Fuel Injectors For Injection Quantity and Proper Seal, Checking
Fuel Injection Volume, Fuel Injector Leakage and Spray Pattern of Injectors, Checking
WARNING!
Fire hazard! The fuel system is pressurized. Before loosening hose connections or opening the test connection (to measure fuel pressure), place a cloth around the connection. Then release pressure by carefully pulling off the hose or cap.
Test conditions
Fuel pressure OK; Testing and Inspection
To reach the fuel rail, the following steps must be performed on vehicles with manual transmission (without secondary air injection). On vehicles with automatic transmission (with secondary air injection) are minor differences in the work procedure.
- Unscrew bolts on air duct at points indicated (arrows) and remove air duct.
Several hoses must now be disconnected:
- Absolute cleanliness must be maintained.
- After completing test, use new hose clamps and make sure they are installed properly.
1 - Detach Wastegate Bypass Regulator Valve -N75 from fuel rail. The hoses must remain connected.
2 - Disconnect harness connector from EVAP Canister Purge Regulator Valve -N80.
3 - Disconnect harness connector from Recirculating valve for turbocharger -N249.
4 - Open hose clamps shown in the illustration and detach hoses from air recirculating valve.
5 - Open hose clamp on fuel pressure regulator and detach hose.
6 - Disconnect harness connectors from injectors on cylinder banks 1 and 2.
7 - Open hose clamp and detach hose (vacuum hose for applying vacuum to the mechanical air recirculating (Bypass) valves when required).
8 - Open hose clamps shown in the illustration and detach hoses. (The hoses lead to the intake (suction) sides of the turbochargers for cylinder banks 1 and 2).
9 - Open hose clamp shown in the illustration and detach hose. (The hose supplies fuel vapor to the intake manifold).
10 - Briefly open screw connection on fuel rail (supply hose) to release pressure. Use clean cloth to catch any fuel that leaks out. Then tighten screw connection again.
WARNING!
Fire hazard! The fuel system is pressurized. Before loosening hose connections or opening the test connection, place a cloth around the connection. Then release pressure by carefully pulling off the hose or cap.
11 - Unbolt fuel rail from intake manifold at the points indicated (see arrows).
- Tightening torque bolts: 10 Nm
- Lift fuel rail off intake manifold together with fuel injectors and support the fuel rail.
NOTE:
- After lifting off the fuel rail, check to make sure that the injectors are properly secured to the fuel rail.
- It is possible that some of the fuel injectors will become detached from the fuel rail and remain in the intake manifold when the fuel rail is removed. If this happens, install the fuel injectors back onto the fuel rail.
- Connect test box VAG 1598/31 to wiring harness for engine control unit. Do not connect to the engine control module itself. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1598/31 Test Box" Testing and Inspection
WARNING!
Make sure test box is inside of passenger compartment.
Checking for leaks
- Bridge sockets 1 and 65 on the test box using test leads from VAG1594 A connector test kit. (This creates an Ground (GND) connection to one side of the fuel pump relay coil.)
NOTE: Once the socket are bridged the fuel pump runs continuously, even if the engine is not running. This is because the fuel pump relay receives its positive voltage supply via the central electrics. The negative voltage supply for the fuel pump relay comes via the cable bridge on the test box.
WARNING!
Fire hazard. DO NOT smoke or work near heaters or have anything in the area that can ignite fuel!
- Check injectors fuel for leaks (visual check). When fuel pump is running, only 1 or 2 drops should escape per minute from each injector.
- If fuel loss is greater, switch off fuel pump (remove bridge) and replace faulty injector, also observe notes.
Checking injection quantity
- Place fuel injector which is to be tested into measuring glass from injection quantity tester VAG1602.
- Connect one fuel injector terminal to engine Ground (GND) using test cable and crocodile clamp from VAG1594 connector test kit.
- Connect second fuel injector terminal to B+ using remote control VAG1348/3 A, adapter cable VAG1348/3-2 and auxiliary cable.
WARNING!
Make sure test box is inside of passenger compartment.
- Bridge sockets 1 and 65 on the test box using test leads from VAG1594 A connector test kit. (This creates an Ground (GND) connection to one side of the fuel pump relay coil.)
The fuel pump should run.
- Activate remote control VAG1348/3 A for 30 seconds.
- When all three fuel injectors from the first bank of cylinders have been activated, place the three measuring glasses on a level surface.
Specification for each fuel injector: 135... 165 ml
- If measured value for one or more of fuel injectors is outside tolerance range, switch off fuel pump (switch ignition off) and replace faulty fuel injector, also observe notes.
- Repeat test for fuel injectors from second bank of cylinders.
- If measured values for all fuel injectors are outside tolerance range (specification), check fuel pressure. Testing and Inspection
NOTE: When checking the injection quantity, also check the spray pattern. The spray pattern should be the same for all the injectors.
Installation of the fuel rail together with injectors is performed in the reverse sequence. The following points should be noted when installing:
- Replace O-rings at all opened connections. (When replacing the front O-ring, make sure not to remove the plastic cap from the injector head. The O-ring must be pulled off over the plastic cap.)
- Moisten O-rings with clean engine oil.
- Make sure fuel injectors are correctly positioned, insert vertically into fuel rail and secure with retainer clips
- Position fuel rail together with injectors (properly secured) against intake manifold and press into place evenly all round.
- Replace hose clamps and make sure that they are securely installed.