Carburetor - Aisan 2-bbl Toyota Tercel L20

DESCRIPTION

Carburetor is a 2-barrel, downdraft design, equipped with an automatic choke consisting of a bi-metallic coil and an electrically-operated ceramic heater. A piston type accelerator pump is incorporated into the primary barrel and an auxiliary accelerator pump system (AAP), aids in cold engine acceleration.

Other features include diaphragms which open secondaries at high speed and full throttle operation, throttle positioner, choke opener, choke breaker, deceleration fuel cut, and hot idle compensation devices.

CARBURETOR IDENTIFICATION

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article, see TUNE-UP article in TUNE-UP section.

Note. Manufacturer recommends using Carburetor Service Kit 09860-11011 to make carburetor adjustments and measurements on Corolla models; Kits 09240-00014 and 09240-00020 for Tercel models.

FLOAT LEVEL

Note. Remove needle valve wire clip and install new inlet seat gasket before adjusting float.

Remove air horn gasket, invert air horn and allow float to hang by its own weight. Measure clearance between top of float and air horn. (Scheme 27) Clearance should be.283" (7.2 mm). Adjust clearance by bending float arm at tab "A". (Scheme 28)

Float Level Measurement. Scheme 27

Float Level Adjustment Adjust gap by bending float arm at tab "A". Scheme 28

FLOAT DROP

1. Invert air horn, gently lift up float and measure clearance between needle valve and float arm. (Scheme 29) Clearance should be.066-.078" (1.67-1.99 mm).
2. Adjust clearance by bending outer float tab "B". (Scheme 30) Install needle valve clip after completing float adjustments.

Float Drop Measurement. Scheme 29

Float Drop Adjustment Bend outer tab "B" to adjust. Scheme 30

PRIMARY & SECONDARY THROTTLE VALVES

Invert carburetor, insert angle gauge and separately measure angle of primary and secondary throttle valves at full throttle. Primary throttle valve angle should be 90° from horizontal plane for all models. Secondary throttle valve angle should be 75° for Corolla RWD models and all Tercel models; 80° for Corolla FWD models. Adjust by bending the respective throttle lever stop.

Bench Adjustment

Position throttle shaft lever to high (first) step of fast idle cam. Close choke valve and measure primary throttle valve angle. Angle should be 20°. Adjust by turning fast idle adjustment screw.

CHOKE UNLOADER

Fully open primary throttle valve, insert angle gauge and measure choke valve angle. Angle should be 41°. Bend fast idle lever to adjust. (Scheme 31)

Choke Unloader Adjustment Bend fast idle lever to adjust. Scheme 31

CHOKE OPENER

1. Set fast idle cam, open throttle slightly and gently push choke valve closed. Keeping choke valve closed, release throttle valve.
2. Apply vacuum to choke opener diaphragm and measure choke valve angle. Angle should be 77°. Adjust by bending tang on relief lever, connecting choke opener link to choke valve shaft.

Scheme 32

1. Fully close choke valve. Apply vacuum to choke breaker inner diaphragm "A". Measure choke valve angle. Angle should be 38°. (Scheme 32) (Scheme 32): Choke Breaker Adjustment
2. Adjust by bending tang on relief lever, connecting breaker diaphragm link to choke valve shaft.
3. Apply vacuum to both choke breaker diaphragms "A" and "B". Measure choke valve angle. Angle should be 55° for Corolla models and 52° for Tercel models. Adjust by turning diaphragm adjustment screw.

SECONDARY KICK-UP

Fully open primary throttle valve. Measure clearance between secondary throttle valve and the body. Clearance should be.0043-.0087" (.11-.22 mm). Adjust by bending secondary throttle lever. (Scheme 33)

Secondary Kick-Up Adjustment. Scheme 33

SECONDARY TOUCH ANGLE

Check primary throttle valve opening angle as the primary kick lever touches the secondary kick lever. Angle should be 45°. Adjust by bending primary kick lever. (Scheme 34)

Secondary Touch Angle Adjustment. Scheme 34

ACCELERATOR PUMP STROKE

Place a straightedge on top of air horn. Fully open choke valve and measure full travel of pump plunger. Plunger travel should be.157" (4.0 mm). Adjust pump stroke by bending linkage rod at existing bend. (Scheme 35)

Accelerator Pump Stroke Adjustment Bend linkage rod at existing bend to adjust. Scheme 35

OVERHAUL

Note. Manufacturer recommends using Carburetor Driver Kit 09860-11011 to service carburetor.

