Carburetor - Carter Bbd 2-bbl Jeep Wagoneer SJ

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

APPLICATION

JEEP (CARTER) CARBURETOR NO.

IDENTIFICATION

Carter carburetors are identified by a code number and build date. Both numbers are stamped on a tag attached to carburetor by an air horn screw. Each carburetor build month is coded alphabetically beginning with letter "A" (for January), and ending with "M" (for December). Letter "I" is not used.

Second number on tag is year in which carburetor was built. Third and fourth numbers are for build day. There may be a revision letter following build day numbers if needed.

Carter Model BBD I.D. Tag. Scheme 1

DESCRIPTION

The Carter model BBD is a 2-barrel downdraft carburetor. The BBD has 4 basic fuel metering systems: float (fuel inlet) system; idle (low speed) system; accelerator pump system; and the main (high speed) system.

The float system maintains fuel level. The idle system is used for idle and initial part-throttle operation. The main system is used for part-throttle and cruising operation. The pump system provides additional fuel for acceleration.

An electric choke with a choke diaphragm is used. The carburetor is equipped with a stepper motor to control air flow in metered air bleeds in the main fuel metering circuit. All Jeep vehicles use a vacuum solenoid called a Solevac to keep idle speed constant when load is placed on engine.

ADJUSTMENT

Note. For all on vehicle adjustments, see TUNE-UP SERVICE PROCEDURES.

FLOAT LEVEL (BENCH ADJUSTMENT)

1. Remove air horn. Hold float lip gently against needle. (Scheme 2)
2. Using a straightedge, place across float bowl to measure float level. If adjustment is needed, release float and then bend float tip to obtain correct clearance. Reinstall air horn.

Note. To avoid damaging synthetic rubber tip, do not bend lip while float is resting against needle.

Adjusting Float Level on Jeep Models Hold finger against fulcrum pin retainer. Scheme 2

VACUUM STEP-UP PISTON GAP QUALIFICATION

Note. This adjustment is required if step-up piston is removed or if piston lifter position is changed on actuating rod. This adjustment (qualification) places piston in a centered "mean" position.

1. Remove step-up piston cover plate and gasket. Remove lifter lock screw and remove piston step-up assembly.
2. Measure piston gap. (Scheme 3) If not to specification, adjust by turning Allen head screw on top of piston.
3. Record number of turns and direction to obtain proper dimension. This must be reset to its original position after vacuum step-up piston adjustment has been made.

Vacuum Step-Up Piston Gap Qualification Record number of turns and direction. Scheme 3

VACUUM STEP-UP PISTON ADJUSTMENT

Note. Perform Vacuum Step-Up Piston Gap Qualification adjustment before adjusting vacuum step-up piston.

Scheme 4

1. With vacuum piston installed, back off idle speed screw until throttle valves are completely closed. Count number of turns so screw can be returned to its original position. (Scheme 4) (Scheme 4): Adjusting Step-Up Piston If this adjustment is changed, the step-up piston must be re-qualified
2. Fully depress step-up piston while holding moderate pressure on rod lifter tab. While in this position, tighten rod lifter lock screw.
3. Release piston and rod lifter. Return idle speed set screw to its original position.
4. Reset Allen head calibration screw on top of step-up piston to its original position as recorded under Vacuum Step-Up Piston Gap Qualification. If this adjustment is changed, the step-up piston must be requalified.

Scheme 5

1. Remove step-up piston cover plate and gasket. Back off curb idle screw to fully close throttle valves. Fast idle cam must be in open position. On Chrysler Corp. vehicles, if pump arm has 2 holes ensure pump "S" link is in outer hole. Open choke valve so that fast idle cam allows throttle valves to seat. (Scheme 5) (Scheme 5): Adjusting Accelerator Pump Stroke Fast idle cam must be in open position.
2. Turn curb idle screw until it just touches stop. Continue 2 more complete turns. Measure distance between surface of air horn and top of accelerator pump shaft.
3. If adjustment is required, loosen pump arm adjusting lock screw and turn sleeve to adjust pump travel. When correct measurement is obtained, tighten lock screw. Install step-up piston cover plate and gasket.

AUTOMATIC CHOKE

Note. Normally, no readjustment is necessary from factory setting. Perform adjustment only after a major overhaul.

1. Loosen choke thermostat cover retaining screws.
2. Rotate cover in "Rich" or "Lean" direction to align reference mark on cover with specified scale graduation on choke housing. Tighten retaining screws.

VACUUM KICK (INITIAL CHOKE VALVE CLEARANCE)

Note. All carburetors incorporate tamper-proof choke, choke pull-off, and idle adjusting screws. Adjustments given are for after major overhaul, or if carburetor components have been damaged.

Scheme 6

1. On Jeep vehicles, grind off torque-head screw heads. Remove remaining portions of screws by turning counterclockwise with locking pliers. Turn choke cover 1/4 turn rich. Retain in position with 1 straight slot screw.
2. Open throttle valve slightly to place fast idle screw on high step of cam. (Scheme 6): Adjusting Choke Diaphragm (Initial Choke Valve Clearance) Place fast idle screw on high step of cam.
3. On Jeep vehicles, remove straight slot screw and adjust cover index to specified notch. Install replacement torque-head screws.

FAST IDLE CAM POSITION

Note. All carburetors incorporate tamper-proof choke, choke pull-off, and idle adjusting screws. The following adjustments are for after major carburetor overhaul, or if carburetor components are damaged.

