Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989

Carburetor

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ADJUSTMENTS



Fast Idle
1978 GLC

This adjustment can be performed only with the carburetor removed from the engine.

  1. Close the choke valve fully, and measure the clearance between the lower edge of the throttle and the throttle bore with a wire feeler gauge. The dimension is 0.05-0.06 in. (1.2-1.5mm).
  2.  
  3. If necessary adjust by bending the rod which connects the choke shaft and fast idle cam.
  4.  

1979-85 GLC AND 1979-82 626

See Figures 1 and 2

  1. On the 1.4L GLC engine, remove the bimetal cover.
  2.  
  3. Using your finger close the choke valve fully.
  4.  



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Fig. Fig. 1: Fast idle cam adjustment-1.4L engine



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Fig. Fig. 2: Fast idle cam adjustment-2.0L engine

  1. Make sure the fast idle cam is on the 1st position (3rd position for the 1.5L GLC engine).
  2.  
  3. The throttle valve opening (clearance G) should be:

    1.4L engine: 0.06 in. (1.4mm) in 1979; 0.04 in. (1.04mm) in 1980
     
    1.5L engine: 0.03 in. (0.66mm)
     
    2.0L engine: 0.04 in. (1.04mm) in 1979; 0.02 in. (0.61mm) for 1980-82
     

  4.  

  1. Adjust by turning the adjustment screw.
  2.  

Turn the adjustment screw clockwise to increase the clearance.

RX-7

See Figure 3

To adjust the fast idle, it is necessary for the carburetor to be removed from the car.

  1. Remove the carburetor from the vehicle.
  2.  
  3. Fully close the check valve.
  4.  



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Fig. Fig. 3: Fast idle adjustment-RX-7

  1. Measure the clearance between the primary throttle valve and the wall of the throttle bore. Clearances are as follows:

    1979 (California) and 1980-0.05-0.06 in. (1.30-1.50mm)
     
    1979 (49 states, Canada) and 1981-0.035-0.043 in. (0.90-1.10mm)
     
    1982 (All models)-0.03-0.04 in. (0.8-1.0mm)
     
    1983-85 (All models)-0.04-0.05 in. (1.0-1.2mm)
     

  2.  

  1. If clearance is not correct, bend the fast idle rod until proper clearance is obtained.
  2.  

Float and Fuel Level
GLC
  1. Invert the air horn and lower the float slowly until the seat lip just touches the needle valve. Measure the clearance between the float and air horn gasket surface (remove the gasket). It should be 0.43 in. (11mm). Bend the float seat lip as necessary to correct the dimension.
  2.  
  3. With air horn still inverted, lift the float upward until the float stop contacts the air horn. Measure the clearance between the top of the needle valve and the float seat lip. It should be 0.05-0.07 in. (1.3-1.7mm). If not, bend the float stop until the clearance is correct.
  4.  

1979-82 626
  1. Invert the air horn and allow the float to lower by its own weight.
  2.  
  3. Measure the clearance between the float and the air horn bowl. The clearance should be 0.43 in. (11mm). Bend the float seat lip to adjust.
  4.  
  5. Turn the air horn to the normal position and allow the float to lower by its own weight.
  6.  
  7. Measure the distance between the bottom of the float and the air horn bowl. The distance should be 1.8 in. (46mm). Bend the float stopper to adjust.
  8.  

1983-87 626

See Figures 4 and 5

  1. Invert the air horn and allow the float to lower by its own weight.
  2.  
  3. Measure the clearance between the float and the air horn bowl. The clearance should be 0.53 in. (13.5mm). Bend the float seat lip to adjust.
  4.  



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Fig. Fig. 4: Float to air horn bowl adjustment (clearance "H")-1983-87 626



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Fig. Fig. 5: Float bottom to air horn bowl adjustment (clearance "L")-1983-87 626

  1. Turn the air horn to the normal position and allow the float to lower by its own weight.
  2.  
  3. Measure the distance between the bottom of the float and the air horn bowl. The distance should be 1.93 in. (49mm). Bend the float stopper to adjust.
  4.  

1979-85 RX-7

See Figures 6 and 7

The float bowl fuel level can be checked through the sight glass in the carburetor body. Fuel level should be in the center of the glass. Be sure to check the level of both float chambers.

