Isuzu Cars and Trucks 1981-1991

Carburetor

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ADJUSTMENT
Fast Idle

The automatic choke fast idle is adjusted by the opening angle of the throttle valve on the carburetor, not by engine speed. Adjusted throttle valve opening at the 1st step of the fast idle cam is 16and#x00B0; (MT) and 18and#x00B0; (AT).

The fast idle should be approximately 3200 rpm after the engine is warm. Disconnect and plug the vacuum line to the distributor, idle compensator and EGR valve.

Float Level
RWD I-MARK AND P'UP
  1. Remove the carburetor and float cover.
  2.  
  3. The fuel level is normal if it is within the mark on the window glass of the float chamber when the engine is stationary.
  4.  
  5. If the level is outside the line, make necessary adjustments by bending the float seat. The needle valve should have an effective stroke of about 1.5mm. Check this measurement between the valve stem and the float seat.
  6.  
  7. Do not bend the needle valve rod when installing the float.
  8.  



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Fig. Float level adjustment RWD I-Mark and P'up

FWD I-MARK
  1. Remove the carburetor and float cover.
  2.  
  3. Check the clearance between the float top and gasket. The measurement should be 1.5mm.
  4.  
  5. Bend tab (A) to adjust the float level.
  6.  
  7. Check the clearance between the float top and gasket at the lowered position of the float.
  8.  
  9. The level should be 44.3mm.
  10.  
  11. Bend tab (B) to adjust the float drop.
  12.  



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Fig. Float adjustment A level adjustment, B drop adjustment



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Fig. Float level adjustment FWD I-Mark and P'up



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Fig. Float drop adjustment FWD I-Mark and P'up

Primary Throttle Valve Adjustment

The primary throttle valve is opened by means of the fast idle adjusting screw to an angle of 16and#x00B0; when the choke valve is completely closed. The primary throttle valve opening angle may be checked as follows:

  1. Close the choke valve completely and measure the clearance between the center of the throttle valve and the wall of the throttle valve chamber. Standard clearance is 1.3 1.5mm.
  2.  
  3. Adjust the throttle valve opening angle with the fast idle adjusting screw.
  4.  


NOTE
Be sure to turn the throttle stop screw all the way in before measuring the clearance.



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Fig. Primary throttle valve adjustment

Kick Lever Adjustment
  1. Turn out the throttle valve adjusting screw to completely close the primary side of the throttle valve.
  2.  
  3. Loosen the locknut on the kick lever screw and turn the screw until it is in contact with the return plate.
  4.  
  5. Tighten the locknut.
  6.  



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Fig. Kick lever adjustment

Choke Valve Opening Adjustment
1988 and 1991 P'UP AND AMIGO
  1. Move the fast idle screw tip against the 2nd step of the fast idle cam.
  2.  
  3. Measure the clearance between the choke valve and the choke valve chamber wall.
  4.  
  5. If the clearance measured is not between 0.8 1.3mm, bend the counter lever tang to adjust.
  6.  



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Fig. Choke valve opening 1988 and 1991 P'up and Amigo

Unloader Adjustment
1988 and 1991 P'up AND AMIGO
  1. Open the primary valve fully.
  2.  
  3. Measure the clearance between the choke valve and the choke valve chamber wall.
  4.  
  5. If the clearance measured is not between 2.5 3.3mm, bend the adjusting lever tang to adjust.
  6.  



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Fig. Unloader adjustment 1988 and 1991 P'up and Amigo

Primary and Secondary Throttle Valve Adjustment
1988 and 1991 P'up AND AMIGO
  1. Slowly open the primary throttle valve until the kick lever tang contacts the return plate.
  2.  
  3. Measure the clearance between the choke valve and the choke valve chamber wall.
  4.  
  5. If the clearance measured is not between 7.0 and 198.5mm, bend the kick lever tang to adjust.
  6.  



