Chapter 1 Routine maintenance and servicing

1595Ford Fiesta Remake5B•2 Ignition systemIgnition timing1.4 and 1.6 litre carburettor models with distributor:For use with 4-star leaded petrol (97 RON) . . . . . . . . . . . . . . . . . . . . 12° BTDC at idle speed (vacuum pipe disconnected and plugged)For use with unleaded petrol (95 or 98 RON) . . . . . . . . . . . . . . . . . . . 8° BTDC at idle speed (vacuum pipe disconnected and plugged)1.4 litre CFi fuel injection models with distributor (pre-Sept 1990) . . . . 10° BTDC at idle speed (set using STAR test equipment - refer to text)All other models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Totally controlled by ignition module or EEC IV engine managementmoduleSpark plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .See Chapter 1 SpecificationsTorque wrench settings Nm lbf ftCrankshaft position sensor (all engines except Zetec) . . . . . . . . . . . . . . 3 to 4 2 to 3Crankshaft position sensor to bracket (Zetec engines) . . . . . . . . . . . . . 7 to 9 5 to 7Crankshaft position sensor bracket to engine (Zetec engines) . . . . . . . 18 to 23 13 to 17DIS/E-DIS ignition coil to bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 to 7 4 to 5DIS/E-DIS ignition coil bracket to engine (all engines except Zetec) . . . 9 to 12 7 to 9DIS/E-DIS ignition coil bracket to engine (Zetec engines) . . . . . . . . . . . 18 to 23 13 to 171 General information andprecautionsGeneral informationThe ignition system is responsible forigniting the air/fuel mixture in each cylinder, atthe correct moment in relation to enginespeed and load, as the electrical sparkgenerated jumps the spark plug gap.The ignition system is based on feeding lowtension (LT) voltage from the battery to theignition coil where it is converted to hightension (HT) voltage. The high tension voltageis powerful enough to jump the spark pluggap in the cylinders many times a secondunder high compression pressures, providingthat the system is in good condition.A number of different ignition systems havebeen fitted to Fiesta models depending on theyear of manufacture, type of fuel system fittedand the emission level that the vehicle hasbeen designed to meet. Broadly speaking thesystems can be sub-divided into twocategories - distributor ignition systems anddistributorless ignition systems.One version of the distributor ignitionsystem is fitted to all CVH engines withcarburettors. A second (more sophisticated)version is fitted to pre-September 1990 CVHengines with CFi fuel injection.Distributorless ignition systems are fitted toall HCS, PTE and Zetec engines, and to allCVH engines with fuel injection except pre-September 1990 CFi versions.Distributor ignition systems (CVHengines with carburettor)The ignition system is divided into twocircuits; low tension (primary) and hightension (secondary). The low tension circuitconsists of the battery, ignition switch, coilprimary windings, ignition amplifier moduleand the signal generating system inside thedistributor. The signal generating systemcomprises the trigger coil, trigger wheel,stator, permanent magnet and trigger coil toignition amplifier module connector. The hightension circuit consists of the coil secondarywindings, the HT lead from the coil to thedistributor cap, the distributor cap, the rotorarm, the HT leads from the distributor cap tothe spark plugs and the spark plugsthemselves.When the system is in operation, lowtension voltage is changed in the coil into hightension voltage by the action of the electronicamplifier module in conjunction with the signalgenerating system. Any change in themagnetic field force (flux), created by themovement of the trigger wheel relative to themagnet, induces a voltage in the trigger coil.This voltage is passed to the ignition amplifiermodule which switches off the ignition coilprimary circuit. This results in the collapse ofthe magnetic field in the coil whichgenerates the high tension voltage. The hightension voltage is then fed, via the coil HTlead and the carbon brush in the centre of thedistributor cap, to the rotor arm. The voltagepasses across to the appropriate metalsegment in the cap and via the spark plug HTlead to the spark plug where it finally jumpsthe spark plug gap to earth.The distributor is driven by an offset drivedog locating to a correspondingly offset slotin the end of the camshaft.The ignition advance is a function of thedistributor and is controlled both mechanicallyand by a vacuum operated system. Themechanical governor mechanism consists oftwo weights which move out from thedistributor shaft as the engine speed rises dueto centrifugal force. As they move outwards,they rotate the trigger wheel relative to thedistributor shaft and so advance the spark.The weights are held in position by two lightsprings and it is the tension of the springswhich is largely responsible for correct sparkadvancement.The vacuum control consists of adiaphragm, one side of which is connectedvia a small bore hose to the carburettor orthrottle housing, and the other side to thedistributor. Depression in the inlet manifoldand/or carburettor, which varies with enginespeed and throttle position, causes thediaphragm to move, so moving the stator andadvancing or retarding the spark. A finedegree of control is achieved by a spring inthe diaphragm assembly.Additionally, one or more vacuum valvemay be incorporated in the vacuum linebetween the inlet manifold or carburettor andthe distributor. The function of these is tocontrol the vacuum felt at the distributor andto prevent fuel entering along the vacuum line(as applicable).Distributor ignition systems (pre-September 1990 CVH engines withCFi fuel injection)The ignition system is divided into twocircuits; low tension (primary) and hightension (secondary). The low tension circuitconsists of the battery, ignition switch, ignitionmodule, ballast resistor, coil primary windingsand “Hall effect” distributor. The high tensioncircuit consists of the coil secondarywindings, coil-to-distributor cap HT lead,distributor cap, rotor arm, spark plug HT leadsand spark plugs. The system is under theoverall control of the EEC IV enginemanagement module which also controls thefuel injection and emission control equipment.When the system is in operation thedistributor supplies the EEC IV module with acrankshaft position reference signal to enablean initial ignition timing setting to beestablished. This signal is generated bymeans of a trigger vane attached to thedistributor shaft and which rotates in the gapbetween a permanent magnet and a sensor.The trigger vane has four cut-outs, one foreach cylinder. When one of the trigger vanecut-outs is in line with the sensor, magnetic