  1. Remove the air cleaner and remove the top part of the carburetor (the air horn).
  2.  
  3. Turn the air horn upside down and allow the float to rest, as shown in the illustration. Measure clearance H between the float and the air horn gasket. Clearance should be 0.61-0.65 in. (15.5-16.5mm). If clearance is not correct, bend the float seat lip as required to adjust.
  4.  
  5. Turn the air horn to normal position and measure clearance L between the bottom of the float and the air horn gasket. Distance should be 1.99-2.03 in. (50.5-51.5mm). Adjust by bending the float stopper.
  6.  



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Fig. Fig. 6: Float to air horn bowl adjustment (clearance "H")-RX-7



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Fig. Fig. 7: Float bottom to air horn bowl adjustment (clearance "L")-RX-7

Throttle Linkage
PISTON ENGINES
  1. Check the accelerator pedal position; it should be lower than the brake pedal.
  2.  
  3. If necessary, adjust the nut on the linkage above the pedal to obtain the proper height.
  4.  
  5. Check the free-play of the cable at the carburetor. It should be 0.04-0.12 in. (1-3mm). If not, adjust by turning the clevis nut.
  6.  
  7. The accelerator pedal distance below the brake pedal should be 1.78-2.17 in. (45-55mm) for the 1983-85 GLC.
  8.  
  9. On vehicles other than 1983-85 GLCs, depress the accelerator pedal to the floor and confirm that the throttle valve is fully open. Adjust as necessary, by using the adjusting bolt or nut on the linkage above the accelerator pedal.
  10.  

ROTARY ENGINES

See Figure 8

To check the adjustment of the throttle linkage, remove the air cleaner and observe the position of the two primary throttle valves when the accelerator is fully depressed. The valves should be in a vertical (wide open) position. When checking the throttle linkage, also make sure that the accelerator cable does not bind or stick in its outer cable.

  1. Measure accelerator pedal height. It should be 1.46-1.85 in. (37-47mm) lower than the brake pedal. If not, adjust it using nut A in the illustration.
  2.  



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Fig. Fig. 8: Throttle linkage adjustment-RX-7

  1. Check the free-play of the cable at the carburetor by applying light finger pressure to the middle of the cable. It should be between 0.04-0.12 in. (1-3mm). If not, adjust it using nut B in the illustration.
  2.  
  3. Fully depress the accelerator pedal and check to see that the primary throttle valves are wide open. If not, adjust stopper bolt C in the illustration.
  4.  

Semi-Automatic Choke
1979-80 RX-7

See Figures 9, 10 and 11

You will need a vacuum source of more than 19.7 in. Hg. (500 mm Hg) to make this adjustment.

  1. Disconnect the vacuum sensing tube from the vacuum diaphragm.
  2.  
  3. Pull the choke lever link out fully and hold it in this position.
  4.  
  5. Apply vacuum to the vacuum diaphragm.
  6.  
  7. Check the clearance between the top of the choke valve and the throttle bore body, with a wire gauge.
  8.  
  9. Measure the temperature of the bimetal spring, then compare it and the clearance with the specifications given in the accompanying charts.
  10.  
  11. If clearance is not within specifications, adjust it by turning the adjusting nut.
  12.  



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Fig. Fig. 9: Choke valve clearance chart-1979 RX-7



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Fig. Fig. 10: Choke valve clearance chart-1980 RX-7 (49 states and Canada)



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Fig. Fig. 11: Choke valve clearance chart-1980 RX-7 (California)

Primary Throttle Valve Initial Opening Angle
1979-80 RX-7

See Figure 12

This adjustment should be performed when the throttle body, throttle lock lever and/or adjusting screw have been tampered with or changed.

  1. Remove the carburetor from the engine.
  2.  
  3. Loosen the locknut and turn the adjusting screw to the left (counterclockwise).
  4.  
  5. Close the throttle valve completely and gradually tighten the adjusting screw until it just touches the throttle lock lever. Tighten the screw an additional 1 / 8 - 3 / 8 of a turn, then tighten the locknut.
  6.  
  7. Measure the clearance and the angle of opening for the primary throttle valve when closed. Clearance should be 0.002 in. (0.05mm) and the angle of opening should be 1 degree. If not, reset the throttle opening with the adjusting screw.
  8.  



