Checking Fuel Pressure In the Low-Pressure System

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.
- 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.
3. Remove underbody panelling.

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.
- 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:







Alternative tool (can only be used when the engine is stopped):







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.

2. Run the individual control unit search for DME.







2.1. To do this, select DME and press F12>>.







3. After running the individual control unit search for DME, select Special functions.
3.1. Select the menu item Drain tank.







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.







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.

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.







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.







7. Activate the Drain tank (= activate fuel pump) function on the PIWIS Tester 9718 by pressing F8 Start.
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.

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







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.

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.

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.

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.