Chapter 1 Routine maintenance and servicing

Fuel system – carburettor engines 4A•9as described in Section 16. The power valveassembly can also be removed in a similarfashion.5 Prise free the accelerator pump dischargetube, but take care not to damage it or thecarburettor body.6 Remove the jets and emulsion tubes asrequired, making careful notes of theirrespective locations for reassembly.Cleaning and inspection7 Soak out the fuel in the float chamber usinga clean rag; this must be safely disposed of.Clean the float chamber, jets, drillings andpassages with clean petrol. The careful use ofan air line (or footpump) is ideal to blow outthe upper and lower bodies. Never use apiece of wire for cleaning purposes.8 Examine all of the carburettor componentsfor signs of damage or wear, paying particularattention to the diaphragms, throttle spindleand plates, and needle valve. Renew alldiaphragms, sealing washers and gaskets asa matter of course.Reassembly9 Refit the emulsion tubes and jets to theirlocations as noted during dismantling.10 Refit the accelerator pump dischargetube.11 Refit the accelerator pump and powervalve assemblies as described in Section 16.12 Refit the needle valve and the float, andadjust the float setting as described in Section14.13 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.14 On completion, refit the carburettor asdescribed in Section 15.18 Carburettor (Weber TLDM) -descriptionThe carburettor is of twin venturi,downdraught type, featuring a fixed size mainjet system, adjustable idle system, amechanically-operated accelerator pump, anda vacuum-operated power valve. A manuallyoperatedcold start choke is fitted, and athrottle kicker is used on certain models.In order to comply with emission controlregulations and maintain good fuelconsumption, the main jets are calibrated tosuit the 1/4 to 3/4 throttle range. The powervalve is therefore only used to supplyadditional fuel during full-throttle conditions.The accelerator pump is fitted to ensure asmooth transmission from the idle circuit tothe main jet system. As the accelerator pedalis depressed, a linkage moves the diaphragmwithin the accelerator pump, and a smallquantity of fuel is injected into the venturi, toprevent a momentary weak mixture andresultant engine hesitation.The manually-operated choke features avacuum-operated pull-down mechanismwhich controls the single choke plate undercertain vacuum conditions.On CTX automatic transmission models,the throttle kicker acts as an idle speedcompensator for when the transmission shiftlever positions R, D or L are selected. Thethrottle kicker is operated by vacuum suppliedfrom the inlet manifold. When the appropriatetransmission shift lever position is selected,the throttle kicker control solenoid allows thevacuum to pass to the throttle kicker whichmaintains the idle speed by means of adiaphragm and mechanical linkage.On manual transmission models, thethrottle kicker (when fitted) acts as a damperby slowing down the closing action of thethrottle plate. Under deceleration, thismaintains the combustion of the air/fuelmixture entering the cylinders, thus improvingthe exhaust emission levels. A vacuumsustain valve controls the carburettor-sourcedvacuum applied to the throttle kicker unit; thisallows the vacuum slowly to decay, allowingnormal engine idling speed to be achieved.An anti-dieseling (fuel cut-off) solenoid isfitted to prevent the possibility of the enginerunning on after the ignition is switched off.Idle speed and mixture adjustmentprocedures are described in Chapter 1, but itis important to note that accurate adjustmentscan only be made using the necessaryequipment.19 Carburettor (Weber TLDM) -fast-idle speed adjustment 4Note: Before carrying out any carburettoradjustments, ensure that the spark plug gapsare set as specified, and that all electrical andvacuum connections are secure. To carry outchecks and adjustments, an accuratetachometer and an exhaust gas analyser (COmeter) will be required.1 Check the idle speed and mixture settings19.4 Fast-idle speed adjusting screw(arrowed) (Weber TLDM carburettor)are as specified (as described in Chapter 1).These must be correct beforechecking/adjusting the fast-idle speed.2 With the engine at its normal operatingtemperature, and a tachometer connected inaccordance with the manufacturer’sinstructions, switch the engine off, thenremove the air cleaner (if not already done) asdescribed in Section 2.3 Actuate the choke by pulling the controlknob fully out, then start the engine and notethe engine fast-idle speed. Compare it withthe specified speed.4 If adjustment is required, turn the fast-idleadjusting screw clockwise to decrease, oranti-clockwise to increase, the fast-idle speed(see illustration).5 Recheck the fast-idle and basic idlespeeds.6 On completion of the adjustment, stop theengine, detach the tachometer and CO meter,reconnect the radiator cooling fan lead, andrefit the air cleaner.20 Needle valve and float (WeberTLDM carburettor) - removal, 4refitting and adjustmentNote: Refer to the warning note in Section 1before proceeding. New gaskets and a washer(seal) will be required when reassembling. Atachometer and an exhaust gas analyser (COmeter) will also be required to check theidle speed and mixture settings oncompletion.Removal and refitting1 Disconnect the battery negative (earth) lead(refer to Chapter 5A, Section 1).2 Remove the air cleaner as described inSection 2.3 Clean the exterior of the carburettor, thendisconnect the fuel supply hose and the antidieselingsolenoid wiring.4 Disconnect the choke control cable.5 Undo and remove the six retaining screws(four of which are Torx type) and carefully liftthe carburettor upper body clear (seeillustrations).6 Invert and support the upper body of thecarburettor for access to the float and pivot.20.5a Remove the carburettor upper bodysecuring screws . . .4A1595Ford Fiesta Remake