Digifant fuel injection system components - removal and refitting

Fuel system: multi-point injection models / Digifant fuel injection system components - removal and refitting

Air flow meter
Removal
1 Disconnect the battery negative cable and position it away from the terminal.

2 With reference to Section 2 and Chapter 1, remove the top cover from the air cleaner assembly.

3 Unplug the harness connector from the air flow meter.

4 Remove the retaining screws and detach the meter from the air cleaner top cover - recover the seal (see illustration).

5.4 Remove the air flow meter retaining screws (at-rowed)

Caution: Handle the air flow meter carefully - its internals are easily damaged.

Refitting
5 Refitting is a reversal of removal. Renew the seal if it appears damaged.

Throttle valve potentiometer (engine code 3F only)
Removal
6 Disconnect the battery negative cable and position it away from the terminal.

7 Unplug the harness connector from the potentiometer (see illustration).

5.7 Unplug the wiring harness from the potentiometer at the connector (arrowed)

8 Remove the retaining screws and locking plate, then lift the potentiometer away from the throttle body. Recover the O-ring seal.

Refitting
9 Refitting is a reversal of removal, noting the following:
a) Renew the O-ring seal if it appears damaged.

b) Ensure that the potentiometer drive engages correctly with the throttle spindle extension.

I O On completion, the potentiometer must be “matched” electronically to the Digifant Electronic Control Unit (ECU). This operation requires access to dedicated electronic test equipment, refer to a VW dealer for advice.

Inlet air temperature sensor Removal
11 The sensor is an integral part of the air flow meter and cannot be renewed separately (see illustration).

5.11 The inlet air temperature sensor (arrowed) is an integral part of the air flow meter

Auxiliary air valve
Removal
12 The valve is mounted on a bracket below the inlet manifold - access is extremely limited with the inlet manifold in position.

13 Unplug the harness connector from the valve.

14 Release the clips and disconnect the hoses from the auxiliary valve. Note their order of connection to aid correct refitting.

15 Remove the screw and detach the valve from its mountings.

Refitting
16 Refitting is a reversal of removal.

Coolant temperature sensor Removal
17 The coolant temperature sensor is mounted at the left hand side of the cylinder head, directly underneath the ignition distributor. Two sensors are fitted; the one colour coded blue serves the engine management system, the black one produces a signal for the instrument panel temperature gauge (see illustration).

5.17 Two coolant temperature sensors are fitted; the one colour coded blue (arrowed) serves the engine management system

18 Unplug the harness connector from the sensor.

19 Refer to Chapter 3 and drain approximately one quarter of the coolant from the engine.

20 Extract the retaining clip and lift the sensor from the coolant elbow - be prepared for coolant loss. Recover the O-ring.

Refitting
21 Refit the sensor by reversing the removal procedure, using a new O-ring. Refer to Chapter 1 and top-up the cooling system.

Engine speed Hall sender 22 This sensor is an integral part of the ignition HT distributor assembly. It can be removed and renewed separately, but dismantling of the distributor will be necessary. It is therefore recommended that this operation is entrusted to a automotive electrical specialist.

Throtte body
Removal
23 Refer to Section 4 and detach the accelerator cable from the throttle valve lever.

24 Slacken the clips and detach the inlet air ducting from the top of the throttle body inlet.

Remove the bolts, lift off the throttle body inlet elbow and recover the seal (see illustrations).

5.24a Slacken the clips and detach the inlet air ducting from the top of the throttle body inlet

5.24b Remove the bolts, lift off the throttle body inlet elbow . , .

5.24c . . . and recover the seal

25 On engine code 3F, remove the throughbolt and detach the inlet housing from the top of the throttle body. On engine code PY, remove the screws and detach the bypass valve housing from the top of the throttle body.

26 Disconnect the battery negative cable and position it away from the terminal, then unplug the harness connector from the throttle potentiometer.

27 Disconnect the vacuum hoses from the ports on the throttle body, noting their order of fitment. Release the wiring harness from the guide clip.

28 Slacken and withdraw the bolts (see illustration), then lift the throttle body away from the inlet manifold. Recover and discard the gasket.

5.28 Slacken and withdraw the four throttle body retaining bolts (three arrowed, one hidden)

Refitting
29 Refitting is a reversal of removal, noting the following:
a) Use a new throttle body-to-inlet manifold gasket.

b) Observe the correct tightening torque when refitting the throttle body throughbolts/ screws.

c) Ensure that all vacuum hoses and electrical connectors are refitted securely.

d) With reference to Section 4, check and if necessary adjust the accelerator cable.

Fuel injectors and fuel rail Warning: Observe the
precautions in Section 1 before working on any component in the fuel system. Ideally this operation should be carried out when the engine is cold.

Removal
30 Disconnect the battery negative cable and position it away from the terminal.

31 Refer to the relevant sub-Section in this Chapter and remove the throttle body.

32 Unplug the injector wiring harness at the multiway connector, which is located at the end of the fuel rail (see illustration).

5.32 Unplug the injector wiring harness at the multiway connector

33 Refer to Section 8 and depressurise the fuel system.

34 Disconnect the vacuum hose from the port on the top of the fuel pressure regulator (see illustration).

5.34 Disconnect the vacuum hose from the top of the fuel pressure regulator

35 Slacken the clips and disconnect the fuel supply and return hoses from the ports on the fuel rail and pressure regulator (see illustrations). Carefully note the fitted positions of the hoses - the supply hose is colour-coded black and the return hose is colour-coded with a blue band.

5.35a Slacken the clips and disconnect the fuel supply hose. . .

