Toyota Pick-ups/Land Cruiser/4Runner 1970-1988

Carburetor

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See Figures 1, 2, 3, 4 and 5

The carburetor is the most complex part of the fuel system. Carburetors vary greatly in construction, but they all operate basically the same way; their job is to supply the correct mixture of fuel and air to the engine in response to varying conditions.

Despite their complexity in operation, carburetors function because of a simple physical principle (the venturi principle). Air is drawn into the engine by the pumping action of the pistons. As the air enters the top of the carburetor, it passes through a venturi, which is nothing more than a restriction in the throttle bore. The air speeds up as it passes through the venturi, causing a slight drop in pressure. This pressure drop pulls fuel from the float bowl through a nozzle into the throttle bore, where it mixes with the air and forms a fine mist, which is distributed to the cylinders through the intake manifold.

There are six different systems (air/fuel circuits) in a carburetor that make it work; the Float system, Main Metering system, Idle and Low-Speed system, Accelerator Pump system, Power system, and the Choke system. The way these systems are arranged in the carburetor determines the carburetor's size and shape.

It's hard to believe that the 2 bbl carburetor used on 4 cylinder engines have all the same basic systems as the enormous 4 bbl carburetors used on V8 engines. Of course, the 4 bbls have more throttle bores ("barrels") and a lot of other hardware you won't find on the little 2 bbls. But basically, all carburetors are similar, and if you understand a simple 2 bbl, you can use that knowledge to understand a 4 bbl. If you'll study the explanations of the various systems on this stage, you'll discover that carburetors aren't as tricky as you thought they were. In fact, they're fairly simple, considering the job they have to do.

It's important to remember that carburetors seldom give trouble during normal operation. Other than changing the fuel and air filters and making sure the idle speed and mixture are OK at every tune-up, there's not much maintenance you can perform on the average carburetor.

The carburetors used on Toyota models are conventional 2 bbl, downdraft types similar to domestic carburetors. The main circuits are: primary, for normal operational requirements; secondary, to supply high speed fuel needs; float, to supply fuel to the primary and secondary circuits; accelerator, to supply fuel for quick and safe acceleration; choke, for reliable starting in cold weather; and power valve, for fuel economy. Although slight differences in appearance may be noted, these carburetors are basically alike. Of course, different jets and settings are demanded by the different engines to which they are fitted.



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Fig. Fig. 1: Exploded view of the carburetor-18R-C engine



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Fig. Fig. 2: Exploded view of the carburetor-18R-C engine



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Fig. Fig. 3: Exploded view of the carburetor-20R engine



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Fig. Fig. 4: Exploded view of the carburetor-20R engine



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Fig. Fig. 5: Exploded view of the carburetor-22R engine

REMOVAL & INSTALLATION



See Figures 6 through 21

  1. Disconnect the negative battery cable.
  2.  
  3. Loosen the radiator drain plug and drain the coolant into a suitable container.
  4.  
  5. Unscrew the mounting screws and remove the air filter housing. Disconnect all hoses and lines leading from the air cleaner.
  6.  
  7. Tag and disconnect all fuel, vacuum, coolant and electrical lines or hoses leading from the carburetor.
  8.  
  9. Disconnect the accelerator linkage from the carburetor. On cars equipped with an automatic transmission, disconnect the throttle cable linkage running from the transmission.
  10.  
  11. Remove the four carburetor mounting bolts and lift off the carburetor and its gasket.
  12.  

Cover the manifold opening with a clean rag to prevent anything from falling into the engine.

  1. Install the carburetor (with a new gasket), tighten the mounting bolts EVENLY in steps and reconnect all linkage.
  2.  
  3. Start the engine and check for any leaks. Check the float level.
  4.  



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Fig. Fig. 6: Removing the fuel line from the carburetor



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Fig. Fig. 7: Side view of the carburetor



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Fig. Fig. 8: Mark all hoses for correct installation before removing the carburetor



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Fig. Fig. 9: Removing the carburetor front mounting bolts



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Fig. Fig. 10: Removing the carburetor back mounting bolts



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Fig. Fig. 11: Removing the carburetor front mounting bolts



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Fig. Fig. 12: View of the carburetor front mounting bolts



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Fig. Fig. 13: Removing all external brackets for carburetor removal



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Fig. Fig. 14: Removing the carburetor assembly



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Fig. Fig. 15: Removing the carburetor mounting gasket (insulator)



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Fig. Fig. 16: Clean the carburetor mounting gasket (insulator) before installing the carburetor



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Fig. Fig. 17: Adjust the idle speed after installing the carburetor



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Fig. Fig. 18: Removing the pin for gas pedal linkage



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Fig. Fig. 19: Removing the housing for gas pedal linkage



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Fig. Fig. 20: Removing the clip for gas pedal linkage



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Fig. Fig. 21: Removing the wheel assembly pin for gas pedal linkage

ADJUSTMENTS



Float Level Adjustment
EXCEPT F AND 2F ENGINES

See Figures 22 and 23

Float level adjustments are unnecessary on models equipped with a carburetor sight glass, if the fuel level falls within the lines when the engine is running.

