Kohler KDW 2204 - Hydraulic Tappet Operation; Injection Pump Follower

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Hydraulic tappet operation
The operatingprinciple of thehydraulic tappet isbased on the
incompressibilityoftheliquidsandoncontrolledleakage.
Through pushrod 1, the pressurised oil gets into thetappet in
chamberA(low-pressurechamber),maintainingaconstantowof
oilintheabovechamberaswellasinthehigh-pressurechamberB.
TheoilcanonlyenterchamberBthroughthenon-returnvalve2
andleavethroughtheclearancebetweentheplunger3andthe
tappetbody4(controlledleakage).
ChamberB isrelledwhenthetappetisonthebottomofthecam
baseandspring5 keepsplunger3 pressed,thuseliminatingthe
clearance in the entire valve-rocker arm-push rod-tappet-cam
system.
Thetappetbodymovesawayfromtheplungercreatingaslight
vacuuminchamberB andcausingthevalve2 toopen,thusallowing
theoilinchamberA toowintochamberB,re-establishingthe
quantityofoilrequiredforoptimalrunningconditions.
Difcultoperatingconditions:
Forcorrectfunctioningofthehydraulictappetsthepressurechamberofplunger 3mustalwaysbelledwithoil.
However,thisisnotpossibleinsomeconditionsinthat,whentheengineisnotrunning,oilleakagesmaycausepartialemptying
ofthetappets.Thissituationwillcauseexcessiveclearancewhichwillmakeitselfapparentthroughanunusualtickingsoundthat
isnottobeconfusedwiththenormaltickingoftheinjectors.
1 -Startingfromcold:theenginehasnotbeenusedforsometimeandoilmayhaveleakedoutofthepressurechamberofthe
tappets.Moreover,lubricantowswithgreaterdifcultyatlowtemperatures,andhenceseveralsecondsmaygobybefore
thetappetsareonceagainsuppliedwithoil.
2 - Engine very hot: at minimum speed, the oil pressure is low and tiny air bubbles may form inside it (more than 5% of its
volume).Thiscausesthelubricanttobecomecompressibleandthetappetissqueezedslightlycreatingclearanceand,
thusmakinganoise.
3 - Startingandstoppingtheenginerepeatedly(veryrare):inthissituationthetappetsmayemptytemporarily.
4 - Anoilwithaviscositynotadequatetotheenvironmentalconditionsoftheenginemayaffecttheproperfunctioningofthe
hydraulictappets.
Forthedeterminationoftheadequateviscosityofoilreferredtopage.29.
Inallfourcasesthetickingshouldnotlasttoolong.Ifthisisnotthecase,theproblemisdenitelyduetoamanufacturingfault,
wearandtearordirt,whichcanbedrawninbytheoilandgetbetweenthenon-returnvalveanditsseatinsidetheplunger,thus
compromisingthefunctioningofthetappets.Inthiscasethehydraulictappetsmustbereplaced.
Injection pump follower
Introducethefollowerintoitshousingandmanuallyturnscrew3
untilitmatcheswithnotch2.
Beforelockingscrew3useyourngertocheckthatthefollower
isallowedtomoveupwardsfreely.
Space 1 should be introduced into the pushrod with the at
surfacefacingupwards
Note: The screws 3a can be tted without distinction in each
cylinder.
 Screw3b however,whichisshorterthantheothers,has
to be ttedon thetiming sideof thecylinder (insidethe
stoplevercover).
Workshop Manual KDW 1603_2204_2204/T _ cod. ED0053029180 - 1° ed_rev. 00