Chapter 1 Routine maintenance and servicing

Fuel system – carburettor engines 4A•1314 Prise free and remove the tamperproofseal, then unscrew and remove the idlemixture adjustment screw.15 Undo the retaining screws, and removethe throttle housing from the carburettor mainbody.Cleaning and inspection16 Wash the carburettor components,drillings and passages with clean petrol, thenblow them dry using a low-pressure air line. Ahigh-pressure air line must not be applied tothe accelerator pump discharge assembly orthe pump supply valve, as they each contain arubber Vernay valve, and these can easily bedamaged under high pressure. Never use apiece of wire for cleaning purposes.17 Examine all of the carburettorcomponents for signs of damage or wear,paying particular attention to the diaphragms,throttle spindle and plates, needle valve andmixture screw; the power valve jet is adjacentto the primary main jet. Renew alldiaphragms, sealing washers and gaskets asa matter of course.Reassembly18 Refit the throttle housing to thecarburettor main body (fitting a new gasket),and secure with its retaining screws.19 Refit the idle mixture adjustment screw.Make an initial adjustment by screwing it fullyin (but do not overtighten or screw it onto itsseat), then unscrew it two full turns.20 Where fitted, reassemble the throttlekicker, ensuring that its diaphragm lies flat,and that the relative position of the operatinglink to the kicker cover is correct.21 Fit the power valve, ensuring that itsdiaphragm lies flat and the vacuumgallery aligns with the diaphragm andhousing.22 Refit the accelerator pump. Take care notdamage the valve as it is inserted, and checkthat the O-ring seal is correctly located on theend of the valve. Check that the valve is nottrapped by the spring.23 Refit the accelerator pump discharge jet.Take care not to damage the valve and/or theO-ring seal, and ensure that they are correctlylocated.24 Commence reassembly of the upper bodyby inserting the emulsion tubes and the aircorrection jets into their respective ports (asnoted during removal).25 Screw the anti-dieseling solenoid intoposition. Ensure that the aluminium washer isfitted, and take care not to overtighten thevalve.26 Refit the needle valve and the float, andadjust the float setting as described in Section20.27 Refit the choke control mechanism, andsecure with its three retaining screws.28 Locate a new gasket onto the matingface, then refit the carburettor upper body tothe main body. As they are reassembled, takecare not to snag the float on the carburettormain body. Fit and tighten the retainingscrews to secure.29 On completion, refit the carburettor asdescribed in Section 23. Where applicable,check and adjust the throttle kicker setting(Section 21) after adjusting the idle speed andmixture settings.27 Throttle kicker unit (WeberDFTM carburettor) - removal,refitting and adjustment4Refer to the procedure contained in Section21.25 Carburettor (Weber DFTM) -descriptionThe carburettor operates in essentially thesame manner as TLDM instrument describedin Section 18, but the following featuresshould be noted.A throttle kicker is fitted to both manualtransmission, and CTX automatic transmissionmodels, the operation of the unit isdescribed in Section 18.The secondary venturi (barrel) is vacuumoperatedon manual transmission models. OnCTX automatic transmission equipped modelsit is operated sequentially.A bleed back solenoid (if fitted) is used tocontrol the amount of fuel being delivered tothe venturi by the action of the acceleratorpump.Idle speed and mixture adjustmentprocedures are described in Chapter 1, but itis important to note that accurate adjustmentscan only be made using the necessaryequipment.26 Carburettor (Weber DFTM) -fast-idle speed adjustment 4Refer to the procedure contained in Section19, but note the following points:a) When removing the air cleaner, do notdisconnect the vacuum supply orcrankcase ventilation hoses; the aircleaner should be positioned clear of thecarburettor assembly.b) The fast-idle adjusting screw is locatedon the side of the linkage (seeillustration).26.1 Manual choke fast-idle adjustment.Inset shows fast-idle adjusting screw(Weber DFTM carburettor)28 Carburettor (Weber DFTM) -removal and refitting4Note: Refer to the warning note in Section 1before proceeding. New gaskets will berequired on refitting, and a tachometer and anexhaust gas analyser will be required oncompletion.Removal1 Disconnect the battery negative (earth) lead(refer to Chapter 5A, Section 1).2 Remove the air cleaner as described inSection 2.3 Disconnect the choke cable from thecarburettor (Section 6).4 Carefully prise out the accelerator linkretaining clip, remove both securing bolts,then detach the cable and bracket assembly.Position the cable and bracket assembly clearof the carburettor.5 Disconnect the fuel feed hose at thecarburettor, and plug its end to avoid spillageand prevent dirt ingress. If a crimped typehose clip is fitted, cut this free taking care notto damage the hose.6 Disconnect all relevant vacuum pipes fromthe carburettor, having labelled them forsubsequent refitting.7 Disconnect the electrical lead from the antidieseling(fuel cut-off) solenoid, and the bleedback solenoid (if fitted).8 Remove the four nuts securing thecarburettor to the inlet manifold, thenwithdraw it from the vehicle.Refitting9 Clean the carburettor and manifold gasketmating faces.10 Refit in the reverse order of removal. Fit anew gasket, and tighten the retaining screwssecurely. Ensure that the fuel supplyhose connection to the carburettor issecurely fitted, using a new screw typeretaining clip.11 Reconnect the choke cable, and adjust itas described in Section 6.12 Refer to Section 2 and refit the aircleaner.13 When the battery is reconnected, startand warm up the engine then check the idlespeed and mixture settings as described inChapter 1.4A1595Ford Fiesta Remake