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Fig. Primary and secondary valve adjustment 1988 and 1991 P'up and Amigo

CARBURETOR REMOVAL AND INSTALLATION
I-Mark
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner wing nut and disconnect the rubber hoses from the clips on the air cleaner cover.
  4.  
  5. Remove the bracket bolts, if equipped, at the air cleaner and remove the air cleaner cover and filter element.
  6.  
  7. Disconnect the hot air hose (to the hot air duct), the air hose to the air pump at the air cleaner and the vacuum hose at the joint nipple side of the intake manifold.
  8.  
  9. Loosen the bolt clamping the air cleaner to the carburetor. Separate the air cleaner body from the carburetor but do not remove it completely.
  10.  
  11. Disconnect the PCV hose (to the camshaft cover), the rubber hoses to the check and relief valve. Remove the air cleaner body.
  12.  
  13. Disconnect the vacuum hoses from the EGR valve.
  14.  
  15. Disconnect the choke control wire.
  16.  
  17. Disconnect the lead from the throttle solenoid.
  18.  
  19. Disconnect the throttle linkage return spring.
  20.  
  21. Disconnect the accelerator linkage and detent cable, if so equipped.
  22.  
  23. Disconnect the fuel line at the carburetor.
  24.  
  25. Remove the carburetor-to-manifold nuts and the carburetor.
  26.  

To install:

  1. Using a new gasket, install the carburetor to the intake manifold.
  2.  
  3. Connect the fuel line and the accelerator linkage to the carburetor.
  4.  
  5. Connect the throttle linkage return spring, the throttle solenoid lead, the choke control wire and the vacuum hoses to the EGR and the PCV.
  6.  
  7. Install the air cleaner and any necessary hoses.
  8.  
  9. Start the engine and check for fuel leaks.
  10.  

P'up, Amigo and Trooper
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the PCV and AIR hose.
  4.  
  5. Remove the air cleaner assembly with the TCA vacuum hose and air duct.
  6.  
  7. Remove the throttle return spring.
  8.  
  9. Label and disconnect the emission control vacuum hoses.
  10.  
  11. Disconnect the lead wire connectors and accelerator cable.
  12.  
  13. Release the fuel pressure and disconnect the fuel pipes.
  14.  
  15. Remove the carburetor retaining nuts and carburetor.
  16.  



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Fig. Carburetor removal P'up, Amigo and Trooper

To install:

  1. Install the carburetor, gaskets and retaining nuts.
  2.  
  3. Connect the fuel pipes.
  4.  
  5. Connect the lead wire connectors and accelerator cable.
  6.  
  7. Connect the emission control vacuum hoses.
  8.  
  9. Install the throttle return spring.
  10.  
  11. Install the air cleaner assembly with the TCA vacuum hose and air duct.
  12.  
  13. Connect the PCV and AIR hose.
  14.  
  15. Connect the negative battery cable, start the engine and check for leaks.
  16.  

Idle Speed Adjustment

Refer to the "Idle Speed" section in Engine Performance and Tune-up.

Idle Mixture Adjustment

Refer to the "Idle Mixture" section in Engine Performance and Tune-up.

OVERHAUL
RWD I-Mark and 1981-87 P'up
DISASSEMBLY

When disassembling or reassembling the carburetor, use the proper tools. Keep the disassembled parts in separate groups, according to the systems from which they were removed, to avoid interchanging of parts. Clean all disassembled parts in carburetor cleaner and clean out orifices with compressed air.

  1. Remove the carburetor from the vehicle and clean the outside dirt using engine cleaner.
  2.  
  3. Disconnect the accelerator pump lever.
  4.  
  5. Disconnect the rubber hose from the slow actuator.
  6.  
  7. Remove the throttle return spring. Flattening the harness clips under the choke housing and remove the wires from the clips. Disconnect the choke wires.
  8.  
  9. Remove the fuel nipple and strainer.
  10.  
  11. Disconnect the choke connecting rod from the counter lever by removing the circlip.
  12.  
  13. Remove the choke chamber from the float chamber and remove assembly.
  14.  
  15. Remove the circlip between the diaphragm and secondary throttle lever. Loosen three diaphragm chamber attaching screws, then remove the diaphragm assembly.
  16.  
  17. Separate the float chamber from the throttle body.
  18.  
  19. Remove the slow actuator and accelerator pump assembly.
  20.  
  21. Remove the float needle valve assembly.
  22.  
  23. Remove the main actuator being careful not to damage the rubber seal or lose the float collar.
  24.  
  25. Disassemble the diaphragm chamber and check diaphragm for damage.
  26.  
  27. Remove the jets from the upper part of the float chamber.
  28.  
  29. Remove the injector weight plug, weight, check ball and spring.
  30.  
  31. Remove the two main jets plugs and jets.
  32.  
  33. Remove the primary slow air bleed from the choke chamber.
  34.  