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Fig. Fig. 12: Primary throttle valve adjustment-1979-80 RX-7

Automatic Choke
GLC AND 626

See Figure 13

  1. Fully depress the accelerator pedal to make sure the choke valve closes properly.
  2.  
  3. Check for binding in the choke valve by pushing it with your finger.
  4.  
  5. Make sure that the bimetal cover index mark is set to the center choke housing index mark; adjust if necessary.
  6.  
  7. Check the automatic choke heater source wiring for proper connection.
  8.  
  9. Start the engine and let it idle.
  10.  
  11. After the engine warms up, check that the choke valve is fully opened.
  12.  
  13. If the valve does not open fully, and the automatic choke heater source wiring is normal, replace the bimetal cover.
  14.  



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Fig. Fig. 13: The bimetal cover index mark should be set to the center mark on the choke housing-GLC and 626

RX-7

Perform this check with the engine "overnight" cold.

  1. With a cold engine and the ignition switch in the OFF position, pull the choke knob out fully and make sure the knob returns automatically.
  2.  
  3. Connect a tachometer to the engine.
  4.  
  5. Start the engine and use the choke knob to set the idle speed to 2,000 rpm. Allow the engine to run at this speed and observe the temperature gauge. The choke knob should return back to its original position when the pointer on the gauge rises to just about the low mid-range portion of the scale.
  6.  

Choke Unloader
GLC AND 626
  1. Close the choke valve fully, then open the primary throttle valve fully.
  2.  
  3. Measure the choke valve clearance. The clearance should be 0.08-0.09 in. (2.00-2.40mm) for the GLC and 0.10-0.14 in. (2.65-3.45mm) for the 626.
  4.  
  5. Bend the tab to adjust.
  6.  

Secondary Throttle Valve
GLC and 626

See Figure 14

  1. The secondary throttle valve starts to open when the primary throttle valve is open 49-51 degrees, and opens completely at the same time that the primary throttle valve is fully open.
  2.  
  3. Check the clearance between the primary throttle valve and the wall of the throttle bore when the secondary throttle valve starts to open.
  4.  
  5. The clearance should be:

    Rear wheel drive GLC hatchback: 0.21-0.26 in. (5.40-6.60mm)
     
    Rear wheel drive GLC wagon: 0.29-0.32 in. (7.30-8.25mm)
     
    Front wheel drive GLC-except 1982: 0.21-0.26 in. (5.40-6.60mm); 1982: 0.29-0.33 in. (7.30-8.50mm)
     
    626: 0.24-0.28 in. (6.20-7.20mm)
     

  6.  

  1. To adjust the clearance, bend the connecting rod.
  2.  



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Fig. Fig. 14: Secondary throttle valve adjustment-GLC and 626

Throttle Sensor
RX-7

See Figures 15, 16, 17 and 18

The throttle sensor should be checked, and adjusted as necessary, whenever the idle speed has been adjusted.

  1. Warm up the engine to its normal operating temperature.
  2.  
  3. Connect a suitable tachometer to the engine.
  4.  
  5. Detach the brown connector, as illustrated.
  6.  



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Fig. Fig. 15: Unfasten the brown wiring connector



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Fig. Fig. 16: When adjusting the RX-7 throttle sensor, connect a pair of voltmeters as illustrated

  1. Using two voltmeters, connect a negative probe to each terminal (GY and LgY) of the connector.
  2.  

A two-bulb test light can be assembled (as illustrated) and used in place of the voltmeters.

  1. Connect the positive probe of each voltmeter to the B terminal of the alternator.
  2.  
  3. Start the engine.
  4.  
  5. Quickly decelerate the engine speed from 3,000 rpm and check that current flows to both terminals simultaneously. The engine speed should be 1,000-1,200 rpm.
  6.  



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Fig. Fig. 17: A two-bulb test light can be assembled and used instead of the voltmeters



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Fig. Fig. 18: After turning the throttle sensor adjusting screw, reposition its protective cap

  1. If current does not start to flow to both terminals simultaneously, remove the cap from the throttle sensor adjusting screw.
  2.  
  3. Adjust the timing of the current flowing to voltmeter A (connected to LgY) by turning the throttle sensor adjusting screw. When the screw is turned in (clockwise), current will begin to flow earlier; when the screw is turned out (counterclockwise), current will begin to flow later.
  4.  
  5. When adjustment is complete, install the cap on the adjusting screw. Remove the test equipment and fasten the brown connector.
  6.  