There are two float level adjustments which may be made on Toyota carburetors. One is with the air horn inverted, so that the float is in a fully raised position; the other is with the air horn in an upright position, so that the float falls to the bottom of its travel.

The float level is either measured with a special carburetor float level gauge, which comes with a rebuilding kit, or with a standard wire gauge.

  1. Turn the air horn upside down and let the float hang down by its own weight.
  2.  
  3. Using a special float gauge (available at your local dealer), check the clearance between the tip of the float and the flat surface of the air horn. The clearance should be:

    8R-C: 9.4mm
     
    18R-C: 5.0mm
     
    20R:
     
    1975-77 - 5.0mm
     
    1978-80 - 7.0mm
     
    22R:
     

  4.  



1981 - 9.8mm
 
1982 - 10.5mm
 
1982-88 - 9.8mm
 

This measurement should be made without the gasket on the air horn.

  1. If the float clearance is not within specifications, adjust it by bending the upper (center) float tab.
  2.  
  3. Lift up the float and check the clearance between the needle valve plunger and the float lip. Clearance on the 8R-C and 18R-C engines may be checked with a special float gauge or with a standard wire feeler gauge. 20R and 22R engines must only use the special float gauge. The clearance should be 48mm on all engines.
  4.  
  5. If the clearance is not within specifications, adjust it by bending the lower float tabs (2).
  6.  



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Fig. Fig. 22: Bend tab A to adjust the float in the rasied position-22R engine



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Fig. Fig. 23: Bend tab B to adjust the float in the lowered position-22R engine

F AND 2F ENGINES
  1. Remove the carburetor air horn. Invert the air horn and allow the float to hang towards the air horn.
  2.  
  3. With the air horn gasket removed, measure the distance between the float and the air horn, at the end of the float opposite the needle valve. The distance should be 7.5mm. If adjustment is necessary, remove the float and bend the tab which is centered between the hinge pivot points. After the adjustment is completed, reinstall the float and recheck the setting.
  4.  
  5. Lift upward on the float and measure the distance between the needle valve push pin and the lip of the float. The distance should be 1.1mm. If adjustment is necessary, remove the float and bend the tabs located just inside of the hinge points. After the adjustment is completed, reinstall the float and recheck the setting.
  6.  

Fast Idle Adjustment-Carburetor Off Truck
8R-C AND 18R-C

With the carburetor inverted and the choke fully closed, measure the distance from the primary throttle plate to the throttle bore using a wire gauge. It should measure 0.74mm on 8R-C carburetors, 1.0mm on 18R-Cs. Adjust the clearance to specifications by turning the fast idle adjustment screw.

1975-79 20R, F AND 2F ENGINES
  1. Remove the carburetor as previously outlined.
  2.  
  3. Close the choke valve completely and invert the carburetor.
  4.  
  5. Using a wire type feeler gauge, check the clearance between the upper half of the primary throttle blade and the throttle bore. The clearance should be 0.047 for 20R engines; 0.051 for F and 2F engines. If necessary, adjust the clearance by turning the fast idle screw.
  6.  
  7. Install the carburetor as previously outlined.
  8.  

1980 20R AND 1981-88 22R ENGINES

See Figure 24

A special blade angle tool must be obtained to properly make this adjustment.

  1. Remove the carburetor as previously outlined.
  2.  
  3. Close the choke valve completely and set the throttle shaft lever to the first seep of the fast idle cam.
  4.  
  5. Attach the blade angle tool to the primary throttle blade. Adjust the primary throttle blade angle to 23° from horizontal by turning the fast idle screw.
  6.  
  7. Remove the angle tool from the carburetor and install the carburetor as previously outlined.
  8.  



