GM Full-Size Trucks 1980-1987 Repair Guide

Carburetor

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IDENTIFICATION



See Figure 1

Carburetor identification numbers will generally be found in the following locations:



ME: Stamped on the vertical portion of the float bowl, adjacent to the fuel inlet nut.
 
E2SE, 2SE: Stamped on the vertical surface of the float bowl adjacent to the vacuum tube.
 
M2MC: Stamped on the vertical surface of the left rear corner of the float bowl.
 
E4ME, 4MV, M4MC, M4ME: Stamped on the vertical section of the float bowl, near the secondary throttle lever.
 



Click image to see an enlarged view

Fig. Fig. 1: Carburetor identification number, ME type carburetor shown

1ME 1 bbl Carburetor

The carburetors are 1 bbl, single stage units. The "M" in the model identification number indicates that the carburetor is of a Modified primary metering "open loop" design. The "E" indicates that it has an integral, electric choke and the "F" indicates that it has an adjustable wide-open mixture control.

These models have three major assemblies: the air horn, float bowl, and throttle body. They have six basic operating systems:

  1. Float
  2.  
  3. Idle
  4.  
  5. Main Metering
  6.  
  7. Power
  8.  
  9. Pump
  10.  
  11. Choke
  12.  

E2SE 2-bbl Carburetor

The model E2SE, introduced on Chevrolet pick-up trucks in 1983, is designed as part of the GM Computer Command Control System (C3). An electrically operated mixture control solenoid differentiates the E2SE from the conventional 2SE series.

A plunger in the end of the above mentioned solenoid is submerged in fuel in the fuel chamber of the float bowl. The plunger is controlled, or pulsed, by electrical signals received from the Electronic Control Module (ECM). The solenoid system is used to control the air/fuel mixture in the primary bore of the carburetor.

The mode E2SE also has a Throttle Position Sensor (TPS) mounted in the float bowl and is used to signal the ECM as throttle position changes occur. As throttle position changes, a tang on the pump lever moves the TPS plunger, modifying an electrical signal to the ECM. This signal is used in conjunction with signals from various other engine sensors by the ECM to control various engine operating modes.

M2M 2 bbl Carburetor

These Rochester models are two barrel carburetors with three major assemblies: the air horn, float bowl, and throttle body. They have six basic operating systems:

  1. Float
  2.  
  3. Idle
  4.  
  5. Main Metering
  6.  
  7. Power
  8.  
  9. Pump
  10.  
  11. Choke
  12.  

The first "M" in the model identification number indicates that the carburetor is of a Modified primary metering "open loop" design. The "2M" is the model designation, indicating it is a two barrel carburetor. The remaining letters designate specific features as follows:



C - It has an integral Hot Air Choke.
 
E - Has an electric choke.
 

The carburetor identification number is stamped vertically on the float bowl. Refer to this number before servicing the carburetor. If replacing the float bowl assembly, follow the instructions in the service package and stamp or engrave the number on the new float bowl.

A single float chamber supplies fuel to all carburetor bores. A float, float needle with pull clip and a float needle seat are used to control the level of fuel in the float chamber.

The accelerator pump system on all models use a throttle actuated pump plunger, operating in the pump well. The pump provides extra fuel during quick throttle openings.

An electrically heated choke coil on 1981 models provides the choke valve closing force for cold startup and for correct opening time during warm-up. A vacuum break assembly controls initial choke valve opening at startup to provide sufficient air flow to the engine. An unloader tang on the throttle lever forces the choke valve to open to purge a flooded engine when the accelerator is pressed to the floor. The fast idle cam, following choke valve movement, acts as a graduated throttle stop to provide increased idle speed during warm-up.

The electric Idle Stop Solenoid (ISS) provides the desired engine idle speed, and prevents dieseling when the ignition is switched off.

