Fuel Pressure: Testing and Inspection
WM 200201 Checking fuel pressure in the low-pressure system
Tools
Technical values
Preliminary work
Information
- The battery voltage must not fall below 12 volts during the fuel pressure check.
- Connect a suitable battery charger.
Information
- The battery voltage must not fall below 12 volts during the fuel pressure check.
- Connect a suitable battery charger.
1. Check the battery charge state using a voltmeter or the Porsche PIWIS Tester for example.
1.1. Connect a charger for the test.
WARNING
Highly inflammable or explosive materials
- Danger of fire or explosion
-> Avoid contact with hot parts or sources of ignition.
-> Use suction to remove ignitable vapours.
-> Attach warning sign in a clearly visible position.
2. Attach or mount a warning sign in a clearly visible position on the vehicle.
Example of a warning sign
3. Remove underbody panelling.
-> 519419 Removing and installing cover for rear underbody.
-> 519319 Removing and installing cover for centre underbody.
Checking fuel pressure
Checking fuel pressure - engine stopped
WARNING
Risk of damage to skin and eyes from toxic and caustic effects of fuel.
-> In case of contact with skin or eyes wash immediately with plenty of warm water and acid-free soap.
-> Consult a doctor as soon as possible.
-> Wear personal protective gear when working with fuel.
WARNING
Highly inflammable or explosive materials
- Danger of fire or explosion
-> Avoid contact with hot parts or sources of ignition.
-> Use suction to remove ignitable vapours.
-> Attach warning sign in a clearly visible position.
Tools:
Tool overview
Alternative tool (can only be used when the engine is stopped):
Pressure gauge 378a with connection line no. 17 from V.A.G. 1318
1. PIWIS Tester 9718 must be connected to the adapter line at the input socket in the passenger compartment and ignition must be switched on.
1.1. Switch on the Tester and select the relevant vehicle.
PIWIS Tester start page
2. Run the individual control unit search for DME.
2.1. To do this, select DME and press F12>>.
Control unit search
3. After running the individual control unit search for DME, select Special functions.
Special functions menu item
3.1. Select the menu item Drain tank.
Drain tank function
4. Open the retaining clip for the fuel lines -1- on the underbody and unclip the supply line.
4.1. To do this, open the clip -arrow- using a small screwdriver.
Opening retaining clip on fuel lines
5. Open the rapid-action coupling on the fuel pressure line -1-.
5.1. Wrap a cloth around the connection point (to prevent splashes), press the two locking lugs and pull the line apart.
Alternatively, relieve the fuel pressure. To do this, remove the fuse for the fuel pump, start the engine and leave it running until it stops.
Plug-in coupling on fuel pressure line
6. Connect special tool test pressure gauge with lines from K-Jetronic Tester V.A.G. 1318 WE 1291 to the fuel lines.
6.1. Engage pressure gauge on the transmission bracket using the chain.
6.2. Insert connection lines into the relevant couplings.
Test pressure gauge with connection lines (V.A.G. 1318) on the vehicle
6.3. Alternatively, the test can be performed using the pressure gauge 378a.
To do this, connect line no. 17 to the plug-in coupling for the fuel tank.
Test pressure gauge 378a
7. Activate the Drain tank (= activate fuel pump) function on the PIWIS Tester 9718 by pressing F8 Start.
Starting the Drain tank function
8. Read off the pressure shown on the pressure gauge.
=> Fuel pressure - engine not running: 5.0 bar+/-0.3 bar
9. Deactivate the Drain tank function by pressing F8 Stop.
9.1. Then, press F11 << a number of times to return to the start screen and switch off the Tester.
Deactivating the Drain tank function
10. Holding pressure test:
=> Pressure: 4.0 bar
11. Disconnect test connections and remove test pressure gauge.
11.1. Connect plug-in coupling for fuel lines.
11.2. The coupling must lock with an audible click. Pull to check that the connection is secure.
12. Switch off the ignition and remove PIWIS Tester adapter lead in the vehicle.
Checking fuel pressure - engine idling
Tools
Tool overview
1. Open the retaining clip for the fuel lines on the underbody and unclip the supply line.
1.1. To do this, open the clip using a small screwdriver.
Opening retaining clip on fuel lines
2. Open the rapid-action coupling on the fuel pressure line.
2.1. Wrap a cloth around the connection point (to prevent splashes), press the two locking lugs and pull the line apart.
Alternatively, relieve the fuel pressure. To do this, remove the fuse for the fuel pump, start the engine and leave it running until it stops.
Rapid-action coupling on fuel pressure line
3. Connect special tool test pressure gauge with lines from K-Jetronic Tester V.A.G. 1318 WE 1291 to the fuel line.
3.1. Engage pressure gauge on the transmission bracket using the chain.
3.2. Insert connection lines into the relevant couplings.
Test pressure gauge with connection lines (V.A.G. 1318) on the vehicle
4. Start the engine and read off the fuel pressure on the pressure gauge.
=> Fuel pressure - engine idling: 5.0 bar+/-0.3 bar
5. Switch off the engine after reading the fuel pressure.
6. Holding pressure test (if required):
=> Pressure: 4.0 bar
7. Disconnect test connections and remove test pressure gauge.
7.1. Connect plug-in coupling for fuel lines.
7.2. The coupling must lock with an audible click. Pull to check that the connection is secure.
Subsequent work
1. Remove the charger and fit the battery cover.
2. Remove the warning sign.
3. Start the vehicle and check the fuel line on the underbody for leaks.
4. Fit underbody panelling.
-> 519419 Removing and installing cover for rear underbody.
-> 519319 Removing and installing cover for centre underbody.