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