,6 Chapter 4 Ignition system
9 The spark plug gaf} is 01 conside rable impor1~e. as. if it is too lilrge or too small. the size of the spark ilnd its efficiency will be seriously impilired. The spilrk plug should be set to the ligure given in thl} Specifications ill the beginning of this Chapter; IOTa sel it, measure the gilp with a/cere, gauge. and then bend open. or close. the outer plug electrode untillhe correct gap is achieved. The centre electrode should never be benl as this may crack the insulation ilnd cause plug fAilure if nothing worse. 11 Relit the plugs, and re/ilthe leads from the distr ibu tor in the correct I"ing order. which is given in the Specifications. Screw the plugs in by hilnd initiilily then tighten them to the specified torque using the plug spilnnel.
12 Fault diagnosis -ignition system
By lar (he nlo1jori (y 01 brCJkdown and running troubles ilre caused by InUits In the igrlOlron system er(her in (he low (enSlon or high tens ion circuns There LJratlon or fuel Injec tion Setlln(Js, ilre normally tllle to faults in the d,strrllulOr Or 10 Incorrect I(Jrlltion tlllllrl!J .
Engine fails 10 staft 1 If the engine falls to StM( and t he cal was IIJnning norll1t1l1y when.t wns IJst used, first check ther e is fuel in the petrol wnk. If (he engille tums ovel normally on (he starter 1I10tor and the bilHery is evidently well chmged. then the lault mny be in either the high or low tension circuits. Firs( check Ihe HT circuit. Note: If lire hal/cry is known 10 hI! {(Illy ch,}lged, Ihe ignilion liglll cOllies on, ,1I)d Ihe s/arler 1II010r {,lils /() tum IIIe ongine check the tightness o f the le'lds on the biltlely terillinilis ,1I)d <1Iso (lte seCUIIHWSS oflhe e,l,th leold (0 irs cOllllec/ion 10 tire body It is qui(e common for tlie le,1(ls /0 Ii,}ve wOlked loose. l.'vc'1I If Ihey look ,1n(/ lecl seclI,e. /I one 01 the boll/my ((:{minM {Josts [11.'1.1' vC'IV liot wi".." (Iyiny (0 wOlk Ihe s/mler 1II0tOl (his is ;/ sUie IIId'C,7/IUI/ 0/ ;/ I;wlty COllllel;('On 1(1 1h.11Ie"lIillal. 2 One of tile commonest rOilsons lor bad stmtln!J IS wet or d;UllP sp,uk plug lead~ and dlstribu(or. Hemove (he distllblltor cap. H "JOdenSil(Ion is v iSIble IIlte!llillly dry the CJp With il rag and also wIpe ;lCf the leads nelu the cap_ 3 If (he enUiue sull fmls 1 0 St.l.t. check that cunent IS reachlllg (he JUS, by dlscounectln!1 ench plug le,l<1 in turn ilt the sp1Hk plllU end, .. ,ld holdlllg Ihe end olthe callie about 5 mm (0.2 Ill) aWilY from the cylillder block. Spin the enu'ne all the sta rter motor. 1 Spa,klllg between the end of the cable ilnd Ihe block should he fa"ly strong With J strong leuulm blue spark_ (Hold (he lead WI(h wbber to ilvold elec(IIc shocks) If Clluelll is reilching (he plugs. then rel110Ve them and clean and reg,lp them. Tho engine should now SWrt 5 If there is no spilrk ilt the plug leilds. wke of! the HT lead from the cenlre of the d'sltibutor C
6 If Ihere me no spmks Irom the end of the lend 110m the coil check the connections atlhe coil end of the lead. If il is in order 5(31 1 checking (he low tension circuit. 7 Use iI 12V voltmeler or a 12V bulb ilnd two leng(hs of w ire. On conventional distributors switch on the ignilion i1nd ensure tha t the points arc open. On breakerless dlstlibulOlS ensure thilt Ihe segments on the rOlor are nOt adJilcenl to (he triggel coil. Make a tes t between the low tension wire to the COil ( + ) terminal nnd eilrth. A leading of 7 (0 8 'lollS should be obtained. N o reJding indiCiites a break in the supply from the ignition swilCh or il f,1UIl in the ballast resiswnce wire. A correct rending indicn(es a faulty cojl or condensel, or n blok en lend between the coil ilnd the distrIbutor. On breokedess ignition systems the (rigger coil and ilmplificr module are suspect . H~ve (hem checked by a Ford dealer. . 8 Take the condenser wire off the points assembly Jnd with the points open test between the moving point ilnd eMth. If there is now a leildrng then the tault is in (he condenser. Fit a new one as dcsclibed in this Chapter, Section 5 9 W,th no reilding from the moving point to eilrth, wke ,1 reildrng between eil/th ,1nd the ell or negiltive ( - ) teminal ot (he COIl. A rendm(J here shows a broken wire which will need to be renewed hetween (he COil ilnd dis(rihutor. No retlding confirms thil1the coil hilS failed ilnd must be renewed, afler which the eno"te wdl run once more Rcmtmher (0 rel,t tho condenser wire 10 the pomt$ ilssemhly.
Engine misfires 10 If the enOlnr. mlsfues re!Julariy. run It ilt a f~st irllrng speed. Pull off eilch 01 the plu(! C,lpS III hUll nnd hsten t o (he note 01 the engrne. Hold the phl(J cnp In il dry cloth or with a rubber g love
other Pollt of the dlstllhu(or. These lilles J,e p,lths which now conduct electllcit y Jcross the CJp lhus lewng it run to e,,'th. Tile only answer IS a new distllbutor CilP_ 16 APilit frorn the Ignition tll1l1ng being Incorrect. other Ciluses of rlllsl,,,ng hilve already been denl( w l(h under Ihe section dealrng with the f,lriUre of Ihe enuine to star I. To reCi!p - these 0110 Ih,lt:
(,J) The cOllm.lV be {,lufly giving ,111 iniNmil/elll mislile (b) Thele limy he ,1 (/iJmiJged wile or loose cOrlflee/ioll in till! low (eflsion circuil (c) The condensel /II,lY I;e shOll circuiling (i{ filled) (d) There nwy be a meehanic,lllolUI! IiI Ihe dis/flbll/or (bfOken dliving spindle or eOlllac/bleaker spring. if filled)
17 If the ignition (iming is too far reto1lded, it should be noted thallhe engine will tend to overheat. and there will he a quite no(iceable drop in powel. If the engine is overheating and Ihe power is down, and Ihe ,oni(ion tim in!) is correct. then Ihe carburenor or fuel injection should be checked, i1S ,I is likely that this is where the Iilult lies.
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