Scheme 7

1. On Jeep vehicles, remove torque-head screws and position choke cover 1/4 turn rich. Retain with 1 straight-slot screw to hold choke cover in position. On all models, place fast idle adjusting screw on 2nd step of fast idle cam. (Scheme 7) (Scheme 7): Adjusting Fast Idle Cam Position Place fast idle speed adjusting screw on 2nd step of fast idle cam.
2. With specified drill or pin gauge, measure clearance between upper edge of choke valve and air horn wall. To adjust, bend fast idle connecting rod down to increase measurement or up to decrease measurement.
3. On Jeep vehicles, loosen housing cover screw and reset choke to specified index position. Install replacement torque-head screws.

Scheme 8

1. Hold throttle valves wide open. Apply light closing pressure to choke valve lever. (Scheme 8) (Scheme 8): Adjusting Choke Unloader Throttle valves should be in wide open position.
2. Measure choke unloader specified clearance between upper edge of choke valve and air horn wall. Clearance can be checked using a specified drill or pin gauge.
3. To adjust, bend choke unloader tang. Make sure tang does not interfere with other components after it is adjusted.

All Models

1. Place carburetor on a repair stand, and remove stepper motor if equipped. Remove retaining clip from accelerator pump arm link and remove link.
2. Remove cover and gasket from top of air horn. Remove screws and locks from accelerator pump arm and vacuum piston rod lifter. Slide pump lever out of air horn. Remove pump arm and rod lifter.
3. Lift vacuum piston and step-up rods up and out of air horn as an assembly. Remove the vacuum piston spring. Remove choke vacuum diaphragm hose. Disconnect clips and remove link from choke housing lever and choke lever.
4. Remove screw and lever from choke shaft. Remove choke diaphragm, linkage, and bracket assembly. Remove fast idle cam retaining screw. Remove fast idle cam, choke link, and clip. On Jeep vehicles, grind heads off of torque-head screws. Remove choke cover assembly and housing from throttle body. Remove remaining portion of screws with locking pliers.
5. Remove screws securing air horn and lift air horn up and away from main body. Discard gasket. Turn air horn upside-down and compress accelerator pump drive spring. Remove "S" link from pump shaft. Remove pump assembly.
6. Remove fuel inlet needle valve, seat and gasket from main body. Carefully lift out float fulcrum pin retainer and baffle. Lift out floats and fulcrum pin. Remove the main metering jets.
7. Remove venturi cluster screws. Lift cluster and gaskets away from main body and discard gaskets. DO NOT remove idle orifice tubes or main vent tubes from cluster as they can be cleaned with solvent and dried with compressed air while assembled.
8. Turn carburetor upside-down and catch accelerator pump discharge and intake check balls as they fall out.
9. On Jeep vehicles, turn idle limiter caps to stop. Remove plastic caps from idle air mixture screws. Be sure to count number of turns it takes to seat screws to ease reassembly adjustment.
10. On all vehicles, remove screws and springs from throttle body.
11. Remove screws and separate throttle body from main body. Discard gasket. Check choke plate in air horn for freedom of movement. If any sticking or binding is evident, clean thoroughly.

CLEANING & INSPECTION

Note. DO NOT apply compressed air to diaphragm. DO NOT use wire or drill to clean jets or passageways.

1. Use a regular carburetor cleaning solution. Soak components long enough to thoroughly clean all surfaces and passages of foreign matter.
2. DO NOT soak any components containing rubber, leather or plastic.
3. Remove any residue after cleaning by rinsing components in a suitable solvent.
4. Blow out all passages with dry compressed air.

REASSEMBLY

Use all new gaskets and reverse disassembly procedures while noting the following

Idle Mixture Screw Installation

1. Install idle mixture screws and springs in body. Tapered portion must be straight and smooth. If tapered portion is grooved or ridged, use a new screw. DO NOT use a screwdriver for installation.
2. Turn screws lightly against their seats with fingers. Back off number of turns counted at disassembly (Jeep). On Jeep vehicles install new plastic caps with tab against stop.

Accelerator Pump Check Ball Installation

Accelerator pump intake and discharge check balls are different sizes. Make sure large check ball is installed in float bowl. (Scheme 10)

Scheme 9

Scheme 10

Scheme 11

1. Check operation as follows: Pour clean unleaded gasoline into carburetor bowl approximately 1/2" deep. Operate accelerator pump plunger several times to expel air from pump passage. Using a small brass rod, hold discharge check ball down firmly on its seat. (Scheme 11) (Scheme 9): Exploded View of Carter Model BBD 2-Barrel Carburetor (Scheme 10): Installing Accelerator Pump Intake and Discharge Check Balls Large check ball is installed in float bowl. (Scheme 11): Testing Accelerator Pump Intake and Discharge Hold discharge check ball down on its seat.
2. Again raise plunger and press downward. No fuel should be emitted from either intake or discharge passage. If fuel does escape from either passage, check that ball seat is not damaged or dirty. Clean passages and retest.
3. If leakage is still present, attempt to form a new seat. This is accomplished by installing a discharge check ball in leaking seat. Place a piece of drill rod on top of check ball and tap it lightly with a hammer to form a new seat. Remove check ball and discard. Install a new check ball and retest as described above. If service does not correct problem, carburetor replacement is necessary.

Step-Up Piston & Rod Assembly

Be sure step-up rods move freely each side of vertical position. Carefully guide step-up rods into main metering jets.

SPECIFICATIONS

CARBURETOR ADJUSTMENT SPECIFICATIONS