NOTE
The screws retaining the primary throttle valve, secondary throttle valve and choke valve are carefully tightened and locked with thread locking compound.

  1. Inspect all parts for cracks, deterioration and corrosion. Replace if necessary.
  2.  



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Fig. Exploded view of the carburetor RWD I-Mark and 1981 and 1987 P'up

ASSEMBLY

NOTE
When reassembling the accelerator pump, fill the cylinder with fuel and check to be sure fuel is injected smoothly.

  1. Install the primary slow air bleed into the choke chamber.
  2.  
  3. Install the two main jets plugs and jets.
  4.  
  5. Install the injector weight plug, weight, check ball and spring.
  6.  
  7. Install the jets to the upper part of the float chamber.
  8.  
  9. Reassemble the diaphragm chamber.
  10.  
  11. Install the main actuator being careful not to damage the rubber seal or lose the float collar.
  12.  
  13. Install the float needle valve assembly.
  14.  
  15. Install the slow actuator and accelerator pump assembly.
  16.  
  17. Install the float chamber to the throttle body and tighten screws.
  18.  
  19. Install the circlip between the diaphragm and secondary throttle lever. Install the diaphragm assembly.
  20.  
  21. Install the choke chamber to the float chamber.
  22.  
  23. Connect the choke connecting rod to the counter lever and install the circlip.
  24.  
  25. Install the fuel nipple and strainer.
  26.  
  27. Install the throttle return spring. Connect the choke wires.
  28.  
  29. Connect the rubber hose to the slow actuator.
  30.  
  31. Connect the accelerator pump lever.
  32.  
  33. Install the carburetor to the vehicle, start the engine and check for leaks.
  34.  

FWD I-Mark
DISASSEMBLY
  1. Remove the carburetor from the vehicle and clean with engine cleaner.
  2.  
  3. Remove the pump arm spring, pump arm assembly and connecting rod.
  4.  
  5. Remove the air horn screws and air horn assembly.
  6.  
  7. Remove the float pin and float assembly.
  8.  
  9. Remove the gasket and float valve.
  10.  
  11. Remove the packing and plunger.
  12.  
  13. Remove the feedback solenoid and E-clip.
  14.  
  15. Remove the choke piston assembly, throttle return spring and secondary spring.
  16.  
  17. Remove the Diaphragm chamber and disassemble chamber to check diaphragm.
  18.  
  19. Remove the slow cut solenoid valve and pump return spring.
  20.  
  21. Remove the pump strainer and check ball.
  22.  
  23. Remove the throttle opener.
  24.  
  25. Remove the primary and secondary plug, packing and main jet.
  26.  
  27. Remove the primary and secondary small venturis.
  28.  
  29. Remove the main air bleed jets.
  30.  
  31. Remove the plug, spring, pump weight and check ball.
  32.  
  33. Remove the plug, slow jet and idle-up jet.
  34.  
  35. Remove the mixture by-pass solenoid valve and throttle position sensor.
  36.  



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Fig. Exploded view of the carburetor FWD I-Mark 4XC1-U

ASSEMBLY
  1. Install the mixture by-pass solenoid valve and throttle position sensor.
  2.  
  3. Install the plug, slow jet and idle-up jet.
  4.  
  5. Install the plug, spring, pump weight and check ball.
  6.  
  7. Install the main air bleed jets.
  8.  
  9. Install the primary and secondary small venturis.
  10.  
  11. Install the primary and secondary plug, packing and main jet.
  12.  
  13. Install the throttle opener.
  14.  
  15. Install the pump strainer and check ball.
  16.  
  17. Install the slow cut solenoid valve and pump return spring.
  18.  
  19. Install the Diaphragm chamber.
  20.  
  21. Install the choke piston assembly, throttle return spring and secondary spring.
  22.  
  23. Install the feedback solenoid and E-clip.
  24.  
  25. Install the packing and plunger.
  26.  
  27. Install the gasket and float valve.
  28.  
  29. Install the float pin and float assembly.
  30.  
  31. Install the air horn screws and air horn assembly.
  32.  
  33. Install the pump arm spring, pump arm assembly and connecting rod.
  34.  
  35. Install the carburetor to the vehicle, start the engine and check for leaks.
  36.  

