Fuel Pumps, Checking Delivery Quantity
Fuel Pumps, Checking Delivery Quantity
Special tools, testers and auxiliary items required
• Diesel extractor (VAS 5226)
• Pressure gauge (V.A.G 1318)
• Adapter (V.A.G 1318/9)
• Adapter (V.A.G 1318/10)
• Adapter (V.A.G 1318/24)
• Remote control connection (V.A.G 1348/3 A)
• Multimeter (V.A.G 1715)
• Spring-type clip pliers (VAS 5024 A)
• Wiring diagram
• Measuring container
Test conditions
• Fuses - 13 - and - 14 - - arrows - must be removed from their sockets.
• Battery voltage at least 11.5 V
• Fuel pump relays - 1 - and - 2 - for left and right fuel delivery units must be removed from their sockets.
Test sequence
- Read safety precautions before beginning work.
- Remove fuel filler cap from fuel filler tube.
- First, relieve fuel pressure as follows:
CAUTION!
Fuel supply lines are under pressure! Wear protective goggles and protective gloves to avoid damage and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
- Place a rag around connection to catch escaping fuel, and loosen fuel supply line - arrow -.
When fuel pressure has been released:
- Tighten threaded connection again.
Right Fuel Pump, Checking Delivery Quantity
- Connect remote control (V.A.G 1348/3 A) with adapter cable (V.A.G 1348/3-3) to connection - arrow - for fuel pump relay for right fuel delivery unit.
- Connect positive clamp of remote control to positive terminal in engine compartment.
- Pull fuel supply hose - 1 - off from fuel rail.
- Hold hose in measuring container - 2 - with capacity of at least 1000 cm3.
- Empty measuring container before making measurement.
- Operate remote control for 15 seconds: At least 3 fuel per 15 seconds must be delivered.
Left Fuel Pump, Checking Delivery Quantity
- Connect remote control (V.A.G 1348/3 A) 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 connection for left and right fuel delivery units.
- Empty measuring container before making measurement.
- Operate remote control for 10 seconds: At least 800 cm 3 fuel per 10 seconds must be delivered.
If minimum supply quantity is not achieved during one of the tests:
- 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.
Fuel Pumps, Checking Current Draw
- Check current draw of each individual Fuel Pump (FP) as follows:
- Reconnect all disconnected fuel lines.
- Cut open carpet from point - A - to point - B - in pre-cut area - arrows -.
- Remove nuts - 1 - from cover. If necessary, unbolt backrest support - 2 - or support mounting.
- Connect current clamp of multimeter (V.A.G 1715) to the wire of the 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:
- Right fuel pump is faulty. Replace fuel delivery unit.
- Repeat test on left fuel delivery unit.
If current draw is exceeded:
CAUTION!
Fuel supply lines are under pressure! Wear protective goggles and protective gloves to avoid damage and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
- Left fuel pump is 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.