M4M 4 bbl Carburetors

These Rochester models are four barrel, two stage carburetors with three major assemblies: the air horn, float bowl, and throttle body. They have six basic operating systems:

  1. Float
  2.  
  3. Idle
  4.  
  5. Main Metering
  6.  
  7. Power
  8.  
  9. Pump
  10.  
  11. Choke
  12.  

The first "M" in the model identification number indicates that the carburetor is of a Modified primary metering "open loop" design. The "4M" is the model designation, indicating it is a four barrel carburetor. The remaining letters designate specific features as follows:



C - It has an integral Hot Air Choke.
 
D - Dual capacity pump valve and a combined mixture control/dual capacity pump solenoid assembly.
 
E - Has an electric choke.
 
F - Has an adjustable wide open throttle mixture control.
 

The carburetor identification number is stamped vertically on the float bowl near the secondary throttle lever. Refer to this number before servicing the carburetor. If replacing the float bowl assembly, follow the instructions in the service package and stamp or engrave the number on the new float bowl.

A single float chamber supplies fuel to all carburetor bores. A float, float needle with pull clip and a float needle seat are used to control the level of fuel in the float chamber. A vacuum-operated power piston and metering rods control the air/fuel metering in the primary bores of the carburetor. Tapered metering rods are attached to the power valve piston assembly and move in fixed metering jets to provide the fuel flow for varying engine demands. A factory-set adjustable part throttle screw, used on all models, precisely positions the tapered portion of the metering rods in the jets. On M4MEF models, the factory-set rich stop adjusting bushing precisely positions the enrichment portion of the metering rods in the jets.

Air valves and tapered metering rods control the air/fuel mixture in the secondary bores during increased engine air flow at wide open throttle. On M4MEF models, the factory-set secondary well air bleed adjusting screw provides additional control of the air/fuel mixture during wide open throttle (WOT).

The accelerator pump system on all models uses a throttle actuated pump plunger, operating in the pump well. The pump provides extra fuel during quick throttle openings.

An electrically heated choke coil provides the choke valve closing force for cold startup and for correct opening time during warm-up. A vacuum break assembly controls initial choke valve opening at startup to provide sufficient air flow to the engine. An unloader tang on the throttle lever forces the choke valve to open to purge a flooded engine when the accelerator is pressed to the floor. The fast idle cam, following choke valve movement, acts as a graduated throttle stop to provide increased idle speed during warm-up.

The electric Idle Stop Solenoid (ISS) on Federal V8 engines with manual transmission provides the desired engine idle speed, and prevents dieseling when the ignition is switched off. A vacuum-operated Throttle Kicker assembly on California V8 engines retards throttle closing during deceleration to improve emission control. Vacuum to the kicker is controlled by the Throttle Return Control system.

REMOVAL & INSTALLATION



See Figures 2 through 14

Model 1M Series Carburetors

WARNING
Before removing the carburetor allow the engine to cool completely to prevent ignition and possible fire from hot engine components such as the exhaust manifold.

  1. Disconnect the negative battery cable
  2.  
  3. Remove the air cleaner and its gasket.
  4.  
  5. Disconnect the fuel and vacuum lines from the carburetor.
  6.  


WARNING
Keep a rag handy to soak up any gasoline that might spill on any other components. Immediately dispose of the rag in a container approved for flammable or combustible refuse.

  1. Disconnect the electrical connectors for the choke and idle solenoid.
  2.  
  3. Disconnect the throttle linkage.
  4.  
  5. Remove the carburetor attaching nuts, gasket or insulator, and remove the carburetor.
  6.  

To install:
  1. Install new heat shield and insulator gaskets to the intake manifold.
  2.  
  3. Install the carburetor with the float bowl filled with gasoline to ease starting the engine later. Tighten both nuts to 36 inch lbs. (4.1 Nm) and then tighten both nuts to 16 ft. lbs. (22 Nm).
  4.  
  5. Reconnect the throttle linkage
  6.  
  7. Reconnect the electrical connectors for the choke and idle solenoid.
  8.  
  9. Reconnect the fuel and vacuum lines from the carburetor.
  10.  
  11. Reconnect the negative battery cable
  12.  
  13. Check for fuel leaks by cranking the engine a little but not starting it. Be sure to check not only at the carburetor fuel line fitting but also at the fuel pump.
  14.  
  15. Install the air cleaner and its gasket.
  16.  



