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Fuel system pressure regulator and residual pressure: checking > < Operation and voltage supply: checking

Leon Mk2

Fuel flow: checking
Fuel flow: checking
Test requirements
l  Voltage supply for the fuel pump, OK → Chapter.
l  V.A.G 1348 remote control -V.A.G 1348/3A- connected
l  Fuel pressure regulator and retention pressure, correct → Chapter
l  The fuel delivery rate is measured at 3 bar, therefore, before measuring the delivery rate it is necessary to check the fuel system pressure and the retaining pressure → Chapter.
Test sequence
  Note
The delivery rate of the fuel pump is measured at 3 bar. Therefore, check fuel pressure before measuring delivery rate.
–  Remove cover from fuse holder.
   
–  Connect the remote control -VAG 1348/3A- with adaptor cable -SAT 1348/3-3- to the right hand side contact to fuel pump and battery positive (+).
  N20-0513
–  Detach fuel return pipe -1-, pressing in the coupling keys for fuel pipes.
  WARNING
Fuel system is under pressure! Wear safety gloves and glasses to avoid injury and contact with skin. Before opening the system place a cloth around the connection. Then release pressure by carefully pulling fuel hose from connection.
–  Connect adapter -VAG 1318/17- to pressure tester and place adapter end in a measuring container.
–  Operate the remote control -VAG 1348/3A- for 5 seconds, to fill the fuel filter.
–  Empty measuring container.
–  The quantity of fuel delivered by the fuel pump is dependent upon battery voltage. Therefore the multimeter -VAG 1715- should be connected to the two outer pins on the fuel pump, using themeasuring tool set -VAG 1594C- (the pump switch remains connected).
–  Operate the remote control -VAG 1348/3A- for 30 seconds, and measure fuel pump voltage.
  N20-0526
–  Compare the quantity of fuel delivered with specification.
1)  Minimum delivery cm3/30 s
2)  Voltage on the fuel pump with the engine stopped and the pump operating (about 2 volts less than the battery voltage).
Readout example:
During the test, the fuel pump is measured at 10.5 volts. With this voltage the pump should produce a minimum delivery rate of 540 c.c./30 s.
If the minimum delivery rate is not attained:
–  Check the fuel pipes to the filter for possible restrictions (kinks) or blockages.
If fuel pipes are OK:
–  Check delivery range before filter.
  WARNING
Fuel system is under pressure! Wear safety gloves and glasses to avoid injury and contact with skin. Before opening the system place a cloth around the connection. Then release pressure by carefully pulling fuel hose from connection.
  N20-0134
–  Pull supply hose -1- off inlet to fuel filter, press buttons on hose couplings to do this.
–  Connect fuel supply pipe to pressure tester -VAG 1318-, using adapter -VAG 1318/17-
–  Connect adaptor -VAG 1318/11- and -VAG 1318/1- to pressure tester and place adaptor end in a measuring container.
–  Open cut-off tap on pressure gauge -VAG 1318-. The lever then points in the throughflow direction -A-.
–  Operate remote control -VAG 1348/3A-, and slowly close shut-off tap, until pressure gauge -VAG 1318- shows approx. 3 bar. From this point on do not move position of cut-off tap.
–  Empty measuring container.
–  The quantity of fuel delivered by the fuel pump is dependent upon battery voltage. Therefore the multimeter -VAG 1715- should be connected to the two outer pins on the fuel pump, using themeasuring tool set -VAG 1594C- (the pump switch remains connected).
–  Operate the remote control -VAG 1348/3A- for 30 seconds and measure fuel pump voltage.
–  Repeat delivery rate check → Anchor.
If the minimum delivery rate is now attained:
–  Replace fuel filter.
If the minimum delivery rate is again not attained:
–  Remove the fuel delivery unit and check the strainer filter for soiling → Chapter.
Only when up to now no fault has been detected:
–  Replace fuel delivery unit → Chapter.
If the delivery rate has been attained but nevertheless you suspect a fuel supply system fault (e.g. intermittent failure of fuel supply system):
–  Check the current draw of the fuel pump as follows:
–  Reconnect all disconnected fuel pipes.
  N20-0531
–  Using the current pincers, connect the Multimeter -VAG 1715- to one of the supply cables of the fuel pump (exterior contacts of the flange connector).
–  Start engine and run at idling speed.
–  Measure the current consumption of the fuel pump.
t  Specification: 8 amps maximum
  Note
If there is a temporary fuel system fault, the check can also be carried out during a test drive, with the help of a second person.
If the current draw is exceeded:
–  Replace fuel delivery unit → Chapter.
  N20-0402

Fuel system pressure regulator and residual pressure: checking > < Operation and voltage supply: checking