1988 and 1991 P'up and Amigo
DISASSEMLY
  1. Remove the carburetor from the vehicle and clean the outside with engine cleaner.
  2.  
  3. Major component disassembly: remove the assist spring, pump rod split pin with washer and pump lever and split pin.
  4.  
  5. Remove the return spring and main spring.
  6.  
  7. Remove the slow cut solenoid, fast idler cam and spring.
  8.  
  9. Remove the choke chamber assembly.
  10.  
  11. Remove the throttle chamber screws and float chamber assembly from the throttle chamber.
  12.  
  13. Minor component disassembly: remove the vent cover and duty solenoid.
  14.  
  15. From the choke chamber, remove the fuel nipple, fuel filter and level gauge cover.
  16.  
  17. Remove the float and collar from the housing.
  18.  
  19. Remove the needle valve assembly.
  20.  
  21. Remove the secondary and primary main jets.
  22.  
  23. Remove the accelerator pump piston, pump cover, return spring and pump set screw.
  24.  
  25. Remove the injector spring, weight and taper plug.
  26.  
  27. Remove the slow jet spring, primary and secondary slow jet.
  28.  
  29. Remove the primary and secondary main air bleeds from the float chamber.
  30.  
  31. Throttle chamber disassembly:
  32.  


NOTE
Do not disassembly the throttle chamber assembly unless damaged or not functioning properly. Clean and reassemble as a complete unit.

  1. Remove the diaphragm chamber cover, spring and diaphragm.
  2.  
  3. Remove the idler adjusting screw, throttle adjusting screw and throttle shaft nut and washer.
  4.  
  5. Remove the spring hanger and shaft collar.
  6.  
  7. Remove the fast idler adjusting lever and screw.
  8.  
  9. Remove the kick lever, return spring, return plate and sleeve.
  10.  
  11. Remove the adjusting lever from the throttle chamber.
  12.  



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Fig. Major carburetor component disassembly 1988 and 1991 P'up



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Fig. Minor carburetor component disassembly 1988 and 1991 P'up



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Fig. Throttle chamber disassembly 1988 and 1991 P'up

ASSEMBLY
  1. If throttle chamber was disassembled: install the kick lever, return spring, return plate and sleeve.
  2.  
  3. Install the fast idler adjusting lever and screw.
  4.  
  5. Install the spring hanger and shaft collar.
  6.  
  7. Install the idler adjusting screw, throttle adjusting screw and throttle shaft nut and washer.
  8.  
  9. Install the diaphragm chamber cover, spring and diaphragm.
  10.  
  11. Minor component assembly: install the primary and secondary main air bleeds to the float chamber.
  12.  
  13. Install the slow jet spring, primary and secondary slow jet.
  14.  
  15. Install the injector spring, weight and taper plug.
  16.  
  17. Install the accelerator pump piston, pump cover, return spring and pump set screw.
  18.  
  19. Install the secondary and primary main jets.
  20.  
  21. Install the needle valve assembly.
  22.  
  23. Install the float and collar to the housing.
  24.  
  25. To the choke chamber, install the fuel nipple, fuel filter and level gauge cover.
  26.  
  27. Install the vent cover and duty solenoid.
  28.  
  29. Install the throttle chamber screws and float chamber assembly to the throttle chamber.
  30.  
  31. Install the choke chamber assembly.
  32.  
  33. Install the slow cut solenoid, fast idler cam and spring.
  34.  
  35. Install the return spring and main spring.
  36.  
  37. Major component assembly: install the assist spring, pump rod split pin with washer and pump lever and split pin.
  38.  
  39. Install the carburetor to the vehicle, start the engine and check for leaks.
  40.  

 
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