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Fig. Fig. 24: Fast idle adjustment with the carburetor off the vehicle-22R engine

Fast Idle Adjustment-Carburetor On Truck
1975-79 20R ENGINE
  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Stop the engine and disconnect the vacuum hose from the EGR valve. Connect a tachometer to the engine as previously outlined.
  4.  
  5. Open the throttle valve slightly and close the choke plate, which will set the fast idle cam.
  6.  
  7. Disconnect the vacuum hose(s) from the distributor vacuum unit. Plug the vacuum hose end(s).
  8.  
  9. Without touching the accelerator pedal, start the engine and read the tachometer. If necessary, adjust the fast idle speed to 2400 rpm by turning the fast idle screw.
  10.  
  11. Reconnect the vacuum hoses to both the EGR valve and the distributor vacuum unit. Disconnect the tachometer from the engine.
  12.  

1980 20R AND 1981-88 22R ENGINES
  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Stop the engine and connect a tachometer to the engine as previously outlined.
  4.  
  5. Remove the air cleaner assembly.
  6.  
  7. Disconnect the vacuum hose at the fast idle cam breaker (if so equipped) and plug the hose end.
  8.  
  9. Disconnect the vacuum hose(s) from the distributor vacuum unit.
  10.  
  11. Disconnect the vacuum hose from the EGR valve.
  12.  
  13. Open the throttle valve slightly and fully pull up on the fast idle linkage. Release the throttle.
  14.  
  15. Without touching the accelerator pedal, start the engine and read the tachometer. If necessary, adjust the fast idle speed by turning the fast idle screw. 20R and 1981-83 22R: 2400 rpm; 1984-86: 2600 rpm; 1987-88: 3000 rpm.
  16.  
  17. Reconnect the vacuum hoses, disconnect the tachometer and reinstall the air cleaner.
  18.  

F AND 2F ENGINES
  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Stop the engine and connect a tachometer to the engine as previously outlined.
  4.  
  5. Remove the air cleaner assembly.
  6.  
  7. Disconnect the vacuum hoses from both the EGR valve and the distributor vacuum unit.
  8.  
  9. Pull the dash mounted choke control knob fully outward.
  10.  
  11. Open the choke plate and prevent it from closing using a screwdriver. Do not jam the screwdriver into place.
  12.  
  13. Start the engine and read the tachometer. If necessary, adjust the fast idle speed to 1800 rpm by turning the fast idle screw.
  14.  
  15. Remove the screwdriver from the choke. Disconnect the tachometer and reconnect the vacuum hoses.
  16.  
  17. Install the air cleaner assembly.
  18.  

Unloader Adjustment

See Figure 25

The unloader adjustment is made with the primary throttle valve fully open. With the valve open, check the choke valve angle with a special gauge supplied in the rebuilding kit or with a gauge of the proper angle fabricated out of cardboard. The angle of the choke valve opening should be:



8R-C: 51°
 
18R-C: 47°
 
20R: 50°
 
22R: 45° (50° for 1983)
 

All angles, should be measured from the horizontal plane created by a closed choke valve.

To adjust the angle, bend the fast idle lever until the proper measurement is achieved.



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Fig. Fig. 25: Checking the choke valve opening angle

ON VEHICLE-1975-88

Disconnect the EGR valve vacuum line on 20R engines.

  1. Perform the idle speed/mixture adjustments as outlined in Engine Performance and Tune-up . Leave the tachometer connected.
  2.  
  3. Remove the top of the air cleaner.
  4.  
  5. Open the throttle valve slightly and close the choke valve. Next, hold the choke valve with your finger and close the throttle valve. The choke valve is now fully closed.
  6.  
  7. Without depressing the accelerator pedal, start the engine.
  8.  
  9. Check to see that the engine fast idle speed is as noted previously.
  10.  
  11. If the reading on the tachometer is not within specifications, adjust the fast idle speed by turning the fast idle screw.
  12.  
  13. Disconnect the tachometer, install the air cleaner cover, and connect the EGR valve vacuum line if it was disconnected.
  14.  

Reloader Adjustment

See Figure 26

A reloader is used on the 8R-C engine to prevent the throttle valve from opening during automatic choke operation.

  1. When the choke valve is opened 45° from the closed position, the reloader lever should disengage from its stop.
  2.  

Angle, "A'', in the illustration, should be 20° when measured with a gauge.

  1. To adjust, bend the portion of the linkage where angle "'A'' was measured.
  2.  
  3. When the primary throttle valve is fully opened, with the reloader in operating position, the clearance between the secondary throttle valve edge and bore should be 0.35-0.76mm. Measure the clearance with a wire gauge and bend the reloader tab to adjust it.
  4.  
  5. Fully open the choke valve by hand; the reloader lever should be disengaged from its stop by the weight on its link.
  6.  



