Checking fuel pressure of supplementary fuel pump V393 — VW

Checking fuel pressure of
supplementary fuel pump
V393
Special tools and workshop equipment required
Pressure gauge
VAS 6551
Adapter set
VAS 6551/5
Removal wedge
3409
Hose clip pliers
V.A.G 1921
Vehicle diagnosis and service information system
Fuel hose, commercially available
7,5 mm x 3 mm
WARNING
Bear in mind that the fuel pump can be activated due to opening of a door with the battery connected. Fuel can escape if the system has been opened.
Test prerequisites
Connect battery charger, battery voltage at least 12.5 volts
Electrical system
Rep. gr.
27
Battery; Charging battery
.
Fuses OK.
Current flow diagrams, Electrical fault finding and Fitting locations
.
Event memory OK
Vehicle diagnostic tester
.
Fuel filter OK.
Ensure that vehicle is placed on a level surface.
Fuel tank at least
1
/
2
full.
All electrical consumers, e.g. lights and rear window heating, must be switched off.
Note
The vehicle must be fuelled with the diesel fuel appropriate for the time of the year. Summer diesel fuel may coagulate (flock) at low winter temperatures.
Diesel fuel sold in the summer is guaranteed to be capable of filtration down to 0°C.
Diesel fuel sold in the summer/winter transition is guaranteed to be capable of filtration down to -10°C.
Diesel fuel sold in the winter is guaranteed to be capable of filtration down to -20°C.
Test sample, if unsure in winter.
Expose sample to low ambient temperature for approx. 1 hour.
If the fuel coagulates (flocks) at temperatures down to -20°C, it is unsuitable for low temperatures. This coagulation may block the strainer in the fuel delivery unit as well as the fuel filter.
Test procedure
Observe safety precautions
Chapter
.
Observe rules for cleanliness
Chapter
.
Switch off ignition.
Remove engine cover panel
Rep. gr.
10
Engine cover; Removing and installing engine cover panel
.
Remove intake hose and air filter upper part
Rep. gr.
23
Diesel direct injection system; Assembly overview - air filter
.
Detach clip
arrow
and pull fuel supply line
2
off
supplementary fuel pump
V393
1
.
WARNING
The fuel line is under pressure.
Risk of injury to eyes and skin from fuel.
Wear eye protection and protective clothing to avoid eye injuries and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully opening the connection point.
Fit
hose
VAS 6551/1
into fuel supply line
2
and secure it with clip.
Connect
hose
VAS 6551/1
to connection
B
of
pressure tester (diesel)
VAS 6551
.
Connect standard hose
3
to connection
A
of
pressure tester (diesel)
VAS 6551
and secure it with clip.
Connect standard hose to connection of
supplementary fuel pump
V393
1
and secure it with a clip.
Switch on
pressure tester
VAS 6551
by pressing
On/Off
button.
Open shut-off taps
A
and
B
of
pressure tester (diesel)
VAS 6551
1
.
Close shut-off valve
C
.
Connect
vehicle diagnostic tester
.
Select
Guided Functions
.
Select function
Bleed fuel system
.
Follow instructions on
vehicle diagnostic tester
.
Note
The fuel pump will now be activated.
Read off fuel pressure on
pressure gauge
VAS 6551
.
Specification is min. 4.0 bar.
Exit function by pressing button
►
.
If the specification is not attained:
Check fuel lines in engine compartment for possible restrictions (kinks), blockages and damages.
Check fuel lines in engine compartment for leaks.
If no fault is found:
Check fuel pressure of fuel pumps
V276
/
V277
Chapter
.
If specification is attained for fuel pumps
V276
/
V277
:
Renew
supplementary fuel pump
V393
Chapter
.