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Fuel injection system/engine management system - check
Fuel and exhaust systems / Fuel injection system/engine management system - check


Warning: Petrol is extremely flammable, so extra precautions must be taken when working on any part of the fuel system. Do not smoke, or allow open flames or bare light bulbs, near the work area. DonТt work in a garage if a natural gas-type appliance with a pilot light is present. While performing any work on the fuel system, wear safety glasses, and have a dry chemical (Class B) fire extinguisher on hand. If you spill any fuel on your skin, rinse it off immediately with soap and water.

Note: This is an initial check of the fuel delivery and air induction sub-systems of the engine management system, to be carried out in conjunction with the operational check of the fuel pump (see Section 8), and as part of the preliminary checks of the complete engine management system (see Section 3 of Chapter 6).

1 Check the earth wire connections for tightness. Check all wiring and electrical connectors that are related to the system.

Loose electrical connectors and poor earths can cause many problems that resemble more serious malfunctions.

2 Check to see that the battery is fullycharged.

The ECU and sensors depend on an accurate supply voltage to properly meter the fuel.

3 Check the air filter element - a dirty or partially-blocked filter will severely impede performance and economy (see Chapter 1).

4 If a blown fuse is found, renew it and see if it blows again. If it does, search for a shortcircuited wire in the harness related to the system (see Chapter 6).

5 Check the air intake duct from the intake to the inlet manifold for leaks, which will result in an excessively-lean mixture. Also check the condition of the vacuum hoses connected to the inlet manifold.

6 Remove the plenum chamber from the throttle housing. Check the throttle valve for dirt, carbon or other residue build-up. If itТs dirty, seek the advice of a Ford dealer - since the electronic control system is designed to compensate for factors such as the build-up of dirt in the throttle housing, it may well be best to leave it dirty, unless the deposits are extensive. Note: A warning label on the housing states specifically that the housing bore and the throttle valve have a special coating, and must not be cleaned using carburettor cleaner, as this may damage it.

7 With the engine running, place a screwdriver or a stethoscope against each injector, one at a time. Listen through the screwdriver handle or stethoscope for a clicking sound, indicating operation.

8 If an injector isnТt operating (or sounds different from the others), turn off the engine, and unplug the electrical connector from the injector. Check the resistance across the terminals of the injector, and compare your reading with the resistance value listed in this ChapterТs Specifications. If the resistance isnТt as specified, renew the injector.

9 A rough idle, diminished performance and/or increased fuel consumption could also be caused by clogged or fouled fuel injectors.

Fuel additives that can sometimes clean fouled injectors are available at car accessory shops.

10 The remainder of the system checks should be left to a dealer service department or other qualified repair specialist, as there is a chance that the ECU may be damaged if tests are not performed properly.


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