Fuel Pressure: Testing and Inspection
Checking Fuel Pressure
Tools
Preliminary work
1. Open the bonnet.
2. Open lid of central electrics box. To do this, loosen the four fastening screws.
3. Remove fuses -3- for the ignition rod modules, -4- injection system and both fuel pump relays (left pump -1- and right pump -2-).
4. Pull the design cover up and off.
Tools and materials
Special tools
Test conditions
- The battery voltage must not be < 12 volts.
- Fuel system parts must not get dirty.
Checking fuel pressure
DANGER:
Danger of poisoning from fuels.
- Gasoline is toxic.
- Inhaling vapours can cause irritation of the mucous membranes and eyes.
- It can be carcinogenic. It represents a serious risk to health when inhaled, touched or swallowed over longer periods.
- Only work on the fuel system in well-ventilated rooms.
- Wear protective gloves that are fuel-resistant.
- Wear a breathing mask with active charcoal filter; do not breathe in any fuel vapours.
- Ensure that there is adequate ventilation and extract all fuel vapours.
- Before opening the fuel lines or fuel hoses, relieve the fuel pressure.
- Collect escaping fuel, absorb it if necessary with a suitable binding material and dispose of properly.
- Pay attention to cleanliness when working on the fuel system.
DANGER:
Danger of fire from fuel.
- Keep clear of ignition sources.
- Do not smoke.
- Disconnect battery.
- Danger of fire due to naked flames and sparks, e.g. during welding or grinding work.
- Danger of fire due to escaping fuel, e.g. on hot engine components or due to electrostatic charge. Allow engine to cool down.
- Secure the vehicle, e.g. with a warning sign.
- Change any clothing soaked with fuel immediately.
- In case of fire, use CO2 or dry powder fire extinguishers.
NOTE:
- The ignition must be switched off when working on the fuel system.
- Absorb any escaping fuel using a suitable binding material or a cloth.
- Cloths which have absorbed fuel must be disposed of according to the applicable national laws.
- The fuel system must be depressurised before starting work on it.
- Only work on the fuel system in well-ventilated rooms.
- Any seals which have been removed must always be replaced.
- The fuel gallery is pressurised. Place a cloth under the areas of the fuel gallery to be opened so that fuel does not drip on to hot engine parts.
1. Twist off the cap of the fuel scavenging valve -1-.
NOTE: Make sure that the switch on the adapter 9479 is at 0 so that fuel is not pumped immediately when you connect the adapter.
2. Insert adapter 9479 into both relay slots of the fuel pump relay for the fuel supply pumps at the same time.
NOTE: Proceed as follows to fit the adapter 1318/20 -2- to the scavenging valve: Turn the valve -4- anti-clockwise at the T-piece until the valve is closed. Place the adapter on the scavenging valve and use the knurled nut -3- to fit the adapter in a clockwise direction until the adapter is attached securely to the scavenging valve. To open the scavenging valve, turn the T-piece of the valve clockwise (the fuel is released immediately and flows out via the adapter 1318/20). If the, T-piece touches the intake-air distributor when you turn it, shorten the cross-pin of the T-piece slightly so that it has sufficient clearance. The adapter 1318/20 includes a hose connection 1318/20-1 -1-, to which a suitable fuel hose can be fitted using a screw-type clamp.
3. Fit adapter 1318/20 to the scavenging valve (valve closed) -1-. Fit the tool set VAG 1318 to the adapter and support pressure gauge on the bonnet lock -3-. Keep the valve closed with the stop-cock -5- under the pressure gauge (stop-cock is positioned at a right angle to the flow direction). Fit hose connection 1318/20-1 -4- to the stop-cock and route a suitable fuel hose into a measuring cup using a clamp. The tool must be assembled as shown.
NOTE: The steady-state pressure must be greater than 3.0 bar after 10 minutes.
4. Screw the valve (T-piece) in clockwise at the adapter 1318/20. Set the stop-cock under the pressure gauge VAG 1318 to flow direction. Switch on both fuel pumps for a short time using the adapter 9479 in order to rinse out the air. Close the stop-cock under the pressure gauge VAG 1318 (stop-cock is positioned at a right angle to the flow direction). Switch on both fuel pumps using the adapter 9479 and read the pressure on the pressure gauge. The fuel pressure should be approx. 4.0 bar. Then switch off both fuel pumps and check the steady-state pressure. The fuel pressure must not drop below 3.0 bar after 10 minutes.
Subsequent work
1. Insert fuses -3- for the ignition rod modules, -4- injection system and both fuel pump relays (left pump -1- and right pump -2-).
2. Fit lid of central electrics box. To do this, fit the four fastening screws.
3. Fit the design cover.