Delivery Quantity of Pumps, Checking

Delivery Quantity Of Pumps, Checking

Checking delivery quantity of right pump
Checking delivery quantity of left pump

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.

Check delivery quantity of right pump







- 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 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 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 cu.cm 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.

Current draw of pumps, checking
- 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.

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