Hot Start Assist System

When a rotary engine is hot, the best way to start it is to open the throttle fully. To save the driver from this task, Mazda has equipped the RX-7 with a hot start assist motor which opens the throttle while engaging the starter on a warm engine. The motor is mounted on the left side of the engine compartment and is attached to the carburetor linkage by a cable. The system can be easily checked as follows: with the engine warm, open the hood and have an assistant watch the cable at the hot start assist motor while you engage the starter. The cable should pull back while the starter is engaged and release as soon as the starter is disengaged. If the cable requires adjustment, proceed as follows:

1979-83 RX-7

See Figure 19

  1. Remove the lock spring on the cable bracket.
  2.  
  3. Slowly pull the outer cable until the hot start lever just touches the stopper lever. Check the clearance between the cable bracket and the locknut of the cable. Clearance should be 0.05 in. (1.25mm). Adjust the clearance by turning the locknut.
  4.  
  5. Install the lock spring.
  6.  

1984-85 RX-7

See Figure 20

  1. Pull the start assist motor inner cable until the stopper lever makes contact with the start lever and check the free-play; it should be 0.04-0.08 in. (1-2mm).
  2.  
  3. If the free-play is not as specified, loosen the screw and adjust it.
  4.  



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Fig. Fig. 19: Hot start assist cable adjustment-1979-83 RX-7



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Fig. Fig. 20: Hot start assist cable adjustment-1984-85 RX-7

REMOVAL & INSTALLATION



Piston Engines
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Disconnect the accelerator cable. If equipped, disconnect the cruise control cable.
  6.  
  7. Disengage all wire connections, vacuum sensing tubes and fuel hoses.
  8.  
  9. Unfasten and remove the carburetor. Cover the opening to keep dirt out of the intake manifold.
  10.  
  11. Installation is the reverse of removal. Be sure to use a new carburetor gasket. Adjust the throttle linkage as previously described.
  12.  

Rotary Engines

See Figure 21

The RX-7 is equipped with a 4-barrel carburetor which is similar in design to the carburetors used on piston engines. Two primary barrels feed a constant mixture of air and fuel to the rotors. The primary barrels are supplemented by two vacuum operated secondary barrels during acceleration and high speed driving.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Label and unfasten all electrical connections from the carburetor and necessary surrounding components.
  6.  
  7. Label and disconnect all necessary vacuum hoses.
  8.  
  9. Disconnect the oil metering pump linkage at the carburetor.
  10.  
  11. Disconnect the hot start assist cable, along with the choke and accelerator cables, from the carburetor. Route the cables off to the side and out of the way.
  12.  
  13. Disconnect the air vent hose. On all except California vehicles, disconnect the sub-zero start assist fluid hose.
  14.  
  15. Disconnect the fuel return and the main fuel hoses. Plug the main fuel line to prevent leakage.
  16.  
  17. Disconnect the metering oil pump lines from the carburetor. Disconnect the air vent solenoid valve coupler.
  18.  
  19. Remove the carburetor attaching nuts and remove the carburetor. Cover the intake manifold with masking tape to prevent dirt and debris from entering the engine. Discard the old gasket; a new one should be used during assembly to assure proper vacuum seal.
  20.  

To install:
  1. Place the new gasket onto the intake manifold, then install the carburetor over the mounting studs and onto the gasket.
  2.  
  3. Install and tighten the attaching nuts.
  4.  
  5. Complete the remainder of the installation in reverse of the removal procedure. Adjust the throttle linkage as previously described.
  6.  
  7. Connect the negative battery cable.
  8.  



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Fig. Fig. 21: Carburetor removal-RX-7

OVERHAUL



Carburetor rebuilding kits usually include specific procedures and exploded views for order of assembly and disassembly, therefore, only general applicable rebuilding suggestions are provided here. 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. Be sure to keep all similar/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 or allow them to air dry. Wipe clean all cork, plastic, leather, and fiber parts with a clean, lint-free cloth.

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

Check all parts for wear or damage; replace all defective parts. During inspection, pay careful attention to 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 check 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 usually included in overhaul kits, but they can often 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 straightedge.
  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 later.

Some carburetor manufacturers supply overhaul kits of three basic types: minor repair; major repair; and gasket kits. Basically, they contain the following:

Minor Repair Kits:


All gaskets
 
Float needle valve
 
Volume control screw
 
All diaphragms
 
Spring for the pump diaphragm
 

Major Repair Kits:


All jets and gaskets
 
All diaphragms
 
Float needle valve
 
Volume control screw
 
Pump ball valve
 
Main jet carrier
 
Float
 
Complete intermediate rod
 
Intermediate pump lever
 
Complete injector tube
 
Some cover hold-down screws and washers
 

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 could 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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