Checking Fuel Pressure In the Low-Pressure System
Checking Fuel Pressure In The Low-Pressure System
Tools
Technical values
Preliminary work
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.
INFORMATION:
- The battery voltage must not fall below 12.5 volts during the fuel pressure check.
- Connect a 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 material
- Danger of fire or explosion
- Avoid contact with hot parts or sources of ignition.
- Use suction to remove ignitable vapors.
- Attach warning sign in a clearly visible position.
2. Attach or mount a warning sign in a clearly visible position on the vehicle.
3. Reduce the fuel pressure in the low-pressure system.
3.1. Remove cover on fuse carrier (driver's side, bottom left).
3.2. Remove fuse for the fuel pump at the fuse carrier.
First fuse from the left, row D (see information in the cover of the fuse carrier).
3.3. Start the engine and allow to run until it cuts out.
3.4. Re-insert the fuse. Clip in cover.
Checking fuel pressure - engine stopped
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 vapors.
- 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 Drain tank in the menu and press F12 >>.
3.2. Read instructions on how to proceed, then press F12 >>
4. Remove underbody panelling.
5. Open fuel supply line -1- at the underbody.
5.1. To do this, press the two locking lugs and pull the plug-in coupling apart.
5.2. Collect emerging residual fuel.
6. Connect test pressure gauge and lines to the fuel lines.
6.1. Insert connection lines into the relevant couplings.
6.2. Secure pressure gauge -1- to a fixed component using the chain.
7. Alternatively, the test can be performed using the pressure gauge 378a.
7.1. To do this, connect connection line 17 to the plug-in coupling for the fuel tank.
INFORMATION:
- The battery voltage must not fall below 12.5 volts during the fuel pressure check.
- Connect a battery charger.
8. Activate the Drain tank (= activate fuel pump) function on the PIWIS Tester 9718 by pressing F8 Start.
9. Read off the pressure shown on the pressure gauge.
- Fuel pressure - engine not running: 5.0 bar ± 0.3 bar
10. Deactivate the Drain tank function by pressing F8 Stop.
10.1. Then, press F11 << a number of times to get to the start screen and switch off the Tester.
10.2. Switch off ignition.
11. Holding pressure test:
- Pressure: 4.0 bar
12. Pull off test connections and remove test pressure gauge.
12.1. Connect plug-in coupling for fuel lines.
12.2. The coupling must lock with an audible click. Pull to check that the connection is secure.
Checking fuel pressure - engine idling
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 vapors.
- Attach warning sign in a clearly visible position.
INFORMATION:
- The battery voltage must not fall below 12.5 volts during the fuel pressure check.
- Connect a battery charger.
1. Remove underbody panelling.
2. Open fuel supply line -1- at the underbody.
2.1. To do this, press the two locking lugs and pull the plug-in coupling apart.
2.2. Collect emerging residual fuel.
3. Connect test pressure gauge and lines to the fuel lines.
3.1. Insert connection lines into the relevant couplings.
3.2. Secure pressure gauge -1- to a fixed component using chain.
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. Pull off test connections and remove test pressure gauge.
7.1. Connect plug-in coupling for fuel supply line -1-.
7.2. The coupling must lock with an audible click. Pull to check that the connection is secure.
Subsequent work
1. Fit underbody cover.
2. Disconnect battery charger.
3. Remove warning sign.