Chapter 1 Routine maintenance and servicing

Fuel system – carburettor engines 4A•1516 Prise out the tamperproof seal coveringthe fuel mixture screw, then undo and removethe mixture screw.Cleaning and inspection17 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.18 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.Reassembly19 Refit the fuel mixture screw by fullywinding the screw in, then unwinding threeturns to give an approximate setting.20 Refit the power valve assembly ensuringthat the diaphragm lies flat, and that thevacuum gallery lines up correctly with thediaphragm and housing.21 Reassemble the secondary barreldiaphragm into its housing, ensuring thatthe diaphragm lies flat and that the vacuumgallery lines up with the diaphragm andhousing. Also, to assist with installation, donot reconnect its operating rod until the coverhas been secured.22 Refit the throttle kicker mounting bracket.23 Refit the anti-dieseling (fuel cut-off)solenoid, using a new sealing washer.24 Refit the accelerator pump assembly,ensuring that the diaphragm lies flat and is notkinked.25 Reassemble the throttle kicker, ensuringthat the diaphragm lies flat and that therelative position of the diaphragm operatinglink to the throttle kicker cover is correct. Fullyattach the throttle kicker assembly.26 Refit the main and idle jets, makingreference to the notes taken duringdismantling to ensure correct fitted locations.27 Reassemble the carburettor upper bodyas described in the following paragraphs.28 Refit the needle valve housing (using anew washer if applicable).29 Refit the needle valve and float assembly,having ensured that the float tag locatesbelow the spring clip on the needle valve.Insert the float retaining pin to secure.30 Adjust the float level as follows. Ensuringthat a new gasket is fitted to the carburettorupper body, hold the upper body in thevertical position; the needle valve must beshut off. Measure the distance shown (seeillustration), and adjust by bending the floattag if the measurement is outside thespecification. Recheck the float leveladjustment after bending the float tag, asnecessary.31 Refit the choke pull-down diaphragm,ensuring that the diaphragm lies flat and thatthe vacuum gallery lines up correctly with thediaphragm and housing (see illustration).32 Adjust the choke pull-down as follows.Fully close the choke, then manually push thediaphragm operating rod up to its stop;measure the distance between thedowndraught side of the choke plate and theventuri, using a gauge rod or the shank of atwist drill bit (of known size). If themeasurement is outside specification, removethe tamperproof seal from the housing, andadjust the now revealed adjustment screwaccordingly. Fit a new tamperproof seal aftersuccessful adjustment.33 Refit the fuel feed filter, and secure withits brass nut and sealing washer.34 Refit the carburettor upper body to thecarburettor main body, ensuring that its newgasket seats correctly and that the float doesnot foul during assembly. Insert and tightenthe securing screws.35 Reconnect any vacuum pipes removedduring dismantling (where applicable).36 On completion, refit the carburettor asdescribed in Section 28. Where applicable,check and adjust the throttle kicker setting(Section 27) after adjusting the idle speed andmixture settings.30 Carburettor (Weber TLD) -descriptionThis carburettor incorporates many of thefeatures of the TLDM type described inSection 18. The main differences are that athrottle kicker is not used, the secondaryventuri (barrel) is vacuum-operated, and that acoolant-heated automatic choke controlsystem is fitted.The choke system is fully automatic. Whenthe engine is cold, the bi-metal spring whichcontrols the position of the choke plate is fullywound up, and holds the plate closed. As theengine warms up, the bi-metal spring isheated by the coolant and begins to unwind,thereby progressively opening the chokeplate. A vacuum-operated pull-downmechanism controls the choke plate undercertain operating conditions, and an internalfast-idle system is incorporated.Idle speed and mixture adjustmentprocedures are described in Chapter 1, but itis important to note that accurate adjustmentscan only be made using the necessaryequipment.31 Carburettor (Weber TLD) -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 accurate4A29.30 Float level adjustment (Weber DFTMcarburettor)A Float level setting dimensionB Adjusting tag29.31 Exploded view of the choke pull-down assembly (Weber DFTM carburettor)A Housing B Diaphragm1595Ford Fiesta Remake