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Fig. Fig. 26: Measure the angle at "A'' (20°)

Choke Breaker Adjustment

See Figures 27, 28, 29 and 30

1975-79 20R ENGINES
  1. Push the rod which comes out of the upper (choke breaker) diaphragm so that the choke valve opens.
  2.  
  3. Measure the choke valve opening angle. It should be 40°.
  4.  
  5. Adjust the angle, if necessary, by bending the relief lever link.
  6.  

1980 20R AND 1981-88 22R ENGINES
  1. Apply vacuum to the larger of the two diaphragms.
  2.  
  3. Check that the angle of the choke plate is 38°, measured from the horizontal plane. Angle on 1983-88 engines is 42°.
  4.  
  5. If the angle is incorrect, adjust it by bending the choke breaker link.
  6.  
  7. Apply vacuum to both of the diaphragms and check the choke plate angle again. It should be approximately 60° (measured from the horizontal plane as before).
  8.  
  9. If the angle is not within specifications, the choke breaker will require replacement.
  10.  



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Fig. Fig. 27: The choke angle can be measured with an angle gauge, as shown here, or with a piece of cardboard cut to the proper angle--on the 20R, blend the fast idle lever at "A'' to adjust the unloader angle



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Fig. Fig. 28: Carburetor adjustments-18R-C--the 8R-C is identical, except that the idle speed screw is opposite the fast idle screw



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Fig. Fig. 29: Carburetor adjustments-20R



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Fig. Fig. 30: Bend the choke shaft tab to adjust the unloader angle on 8R-C and 18R-C carburetors

Initial Idle Mixture Screw Adjustment

When assembling the carburetor, turn the idle mixture screw the number of turns specified below. After the carburetor is installed, perform the appropriate idle speed/mixture adjustment as detailed in Engine Performance and Tune-up .



8R-C: 2 turns from seating.
 
18R-C: 2 1 / 2 turns from fully closed.
 
20R:
 
1975-79-1 3 / 4 turns from fully closed
 
1980 Federal-2 1 / 2 turns from fully closed
 
1980 California-1 1 / 3 turns from fully closed
 



22R:
 
1982-2 1 / 2 turns from fully closed
 
1983-88-4 turns from fully closed
 
F:1 3 / 4 turns from fully closed
 
2F: 1 3 / 4 turns from fully closed.
 

Kick-Up Adjustment
18R-C AND 20R

See Figure 31

  1. Open the primary throttle valve. On 18R-C engines, the valve should be open 64° from bore; on 20R engines, the valve should be open all the way.
  2.  
  3. The secondary throttle valve-to-bore clearance should be 0.20mm. If not, adjust the clearance by bending the secondary throttle lever.
  4.  



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Fig. Fig. 31: Kick-up adjustment-20R engine

F AND 2F ENGINES

A special blade angle gauge is needed for this adjustment.

  1. Remove the carburetor as previously outlined.
  2.  
  3. Attach the blade angle gauge to the secondary throttle blade.
  4.  
  5. Open the primary throttle blade fully and read the blade angle gauge. The secondary throttle blade should open slightly to an angle of 28° (except California) or 25° (California). If adjustment is necessary, bend the secondary throttle lever as required to attain the proper angle.
  6.  
  7. Detach the blade angle gauge and install the carburetor as previously outlined.
  8.  

Throttle Positioner Adjustment
  1. Apply vacuum to the throttle positioner diaphragm.
  2.  
  3. The throttle valve opening angle should be 16.5° from the horizontal plane. If not, adjust it by turning the adjusting screw.
  4.  

Pump Stroke Adjustment

See Figure 32

Check that the length of the pump stroke (length that the pump lever travels) is 4.0mm. If it is not, it can be adjusted by bending the connecting link.



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Fig. Fig. 32: Adjust the pump stroke at point "A''

Accelerator Pump Adjustment
18R-C, 20R and 2F

Adjust the amount of pump stroke to 4.5mm on 18R-C and 1975-79 20R carburetors by bending the pump rod at point "A''. The 1980 20R adjustment should be 4.0mm. The 2F is 9.5mm.

Automatic Choke Inspection and Adjustment

Steps 1-4 must be performed with the engine cold and turned OFF.

