in measuring container - 2 - with capacity of at least 1000 cu.cm.
- Empty measuring container before making measurement.
- Operate remote control for 15 seconds: At least 3 fuel per 15 seconds must be delivered.
Check delivery quantity of left pump
- Connect remote control for VAG 1348 V.A.G 1348/3A with adapter cable V.A.G 1348/3- 3 to connection - arrow - for fuel pump relay for left fuel delivery unit.
- Empty measuring container before making measurement.
- Operate remote control for 15 seconds again. At least 3 fuel per 15 seconds must be delivered.
- Also test both fuel delivery units as follows:
- Connect Adapter V.A.G 1348/3-3 to fuel pump relay connections for left and right fuel delivery units.
- Operate remote control for 10 seconds: At least 800 cu.cm fuel per 10 seconds must be delivered.
If minimum delivery rate is not attained:
- Check fuel lines for possible restrictions (kinks) or blockages.
If lines are OK:
- Replace fuel filter:
If delivery rate has been attained but nevertheless you suspect a fuel supply system malfunction (e.g. intermittent failure of fuel supply system):
- Check current consumption of fuel pumps .
Current draw of pumps, checking
- Check current draw of each individual Fuel Pump (FP) as follows:
- Reconnect all disconnected fuel lines.
- Connect current clamp of multimeter V.A.G 1715 to wire of 4-pin connector contact - 1 - - arrow - from wiring harness to right fuel delivery unit.
- Start engine and run at idle speed.
- Measure current draw of fuel pump. Specified value: max. 11 amps.
If current draw is exceeded:
CAUTION: Fuel supply lines are under pressure. Before opening fuel system, connect Diesel Extractor VAS 5226 and release pressure.
- Right fuel pump is faulty. Replace fuel delivery unit.
- Repeat test on left fuel delivery unit.
If current draw is exceeded:
- Left Fuel Pump (FP) malfunctioning, replace fuel pump unit.
NOTE: If malfunction in fuel system is sporadic, test can also be performed during a road test, but a second person is required.
Check valves of Fuel Pumps (FP), checking Conditions
- Remote control for VAG 1348 V.A.G 1348/3A is still connected.
NOTE: With this check, the fuel supply line connections from the fuel delivery units to the point at which pressure gauge V.A.G 1318 is connected will be checked for leaks at the same time.
Test sequence
- Turn valve on T-piece of adapter V.A.G 1318/20 counter-clockwise until completely open.
- Connect pressure tester V.A.G 1318 to breather valve - 1 - as shown using adapter V.A.G 1318/20 , V.A.G 1318/20-1 , V.A.G 1318/9 and Diesel Extractor VAS 5226 .
- Install valve on T-piece of adapters V.A.G 1318/20 clockwise into bleed valve to stop.
- Open cut-off tap of pressure tester and operate remote control briefly to bleed air.
- Then, close pressure gauge shut-off tap - arrow - (lever perpendicular to direction of flow).
- Operate remote control at short intervals, until a pressure of approx. 4 bar has built up.
CAUTION: Danger of spray when opening the shut-off tap Diesel Extractor VAS 5226 must be connected.
- If pressure builds up too high, lower excess pressure by carefully opening shut-off tap.
- Watch pressure drop on gauge. After 10 minutes pressure must not drop below a 3.0 bar decrease.
If pressure drops:
- Check fuel lines and connections to fuel tank for leaks.
If no fault is detected in the wiring:
CAUTION: Fuel supply lines are under pressure. Before opening fuel system, connect Diesel Extractor VAS 5226 and release pressure.
- In addition, wrap a cloth around connection to catch fuel which runs out.
- Remove pressure gauge V.A.G 1318 with adapters .
Check right pump check valve
Test conditions
- Fuel pump relays - 1 - and - 2 - for left and right fuel delivery units must be removed from their sockets.
Test sequence
- Disconnect 4 pin connector from left flange
- Remove locking ring from left sensor flange (fuel filter) using fuel tank sensor Wrench T10202 .
- Carefully pry up sensor flange and raise it slightly.
- Disconnect connector next to fuel filter for attaching pressure tester V.A.G 1318 .
- Pull fuel supply hose - 2 - from right fuel delivery unit off fuel filter - 1 - .
- Let fuel from connecting piece - 1 - flow back into tank.
- Close pressure gauge shut-off tap - arrow - (lever perpendicular to direction of flow).
- Connect pressure tester V.A.G 1318 with adapter V.A.G 1318/7 , hose adapter V.A.G 1318/13 and Adapter For VAG1318 V.A.G 1318/17 as shown.
NOTE: Ensure that fuel supply line connection engages audibly when joined.
- Attach connectors to filter housing and flange again.
- Connect remote control for VAG 1348 V.A.G 1348/3A with adapter cable V.A.G 1348/3- 3 to connection - arrow - for fuel pump relay for right fuel delivery unit.
- Operate remote control at short intervals, until a pressure of approx. 4 bar has built up.
- Watch pressure drop on gauge. After 10 minutes the pressure must not drop below a 3.0 bar decrease.
If pressure drops:
- Right fuel pump is faulty. Replace fuel delivery unit.
To change pressure tester set-up for left fuel pump:
- Open lever of pressure tester and let fuel flow back to fuel tank through hose V.A.G 1318/13 .
Check left pump check valve
- Pull fuel supply hose - 2 - from left fuel delivery unit off fuel filter - 1 - .
- If necessary, disconnect connectors from flange and filter housing and then attach pressure tester V.A.G 1318 .
- Close pressure gauge shut-off tap - arrow - (lever perpendicular to direction of flow).
- Connect pressure tester V.A.G 1318 with adapter V.A.G 1318/7 , hose adapter V.A.G 1318/13 and adapter V.A.G 1318/24 as shown.
NOTE: Ensure that fuel supply line connection engages audibly when joined.
- Connect remote control for VAG 1348 V.A.G 1348/3A with adapter cable V.A.G 1348/3- 3 to connection - arrow - for fuel pump relay for left fuel delivery unit.
- Operate remote control at short intervals, until a pressure of approx. 4 bar has built up.
- Watch pressure drop on gauge. After 10 minutes pressure must not drop below a 3.0 bar decrease.
If pressure drops:
- Left fuel pump is faulty. Replace left fuel delivery unit.
- Open lever of pressure tester and let fuel flow back to fuel tank through hose V.A.G 1318/13 .
- Remove pressure gauge V.A.G 1318 with adapters .