5.35b . . . and return hose (arrowed)

36 Slacken and withdraw the fuel rail retaining screws, then carefully lift the fuel rail away from the inlet manifold, together with the injectors. Recover the injector lower O-ring seals as they emerge from the manifold, if they work loose (see illustrations).

5.36a Slacken and withdraw the fuel rail retaining screws (art-owed) . . .

5.36b . . . then carefully lift the fuel rail away from the inlet manifold, together with the injectors

37 To remove individual injectors from the fuel rail, proceed as follows (see illustrations):

5.37a Unclip both halves of the plastic shielding from the injector body

5.37b Remove the insulating shroud

5.37c Unplug the wiring harness connector

5.37d Extract the retaining clip

5.37e Prise out the injector

5.37f Fuel rail, injector and fuel pressure regulator assembly (No 1 injector removed)

1 Fuel pressure regulator 2 Fuel rail
3 Fuel injectors
4 Fuel pressure test point

5.37g Injector O-rings (arrowed)

a) Unclip both halves of the plastic shielding from the injector body.

b) Remove the insulating shroud.

c) Unplug the wiring harness connector.

d) Extract the retaining clip.

e) Prise out the injector.

38 If required, remove the fuel pressure regulator, referring to the relevant sub-Section for guidance.

39 Check the electrical resistance of the injectors using a multimeter connected across the injector terminals - compare the results with the Specifications.

40 Moisten the injector O-rings with clean engine oil, then refit the injectors to the fuel rail, ensuring that the O-ring seals are correctly seated and that the retaining clips are firmly in place.

Refitting
41 Refit the injectors and fuel rail by following the removal procedure in reverse, noting the following points:
a) Renew the injector O-ring seals if they appear worn or damaged.

b) Ensure that the injector retaining clips are securely seated.

c) Check that the fuel supply and return hoses are reconnected correctly - refer to the colour coding described in “Removal”.

d) Check that all vacuum and electrical connections are remade correctly and securely.

e) On completion, check exhaustively for fuel leaks before bringing the vehicle back in to service.

Fuel pressure regulator
Warning: Observe the
precautions in Section 1 before working on the fuel system.

ideally this operation should be carried out when the engine is cold.

Removal
42 Disconnect the battery negative cable and position it away from the terminal.

43 Refer to Section 8 and depressurise the fuel system.

44 Disconnect the vacuum hose from the port on the top of the fuel pressure regulator.

45 Slacken the clip and disconnect the fuel supply hose from the end of the fuel rail. This will allow the majority of fuel in the regulator to drain out. Be prepared for an amount of fuel loss - position a small container and some old rags underneath the fuel regulator housing.

46 Remove the retaining screws and lift off the regulator body, recovering the O-ring seal (see illustration).

5.45 Remove the retaining screws (arrowed) and lift off the regulator body

Refitting
47 Refit the fuel pressure regulator by following the removal procedure in reverse, noting the following points.

a) Renew the O-ring seals if they appear worn or damaged
b) Ensure that the regulator retaining screws are tightened to the correct torque.

c) Refit the regulator vacuum hose securely.

Lambda sensor
Removal
48 The Lambda sensor is threaded into the exhaust pipe, at the front of the catalyst (see illustration).

5.48 The Lambda sensor (arrowed) is threaded into the exhaust pipe, at the front of the catalyst

49 Disconnect the battery negative cable and position it away from the terminal, then unplug the wiring harness from the Lambda sensor at the connector, located at the rear of the engine, beneath the throttle body (see illustration).

5.49 Unplug the wiring harness from the Lambda sensor at the connector (arrowed), mounted at the rear of the engine, on the side of the inlet manifold

50 Note: As a flying lead remains connected to the sensor after is has been disconnected, if the correct size spanner is not available, a slotted socket will be required to remove the sensor. Working under the vehicle, slacken and withdraw the sensor, taking care to avoid damaging the sensor probe as it is removed.

Refitting
51 Apply a little anti-seize grease to the sensor threads - take care to avoid contaminating the probe tip.

52 Refit the sensor to its housing, tightening it to the correct torque. Restore the harness connection.

Electronic Control Unit (ECU) Removal
Caution: Electronic Control Units (ECUs) contain components that are sensitive to the levels of static electricity generated during normal activity. Once the multiway harness connector has been unplugged, the exposed ECU connector pins can freely conduct stray static electricity to these components, damaging or even destroying them - the damage will be invisible and may not manifest itself immediate/y. Expensive repairs can be avoided by observing the following basic handling rules: a) Handle a disconnected ECU by its case only; do not allow fingers or tools to come into contact with the pins.

b) When carrying an ECU around, “‘ground” yourself from time to time, by touching a metal object such as an unpainted water pipe, this will discharge any potentially damaging static that may have built up.

c) Do not leave the ECU unplugged from its connector for any longer than is absolutely necessary.

d) Do not ‘test’ the ECU using multimeters or other non-dedicated test equipment.

e) Only unplug the ECU connector after the battery supply has been disconnected.

53 The ECU is located on the engine bulkhead, beneath a water shield.

54 Disconnect the battery negative cable and position it away from the terminal.

55 Remove the clips and lift off the water shield.

56 Release the spring clip and unplug the multiway connector from the ECU.

57 Remove the screws and lift the ECU away from the mounting bracket (see illustration).

5.57 Remove the securing screws and lift the ECU away from the mounting bracket

Refitting
58 Refitting is a reversal of removal.

Fuel pump relay
59 The fuel pump relay is located on the engine bulkhead, beneath a water shield. It is the lower of the two relays mounted on the same bracket as the engine management system ECU.

60 Disconnect the battery negative cable and position it away from the terminal.

61 Remove the clips and lift off the water shield.

62 Pull the relay from its socket.

63 Refitting is a reversal of removal.