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EVAPorative emissions control (EVAP) system - general information, checking and component renewal
Emissions control systems / EVAPorative emissions control (EVAP) system - general information, checking and component renewal


General description
1 This system is fitted to minimise the escape of unburned hydrocarbons into the atmosphere. The fuel tank filler cap is sealed, and a charcoal canister is mounted underneath the tank, to collect and store petrol vapours generated in the tank when the vehicle is parked. When the engine is running, the vapours are cleared from the canister (under the control of the ECU via the canisterpurge solenoid valve) into the inlet tract, to be burned by the engine during normal combustion - see illustration 2.1A.

2 To ensure that the engine runs correctly when it is cold and/or idling, and to protect the catalytic converter from the effects of an over-rich mixture, the canister-purge solenoid valve is not opened by the ECU until the engine is fully warmed-up and running under part-load; the solenoid valve is then switched on and off, to allow the stored vapour to pass into the inlet.

Checking
3 Poor idle, stalling and poor driveability can be caused by an inoperative canister-purge solenoid valve, a damaged canister, split or cracked hoses, or hoses connected to the wrong fittings. Check the fuel filler cap for a damaged or deformed gasket.

4 Fuel loss or fuel odour can be caused by liquid fuel leaking from fuel lines, a cracked or damaged canister, an inoperative canisterpurge solenoid valve, and disconnected, misrouted, kinked or damaged vapour or control hoses.

5 Inspect each hose attached to the canister for kinks, leaks and cracks along its entire length. Repair or renew as necessary.

6 Inspect the canister. If it is cracked or damaged, renew it. Look for fuel leaking from the bottom of the canister. If fuel is leaking, renew the canister, and check the hoses and hose routing.

7 If the canister-purge solenoid valve is thought to be faulty, unplug its electrical connector and disconnect its vacuum hoses.

Connect a battery directly across the valve terminals. Check that air can flow through the valve passages when the solenoid is thus energised, and that nothing can pass when the solenoid is not energised. Alternatively, connect an ohmmeter to measure the resistance across the solenoid terminals, and compare this reading to the one listed in the Specifications Section at the beginning of this Chapter. Renew the solenoid valve if it is faulty.

8 Further testing should be left to a dealer service department.

Component renewal
Charcoal canister-purge solenoid valve
9 If better access is required, remove the plenum chamber (see Chapter 4). Disconnect the battery negative (earth) lead - see Section 1 of Chapter 5.

10 Unplug the valves electrical connector (see illustration). Unclip the valve from the bulkhead, then disconnect its vacuum hoses and withdraw it.

5.10 Charcoal canister-purge solenoid valve (arrowed) is clipped to bulkhead
5.10 Charcoal canister-purge solenoid valve (arrowed) is clipped to bulkhead behind engine

11 Refitting is the reverse of the removal procedure.

Charcoal canister - Saloon and Hatchback models
Note: Read through this procedure carefully before starting work, and ensure that the equipment is available that is required to carry it out safely and with minimum risk of damage, and to align the crossmember with sufficient accuracy on reassembly.

12 Remove the fuel tank (see Chapter 4).

13 Ensure that the rear of the vehicles body is supported securely on axle stands, then support the rear suspension crossmember with a jack. Remove the roadwheels and unscrew the rear suspension strut top mounting bolts (two per side - see Chapter 10).

14 Use white paint or similar (do not use a sharp-pointed scriber, which might break the underbody protective coating and cause rusting) to mark the exact relationship of the crossmember to the underbody. Unscrew the four mounting bolts (see illustration). Lower the crossmember approximately 3 inches (75 mm) on the jack, and support it securely.

5.14 Support rear suspension crossmember on jack, and remove mounting bolts
5.14 Support rear suspension crossmember on jack, and remove mounting bolts (arrowed) . . .

Warning: DO NOT place any part of your body under the vehicle when it is supported only by a jack!

15 Unscrew the two rearmost canister assembly retaining bolts (see illustration).

5.15 . . . lower crossmember by 3 inches, and unscrew charcoal canister
5.15 . . . lower crossmember by 3 inches, and unscrew charcoal canister assembly rear retaining bolts (arrowed) . . .

16 Unplug the two hoses from the canister assembly, noting which way round they are fitted (see illustration).

5.16 . . . unplug hoses (arrowed) from canister assembly . . .
5.16 . . . unplug hoses (arrowed) from canister assembly . . .

17 Unscrew the canister assemblys front retaining bolt (see illustration). Withdraw the canister assembly.

5.17 . . . and remove front retaining bolt (arrowed) to release canister
5.17 . . . and remove front retaining bolt (arrowed) to release canister assembly - Saloon and Hatchback models

18 Release the clip, and drive out the pin to separate the canister from its bracket (see illustration).

5.18 Release clip and drive out pin to separate canister from mounting
5.18 Release clip and drive out pin to separate canister from mounting bracket

19 On reassembly, refit the canister to its bracket and refit the assembly to the vehicle, tightening the retaining bolts securely, and ensuring that the two hoses are securely reconnected to their original unions.

20 Offer up the crossmember and refit the crossmember bolts, tightening them only lightly at this stage.

21 The crossmember must now be aligned on the underbody. Ford specify the use of service tool 15-097, which is a pair of tapered guides, with attachments to hold them in the crossmember as it is refitted (see illustration). However, since the working diameter of these tools is 20.4 mm, and since the corresponding aligning holes in the crossmember and underbody are 21 mm and 22 mm in diameter, there is a significant inbuilt tolerance possible in the crossmembers alignment, even if the correct tools are used. If these tools are not available, align the crossmember by eye, centring the crossmember aligning holes on those of the underbody, and using the marks made on removal for assistance. Alternatively, use a tapered drift such as a clutch-aligning tool, or a deep socket spanner of suitable size.

5.21 Refitting rear suspension crossmember with Ford service tools (arrowed)
5.21 Refitting rear suspension crossmember with Ford service tools (arrowed) in place to align it with underbody . . .

22 Once the crossmember is aligned as precisely as possible, tighten its bolts to the specified torque (see Chapter 10 Specifications) without disturbing its position (see illustration). Recheck the alignment once all the bolts are securely tightened.

5.22 . . . ensure aligned crossmember does not move - Ford tools used here -
5.22 . . . ensure aligned crossmember does not move - Ford tools used here - while mounting bolts are tightened

23 The remainder of the refitting procedure is the reverse of removal.

24 Remember that, since the rear suspension crossmember has been disturbed, the wheel alignment and steering angles must be checked fully and carefully as soon as possible, with any necessary adjustments being made. This operation is best carried out by an experienced mechanic using proper checking equipment; the vehicle should therefore be taken to a Ford dealer or similar for attention.

Charcoal canister - Estate models 25 Disconnect the battery negative (earth) lead - see Section 1 of Chapter 5.

26 Raise the rear of the vehicle, and support it securely on axle stands.

Warning: DO NOT place any part of your body under the vehicle when it is supported only by a jack!

27 Disconnect the two hoses from the canister assembly, noting which way round they are fitted.

28 Unscrew the canister assembly retaining bolt and withdraw the assembly, unclipping it from the front mounting.

29 Remove the plastic cover, and drive out the pin to separate the canister from its bracket (see illustration).

5.29 Charcoal canister assembly - Estate models - showing plastic cover
5.29 Charcoal canister assembly - Estate models - showing plastic cover (arrowed) and pin securing canister to mounting bracket

30 On refitting, secure the canister to its bracket, and refit the assembly to the vehicle.

Tighten the retaining bolt securely, and ensure that the two hoses are securely reconnected to their original unions.


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