Chapter 1 Routine maintenance and servicing

Every 20 000 miles or two years 1•19Every 20 000 miles (32 000 km) or two years, whichevercomes first21 Spark plug renewal and HTcomponent check 1Note: Spark plug renewal at this serviceinterval is only necessary on the HCS, CVHand PTE engines. On Zetec engines, therecommended interval for spark plug renewalis every 30 000 miles or three years.Spark plug check and renewal1 It is vital for the correct running, fullperformance and proper economy of the enginethat the spark plugs perform with maximumefficiency. The most important factor in ensuringthis is that the plugs fitted are appropriate for theengine. The suitable type is given in theSpecifications Section at the beginning of thisChapter, on the Vehicle Emissions ControlInformation (VECI) label located on theunderside of the bonnet (only on models sold insome areas) or in the vehicle’s Owner’sHandbook. If the correct type is used and theengine is in good condition, the spark plugsshould not need attention between scheduledrenewal intervals. Spark plug cleaning is rarelynecessary, and should not be attempted unlessspecialised equipment is available, as damagecan easily be caused to the firing ends.2 Spark plug removal and refitting requires aspark plug socket, with an extension which canbe turned by a ratchet handle or similar. Thissocket is lined with a rubber sleeve, to protectthe porcelain insulator of the spark plug, and tohold the plug while you insert it into the sparkplug hole. You will also need a set of feelergauges, to check the spark plug electrode gap,and a torque wrench to tighten the new plugsto the specified torque (see illustration).3 To remove the spark plugs, first open thebonnet; the plugs are easily reached at thetop of the engine. Note how the spark plug(HT) leads are routed and secured by clips,and on some engines, how they’re positionedalong the channel in the cylinder head cover.To prevent the possibility of mixing up sparkplug (HT) leads, it is a good idea to try to workon one spark plug at a time.4 If the marks on the original-equipment sparkplug (HT) leads cannot be seen, mark the leads1 to 4, to correspond to the cylinder the leadserves (No 1 cylinder is at the timing belt/chainend of the engine). Pull the leads from the plugsby gripping the rubber boot, not the lead,otherwise the lead connection may be fractured.5 It is advisable to soak up any liquid in thespark plug recesses with a rag, and to removeany dirt from them using a clean brush,vacuum cleaner or compressed air beforeremoving the plugs, to prevent any dirt orwater from dropping into the cylinders.Warning: Wear eye protectionwhen using compressed air!6 Unscrew the spark plugs, ensuring that thesocket is kept in alignment with each plug - ifthe socket is forcibly moved to either side, theporcelain top of the plug may be broken off. Ifany undue difficulty is encountered whenunscrewing any of the spark plugs, carefullycheck the cylinder head threads and taperedsealing surfaces for signs of wear, excessivecorrosion or damage; if any of theseconditions is found, seek the advice of a Forddealer as to the best method of repair.7 As each plug is removed, examine it asfollows - this will give a good indication of thecondition of the engine. If the insulator nose iscovered with light tan to greyish-browndeposits, then the mixture is correct, and it islikely that the engine is in good condition.8 If the tip and insulator nose are coveredwith hard black-looking deposits, then this isindicative that the mixture is too rich. Shouldthe plug be black and oily, then it is likely thatthe engine is fairly worn, as well as the mixturebeing too rich.9 If the insulator nose of the spark plug is21.2 Tools required for changing sparkplugs21.12b Spark plug manufacturersrecommend using a wire-type gauge whenchecking the gap - if the wire or feeler gaugedoes not slide between the electrodes with aslight drag, adjustment is requiredclean and white, with no deposits, this isindicative of a weak mixture.10 If you are renewing the spark plugs,purchase the new plugs, then check each ofthem first for faults such as cracked insulatorsor damaged threads. Note also that,whenever the spark plugs are renewed as aroutine service operation, the spark plug (HT)leads should be checked as described below.11 The spark plug electrode gap is ofconsiderable importance as, if it is too large ortoo small, the size of the spark and itsefficiency will be seriously impaired. The gapshould be set to the value given in theSpecifications Section of this Chapter. Newplugs will not necessarily be set to the correctgap, so they should always be checkedbefore fitting.12 The spark plug gap is correct when thecorrect-size feeler gauge or wire gauge is afirm sliding fit between the electrodes (seeillustrations).13 To adjust the electrode gap, bend open, orclose up, the outer plug electrode until thecorrect gap is achieved (see illustration). Thecentre electrode should never be bent, as thismay crack the insulation and cause plug failure,21.12a Measuring a spark plug gap with afeeler gauge21.13 To change the gap, bend the outerelectrode only, and be very careful not tocrack or chip the porcelain insulatorsurrounding the centre electrode11595Ford Fiesta Remake