  1. Remove the air cleaner lid.
  2.  
  3. Depress the accelerator pedal. The choke plate should close. If the choke plate closes, proceed to Step 5.
  4.  
  5. If the choke plate does not close, loosen the three screws around the thermostat case.
  6.  


CAUTION
Do not loosen the center housing screw, coolant leakage will occur.

  1. Rotate the case just until the choke plate closes and tighten the case screws.
  2.  
  3. Start the engine and allow it to reach normal operating temperature. If the choke plate opens fully, the choke adjustment is correct. If it does not, loosen the three case screws and rotate the case until the choke is fully open. Tighten the case screws.
  4.  

OVERHAUL



Efficient carburetion depends greatly on careful cleaning and inspection during overhaul, since dirt, gum, water, or varnish in or on the carburetor parts are often responsible for poor performance.

Overhaul your carburetor in a clean, dust-free area. Carefully disassemble the carburetor, referring often to the exploded views. Keep all similar and look-alike parts segregated during disassembly and cleaning to avoid accidental interchange during assembly. Make a note of all jet sizes.

When the carburetor is disassembled, wash all parts (except diaphragms, electric choke units, pump plunger, and any other plastic, leather, fiber, or rubber parts) in clean carburetor solvent. Do not leave parts in the solvent any longer than is necessary to sufficiently loosen the deposits. Excessive cleaning may remove the special finish from the float bowl and choke valve bodies, leaving these parts unfit for service. Rinse all parts in clean solvent and blow them dry with compressed air. Wipe clean all cork, plastic, leather, and fiber parts with a clean, lint-free cloth.

Carburetor solvent is available in various-sized solvent cans, which are designed with a removable small parts basket in the top. The carburetor choke chamber and body, and all small parts can be soaked in this can until clean. These solvent cans are available at most auto parts stores, and are quite handy for soaking other small engine parts.

Blow out all passages and jets with compressed air and be sure that there are not restrictions or blockages. Never use wire or similar tools to clean jets, fuel passages, or air bleeds. Clean all jets and valves separately to avoid accidental interchange.

Check all parts for wear or damage. If wear or damage is found, replace the defective parts. Especially check the following:

  1. Check the float needle and seat for wear. If wear is found, replace the complete assembly.
  2.  
  3. Check the float hinge pin for wear and the float(s) for dents or distortion. Replace the float if fuel has leaked into it.
  4.  
  5. Check the throttle and choke shaft bores for wear or an out-of-round condition. Damage or wear to the throttle arm, shaft, or shaft bore will often require replacement of the throttle body. These parts require a close tolerance of fit; wear may allow air leakage, which could affect starting and idling.
  6.  

Throttle shafts and bushings are not included in overhaul kits. They can be purchased separately.

  1. Inspect the idle mixture adjusting needles for burrs or grooves. Any such condition requires replacement of the needle, since you will not be able to obtain a satisfactory idle.
  2.  
  3. Test the accelerator pump check valves. They should pass air one way but not the other. Test for proper seating by blowing and sucking on the valve. Replace the valve if necessary. If the valve is satisfactory, wash the valve again to remove breath moisture.
  4.  
  5. Check the bowl cover for warped surfaces with a straight edge.
  6.  
  7. Closely inspect the valves and seats for wear and damage, replacing as necessary.
  8.  
  9. After the carburetor is assembled, check the choke valve for freedom of operation.
  10.  

Carburetor overhaul kits are recommended for each overhaul. These kits contain all gaskets and new parts to replace those that deteriorate most rapidly. Failure to replace all parts supplied with the kit (especially gaskets) can result in poor performance and a leaky carburetor later.

Most carburetor manufacturers supply overhaul kits in at least one of three basic types: minor repair; major repair; and gasket kits. Basically, they contain the following, and are available at most auto parts jobbers and Toyota dealers:



Minor Repair Kits -All gaskets, float, needle valve, volume control screw, all diaphragms, and spring for the pump diaphragm.
 
Major Repair Kits -All jets and gaskets, diaphragms, float, needle valve, volume control screw, pump ball valve, main jet carrier and float.
 
Gasket Kits -All gaskets.
 

After cleaning and checking all components, reassemble the carburetor, using new parts and referring to the exploded view. When reassembling, make sure that all screws and jets are tight in their seats, but do not overtighten as the tips will be distorted. Tighten all screws gradually in rotation. Do not tighten needle valves into their seats; uneven jetting will result. Always use new gaskets. Be sure to adjust the float level when reassembling.

 
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