Chapter 1 Routine maintenance and servicing

Fuel system - electronic fuel injection engines 4C•3Engine temperature information is suppliedby the coolant temperature sensor. Thiscomponent is an NTC (Negative TemperatureCoefficient) thermistor - that is, a semiconductorwhose electrical resistancedecreases as its temperature increases. Itprovides the EEC IV module with a constantlyvarying(analogue) voltage signal, correspondingto the temperature of the enginecoolant. This is used to refine the calculationsmade by the module, when determining thecorrect amount of fuel required to achieve theideal air/fuel mixture ratio.Inlet air temperature information is suppliedby the inlet air temperature sensor. Thiscomponent is also an NTC thermistor - see theprevious paragraph - providing the module witha signal corresponding to the temperature of airpassing into the engine. This is used to refinethe calculations made by the module, whendetermining the correct amount of fuel requiredto achieve the ideal air/fuel mixture ratio.A throttle position sensor is mounted on theend of the throttle valve spindle, to providethe EEC IV module with a constantly-varying(analogue) voltage signal corresponding to thethrottle opening. This allows the module toregister the driver’s input when determiningthe amount of fuel required by the engine.Road speed is monitored by the vehiclespeed sensor. This component is a Hall-effectgenerator, mounted on the transmission’sspeedometer drive. It supplies the module with aseries of pulses corresponding to the vehicle’sroad speed, enabling the module to controlfeatures such as the fuel shut-off on overrun.A manifold absolute pressure sensormeasures inlet manifold vacuum, and suppliesthis information to the EEC IV module forcalculation of engine load at any given throttleposition.Where power steering is fitted, a pressureoperatedswitch is screwed into the powersteering system’s high-pressure pipe. Theswitch sends a signal to the EEC IV module toreduce engine speed should the power steeringfluid pressure become excessively high.On models with a catalytic converter, theoxygen sensor in the exhaust system providesthe EEC IV module with constant feedback -“closed-loop” control - which enables it toadjust the mixture to provide the best possibleconditions for the catalytic converter to operate.On turbocharged engines, control of theturbocharger boost pressure is also governedby the EEC IV module, acting through theboost control valve. This allows inlet manifolddepression to be applied to the turbochargerwastegate control.The turbocharger consists of a turbine thatis driven by the exhaust gases, to suck airthrough the air filter and to compress it into theengine. An air-cooled intercooler, mountednext to the radiator, cools the inlet air (heatedby its passage through the turbocharger); thisincreases the density of the compressedfuel/air mixture entering the engine, thusimproving the engine’s power output.PrecautionsWarning: Petrol is extremelyflammable - great care must betaken when working on any partof the fuel system. Do notsmoke or allow any naked flames oruncovered light bulbs near the work area.Note that gas powered domesticappliances with pilot flames, such asheaters, boilers and tumble dryers, alsopresent a fire hazard - bear this in mind ifyou are working in an area where suchappliances are present. Always keep asuitable fire extinguisher close to the workarea and familiarise yourself with itsoperation before starting work. Wear eyeprotection when working on fuel systemsand wash off any fuel spilt on bare skinimmediately with soap and water. Notethat fuel vapour is just as dangerous asliquid fuel; a vessel that has just beenemptied of liquid fuel will still containvapour and can be potentially explosive.Petrol is a highly dangerous and volatileliquid, and the precautions necessarywhen handling it cannot be overstressed.Many of the operations described in thisChapter involve the disconnection of fuellines, which may cause an amount of fuelspillage. Before commencing work, referto the above Warning and the informationin “Safety first” at the beginning of thismanual.When working with fuel systemcomponents, pay particular attention tocleanliness - dirt entering the fuel systemmay cause blockages which will lead topoor running.Note: Residual pressure will remain in the fuellines long after the vehicle was last used,when disconnecting any fuel line, it will benecessary to depressurise the fuel system asdescribed in Section 2.Note: Refer to Section 16 for specificprecautions relating to turbocharged engines.2 Fuel system -depressurisation 1Refer to Part B, Section 2.4.6 Air cleaner housing attachmentsA Bolts B Grommet3 Fuel lines and fittings -general informationRefer to Part B, Section 3.4 Air cleaner assembly and airinlet components - removaland refitting1Note: Air cleaner element renewal and aircleaner temperature control system checks(where applicable) are described in Chapter 1.Air cleaner assembly1 Disconnect the battery negative (earth) lead(refer to Chapter 5A, Section 1).2 If the idle speed control valve is mountedon the air cleaner, disconnect the multi-plugand the air bypass hose from the valve.3 Disconnect the flexible hose between theair cleaner lid and the air inlet duct orturbocharger air inlet.4 Disconnect the crankcase breather hosefrom the front of the air cleaner housing.5 Unclip and remove the air cleaner lid, thenwithdraw the element.6 Remove the two bolts securing the forwardend of the air cleaner housing, free therearward end of the housing from its locationand carefully withdraw from the vehicle (seeillustration).7 Refitting is a reversal of the removalprocedure.Air inlet components8 Disconnect the battery negative (earth) lead(refer to Chapter 5A, Section 1).9 If the idle speed control valve is mountedon the air cleaner, disconnect the multi-plugand the air bypass hose from the valve (seeillustration).10 Disconnect the HT leads from the sparkplugs, labelling them if necessary to avoidconfusion on refitting.4.9 General view of the air inletcomponents on non-Turbo modelsA Air inlet ductB Air inlet duct securing boltsC Spark plug HT lead connectorsD Air cleaner lidE Idle speed control valve multi-plugF Air bypass hose4C1595Ford Fiesta Remake