Click image to see an enlarged view

Fig. Fig. 2: Before removing the carburetor, tag all hoses and wires which must be disconnected



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Fig. Fig. 3: Any hoses which are not clamped may be grasped and pulled from the carburetor by hand

Model 2SE and E2SE Series Carburetors

WARNING
Before removing the carburetor allow the engine to cool completely to prevent ignition and possible fire from hot engine components such as the exhaust manifold.

  1. Disconnect the negative battery cable
  2.  
  3. Remove the air cleaner and its gasket.
  4.  
  5. Disconnect the fuel and vacuum lines from the carburetor.
  6.  


WARNING
Keep a rag handy to soak up any gasoline that might spill on any other components. Immediately dispose of the rag in a container approved for flammable or combustible refuse.

  1. Disconnect the electrical connectors for the choke and idle solenoid.
  2.  
  3. Disconnect the throttle linkage. Also disconnect the cruise control and transmission linkage, if equipped.
  4.  
  5. Remove the carburetor attaching nuts, gasket or insulator, and remove the carburetor.
  6.  

To install:
  1. Install new heat shield and insulator gaskets to the intake manifold.
  2.  
  3. Install the carburetor with the float bowl filled with gasoline to ease starting the engine later. Tighten nuts in a clockwise pattern to 45 inch lbs. (5 Nm). Once this is done, tighten nuts again in a clockwise pattern to 160 inch lbs. (18 Nm).
  4.  
  5. Reconnect the throttle linkage
  6.  
  7. Reconnect the electrical connectors for the choke and idle solenoid.
  8.  
  9. Reconnect the fuel and vacuum lines from the carburetor.
  10.  
  11. Reconnect the negative battery cable.
  12.  
  13. Check for fuel leaks by cranking the engine a little but not starting it. Be sure to check not only at the carburetor fuel line fitting but also at the fuel pump.
  14.  
  15. Install the air cleaner and its gasket.
  16.  



Click image to see an enlarged view

Fig. Fig. 4: If the hose is secured with a tension clamp, use pliers to move the clamp off past the bulge on the carburetor.



Click image to see an enlarged view

Fig. Fig. 5: Disconnect the linkage from the throttle lever. The accelerator cable is disconnected in the same manner

Model M2 Series Carburetors

WARNING
Before removing the carburetor allow the engine to cool completely to prevent ignition and possible fire from hot engine components such as the exhaust manifold.

  1. Disconnect the negative battery cable
  2.  
  3. Remove the air cleaner and its gasket.
  4.  
  5. Disconnect the fuel and vacuum lines from the carburetor.
  6.  


WARNING
Keep a rag handy to soak up any gasoline that might spill on any other components. Immediately dispose of the rag in a container approved for flammable or combustible refuse.

  1. Disconnect the electrical connectors for the choke and idle solenoid.
  2.  
  3. Disconnect the throttle linkage. Also disconnect the cruise control and transmission linkage, if equipped.
  4.  
  5. Remove the carburetor attaching bolts, gasket or insulator, and remove the carburetor.
  6.  

To install:
  1. Install new heat shield and insulator gaskets onto the intake manifold.
  2.  
  3. Install the carburetor with the float bowl filled with gasoline to ease starting the engine later. Tighten bolts in a clockwise pattern to 144 inch lbs. (16 Nm).
  4.  
  5. Reconnect the throttle linkage.
  6.  
  7. Reconnect the electrical connectors for the choke and idle solenoid.
  8.  
  9. Reconnect the fuel and vacuum lines from the carburetor.
  10.  
  11. Reconnect the negative battery cable.
  12.  
  13. Check for fuel leaks by cranking the engine a little but not starting it. Be sure to check not only at the carburetor fuel line fitting but also at the fuel pump.
  14.  
  15. Install the air cleaner and its gasket.
  16.  



