Chapter 5 Engine electrical systems - Ford Sierra Net

Engine electrical systems 5•5Never disconnect the battery terminals, oralternator multi-plug connector, when theengine is running.The battery leads and alternator multi-plugmust be disconnected before carrying out anyelectric welding on the car.Never use an ohmmeter of the typeincorporating a hand cranked generator forcircuit or continuity testing.Ignition and engine managementsystemsWarning: The HT voltagegenerated by an electronicignition system is extremelyhigh, and in certaincircumstances could prove fatal. Take careto avoid receiving electric shocks from theHT side of the ignition system. Do nothandle HT leads, or touch the distributoror coil when the engine is running. Iftracing faults in the HT circuit, use wellinsulated tools to manipulate live leads.Engine management modules are verysensitive components, and certainprecautions must be taken to avoid damageto the module when working on a vehicleequipped with an engine management systemas follows.When carrying out welding operations onthe vehicle using electric welding equipment,the battery and alternator should bedisconnected.Although underbonnet-mounted modules(all except EEC IV) will tolerate normalunderbonnet conditions, they can beadversely affected by excess heat or moisture.If using welding equipment or pressurewashing equipment in the vicinity of themodule, take care not to direct heat, or jets ofwater or steam at the module. If this cannot beavoided, remove the module from the vehicle,and protect its wiring plug with a plastic bag.Before disconnecting any wiring, orremoving components, always ensure that theignition is switched off.On models with underbonnet-mountedmodules, do not run the engine with the moduledetached from the body panel, as the body actsas an effective heat sink, and the module maybe damaged due to internal overheating.Do not attempt to improvise fault diagnosisprocedures using a test lamp or multimeter,as irreparable damage could be caused to themodule.After working on ignition/enginemanagement system components, ensurethat all wiring is correctly reconnected beforereconnecting the battery or switching on theignition.On some early Bosch distributors it ispossible that with the distributor cap removed,if the engine is cranked, the cap securing clipsmay fall inward and jam the triggerwheel/vane, knocking it out of alignment. If thishappens, the distributor will have to berenewed as the trigger wheel/vane cannot berepositioned. Care should therefore be takennot to crank the engine with the distributor capremoved. Later distributors have redesignedclips which eliminate the problem.2 Battery - removal and refittingRemoval1 The battery is located in the enginecompartment on the left-hand side of thebulkhead.2 Disconnect the leads at the negative (earth)terminal by unscrewing the retaining nut andremoving the bulb. Pull off the plastic cover,and disconnect the positive terminal leads inthe same way.3 Unscrew the clamp bolt sufficiently toenable the battery to be lifted from its location(see illustration). Keep the battery in anupright position to avoid spilling electrolyte onthe bodywork.Refitting4 Refitting is a reversal of removal, but smearpetroleum jelly on the terminals whenreconnecting the leads, and always connectthe positive lead first and the negative lead last.3 Battery - testing and chargingTestingStandard and low maintenance battery1 If the vehicle covers a small annual mileageit is worthwhile checking the specific gravityof the electrolyte every three months todetermine the state of charge of the battery.Use a hydrometer to make the check andcompare the results with the following table.Ambient temperature:above 25ºC below 25ºCFully charged 1.21 to 1.23 1.27 to 1.2970% charged 1.17 to 1.19 1.23 to 1.25Fully discharged 1.05 to 1.07 1.11 to 1.13Note that the specific gravity readings assumean electrolyte temperature of 15ºC (60ºF); forevery 10ºC (50ºF) below 15ºC (60ºF) subtract0.007. For every 10ºC(50ºF) above 15ºC(60ºF)add 0.007.2 If the battery condition is suspect firstcheck the specific gravity of electrolyte ineach cell. A variation of 0.040 or morebetween any cells indicates loss of electrolyteor deterioration of the internal plates.3 If the specific gravity variation is 0.040 ormore, the battery should be renewed. If thecell variation is satisfactory but the battery isdischarged, it should be charged asdescribed later in this Section.Maintenance-free battery4 In cases where a “sealed-for-life”maintenance-free battery is fitted, topping-upand testing of the electrolyte in each cell is notpossible. The condition of the battery cantherefore only be tested using a batterycondition indicator or a voltmeter.5 If testing the battery using a voltmeter,connect the voltmeter across the battery andcompare the result with those given in theSpecifications under “charge condition”. Thetest is only accurate if the battery has notbeen subject to any kind of charge for theprevious six hours. If this is not the case,switch on the headlights for 30 seconds, thenwait four to five minutes before testing thebattery after switching off the headlights. Allother electrical components must be switchedoff, so check that the doors and tailgate arefully shut when making the test.6 If the voltage reading is less than 12.2 volts,then the battery is discharged, whilst areading of 12.2 to 12.4 volts indicates apartially discharged condition.7 If the battery is to be charged, first removeit from the vehicle.ChargingStandard and low maintenance battery8 Charge the battery at a rate of 3.5 to 4amps and continue to charge the battery atthis rate until no further rise in specific gravityis noted over a four hour period.9 Alternatively, a trickle charger charging at therate of 1.5 amps can be safely used overnight.10 Specially rapid “boost” charges which areclaimed to restore the power of the battery in1 to 2 hours are not recommended as theycan cause serious damage to the batteryplates through overheating.11 While charging the battery, note that thetemperature of the electrolyte should neverexceed 37.8ºC (100ºF).Maintenance-free battery12 This battery type takes considerablylonger to fully recharge than the standardtype, the time taken being dependent on theextent of discharge, but it can take anythingup to three days.13 A constant voltage type charger isrequired, to be set, when connected, to 13.9to 14.9 volts with a charger current below 25amps. Using this method the battery shouldbe useable within three hours, giving a voltagereading of 12.5 volts, but this is for a partiallydischarged battery and, as mentioned, fullcharging can take considerably longer.14 If the battery is to be charged from a fullydischarged state (condition reading less than12.2 volts) have it recharged by your Forddealer or local automotive electrician as thecharge rate is higher and constant supervisionduring charging is necessary.2.3 Battery securing clamp and bolt5