Air Horn

1. Disconnect choke link and accelerator pump connecting rod. Remove pump arm pivot screw and pump arm. Disconnect choke breaker vacuum hose. Remove fuel line and union and 8 air horn screws.
2. Disconnect the choke opener link and remove air horn with gasket from body. Disconnect wiring and remove primary and secondary solenoid valves from body.
3. Remove float pivot pin, float and needle valve assembly. Remove air horn gasket, needle valve seat and gasket, power piston retainer, power piston and spring. Remove pump plunger and boot. (Scheme 36)

Exploded View of Air Horn Assembly. Scheme 36

Main Body

1. Disconnect throttle positioner links and remove bracket attaching bolts. Remove accelerator pump retainer gasket and remove pump discharge weight, long spring and discharge large ball. (Scheme 38)
2. Remove pump dampening spring and using tweezers, remove retainer and check ball. Remove slow jet, power valve with jet and throttle positioner levers. Remove primary and secondary main passage plugs, primary main jets and gaskets.
3. Remove AAP housing, diaphragm and spring. Remove AAP inlet plug and check ball. Remove outlet plug, short spring and small ball. Remove primary and secondary small venturies.
4. Remove sight glass retainer, sight glass and "O" ring. Remove throttle lever return spring and back spring. Remove the throttle lever and fast idle cam.
5. Disconnect link, and remove secondary throttle valve diaphragm assembly and gasket. Remove the 3 body-to-flange bolts and vacuum passage bolt. Separate body from flange. (Scheme 37)

Exploded View of Carburetor Flange. Scheme 37

CLEANING

Note. Do not immerse synthetic parts, electrical components or diaphragm assemblies in carburetor cleaner.

Remove carbon from around throttle valve and clean cast parts with carburetor cleaner. Clean jets, fuel passages and vacuum ports with compressed air. Do not use wire or similar metal objects. Clean all other parts with solvent and soft brush.

Choke Heater

Measure resistance between inner half of thermostat housing and wire connector. Resistance at 68°F (20°C) should be 17-19 ohms for Corolla models; 20-22 ohms for Tercel models. Replace air horn, if resistance is not within specifications.

Float Assembly

Inspect pivot pin for scratches and excessive wear; float for pivot pin hole wear and broken lips; plunger spring for breaks and distortion; needle valve and plunger for wear or damage and seat strainer for rust or breaks.

Fuel Cut Solenoid Valves

1. Feel solenoid valve "click", as solenoid is connected and disconnected from battery. Test primary solenoid by connecting both lead wires to positive battery terminals.
2. Test secondary solenoid by connecting solenoid lead wire to battery terminal positive terminal and jumping solenoid body to negative battery terminal. Replace solenoid if it fails to operate properly.

REASSEMBLY

Reassemble by reversing the disassembly procedure, using new gaskets and "O" rings, as follows

1. When assembling flange parts, ensure vacuum passage bolt is installed in correct position. Ensure springs are installed in proper location and check balls are located in appropriate orifices.
2. When installing pump discharge weight and outlet valve assembly, ensure all components are installed in correct order. After installing power piston, check piston for smooth operation.
3. If choke valve has been separated from shaft, make certain to peen the new retaining screws after valve is installed on shaft. When installing air horn, tighten air horn screws gradually and alternately to prevent distortion.

Exploded View of Carburetor Main Body. Scheme 38

ADJUSTMENT SPECIFICATIONS

CARBURETOR ADJUSTMENT SPECIFICATIONS