Volkswagen Golf / Golf GTI / Jetta. Manual — part 78

20-35

Note:

If the fuel system malfunction is
intermittent, perform the check
during a test drive with the
assistance of a 2nd person.

If the current draw is exceeded:

Checking fuel pump non-return
valve

Test conditions

- Connect multimeter VAG 1715 to

wire (arrow) for contact 1of 4-pin
connector using current pick-up
clamp.

- Start engine and run at idling

speed.

- Measure current draw of fuel

pump.

Specification: max. 8 amps.

- Fuel pump faulty, replace fuel

delivery unit

Page 20-15

,

Removing and installing fuel
delivery unit.

Remote control VAG 1348/3A is

still connected.

Pressure gauge VAG 1318 is

still connected.

Components of fuel supply system, servicing

20-36

Test sequence

Note:

With this check the fuel supply line
connections from the fuel delivery
unit to the point at which the
pressure gauge VAG 1318 is
connected will be checked for leaks
at the same time.

WARNING!

Danger of spray when opening the
shut-off-tap; hold container in
front of the free connection on the
pressure gauge.

If the pressure drops further:

- Close pressure gauge shut-off tap

(lever across flow direction -
position B-).

- Operate remote control at short

intervals, until a pressure of
approx. 3 bar has built up.

- If pressure builds up too high,

lower excess pressure by
carefully opening shut-off tap.

- Observe pressure drop on gauge.

Over a duration of 10 minutes
pressure must not drop below a
2.5 bar decrease.

Components of fuel supply system, servicing

20-37

- Check pipe connections for leaks.

If no wiring fault is detected:

- Fuel pump faulty, replace fuel delivery unit

Page 20-15

, Removing and installing fuel

delivery unit.

Components of fuel supply system, servicing

20-38

Evaporative Emissions
(EVAP) system

Function

Depending on air pressure and ambient

temperature, fuel vapor will form above the
level of fuel in the tank.

The EVAP system prevents these HC

emissions from escaping into the
atmosphere.

In limited quantities, fuel vapors located at

the highest point in the tank pass through a
gravity valve (which closes at an angle of 45

) and through a pressure retention valve

into the EVAP canister.

The activated charcoal in the canister stores

these vapors like a sponge.

When the Oxygen sensor control is active

when driving (engine warm), the EVAP
canister purge regulator valve -N80-
(sometimes called regeneration valve), is
activated (pulsed) from the engine control
module depending upon load and engine
speed. The opening period is dependent on
the input signals.

Intake manifold vacuum draws fresh air

through the vent opening on the underside of
the EVAP canister during the purging
procedure (regenerating the activated
charcoal). The fuel vapors stored in the
activated charcoal and fresh air are fed for
combustion in dosed quantities.

Evaporative Emissions (EVAP) system