Click image to see an enlarged view

Fig. Fig. 6: Disconnect the throttle return springs from the throttle lever



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Fig. Fig. 7: If equipped with an automatic transmission, disconnect the transmission throttle valve (detent) cable from the throttle lever



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Fig. Fig. 8: Disengage the electrical connectors from electric choke and/or solenoid on the carburetor

Model M4 Series Carburetors

WARNING
Before removing the carburetor allow the engine to cool completely to prevent ignition and possible fire from hot engine components such as the exhaust manifold.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and its gasket.
  4.  
  5. Disconnect the fuel and vacuum lines from the carburetor.
  6.  


WARNING
Keep a rag handy to soak up any gasoline that might spill on any other components. Immediately dispose of the rag in a container approved for flammable or combustible refuse.

  1. Disconnect the electrical connectors for the choke and idle solenoid.
  2.  
  3. Disconnect the throttle linkage. Also disconnect the cruise control and transmission linkage, if equipped.
  4.  
  5. Remove the carburetor attaching nuts and/or bolts, gasket or insulator, and remove the carburetor.
  6.  

To install:
  1. Install new heat shield and insulator gaskets to the intake manifold.
  2.  
  3. Install the carburetor with the float bowl filled with gasoline to ease starting the engine later. Tighten in a criss-cross pattern to 144 inch lbs. (16 Nm).
  4.  
  5. Reconnect the throttle linkage. Also reconnect the cruise and transmission linkage, if so equipped.
  6.  
  7. Reconnect the electrical connectors for the choke and idle solenoid.
  8.  
  9. Reconnect the fuel and vacuum lines from the carburetor.
  10.  
  11. Reconnect the negative battery cable.
  12.  
  13. Check for fuel leaks by cranking the engine a little but not starting it. Be sure to check not only at the carburetor fuel line fitting but also at the fuel pump.
  14.  
  15. Install the air cleaner and its gasket.
  16.  



Click image to see an enlarged view

Fig. Fig. 9: Loosen the carburetor retaining bolts either using a ratchet or a wrench



Click image to see an enlarged view

Fig. Fig. 10: At one end of most carburetors are 2 long retaining bolts



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Fig. Fig. 11: Shorter carburetor retaining bolts may be found at the base flange

Model E4 Series Carburetors


WARNING
Before removing the carburetor allow the engine to cool completely to prevent ignition and possible fire from hot engine components such as the exhaust manifold.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and its gasket.
  4.  
  5. Disconnect the fuel and vacuum lines from the carburetor.
  6.  


WARNING
Keep a rag handy to soak up any gasoline that might spill on any other components. Immediately dispose of the rag in a container approved for flammable or combustible refuse.

  1. Disconnect the electrical connectors for the choke and idle solenoid.
  2.  
  3. Disconnect the throttle linkage. Also disconnect the cruise control and transmission linkage, if equipped.
  4.  
  5. Remove the carburetor attaching bolts, gasket or insulator, and remove the carburetor.
  6.  

To install:
  1. Install new heat shield and insulator gaskets to the intake manifold.
  2.  
  3. Install the carburetor with the float bowl filled with gasoline to ease starting the engine later. Tighten short bolts to 11 ft. lbs. (15 Nm) and long bolts to 7 ft. lbs. (9 Nm).
  4.  
  5. Reconnect the throttle linkage. Also reconnect the cruise and transmission linkage if so equipped.
  6.  
  7. Reconnect the electrical connectors for the choke and idle solenoid.
  8.  
  9. Reconnect the fuel and vacuum lines from the carburetor.
  10.  
  11. Reconnect the negative battery cable.
  12.  
  13. Check for fuel leaks by cranking the engine a little but not starting it. Be sure to check not only at the carburetor fuel line fitting but also at the fuel pump.
  14.  
  15. Install the air cleaner and its gasket.
  16.  



Click image to see an enlarged view

Fig. Fig. 12: With the bolts removed carefully lift the carburetor from the intake manifold



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Fig. Fig. 13: Remove the gasket from the intake manifold



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Fig. Fig. 14: If the carburetor is to be removed for any length of time, use a rag or some paper towels to cover the intake manifold opening

 
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