Carburetor - Carter Bbd 2-bbl Dodge Diplomat I

COMPONENT TESTING

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

APPLICATION

(CARTER) CARBURETOR NO.

IDENTIFICATION

Carter carburetor number is stamped on a tag attached to carburetor by 1 air horn screw. (Scheme 22)

Carter Model BBD Carburetor I.D. Tag. Scheme 22

DESCRIPTION

The model BBD carburetor is a 2-barrel downdraft type, incorporating 3 basic fuel metering systems. The idle system provides mixture for idle and low speed operation. The accelerator pump system provides additional fuel for acceleration. The main metering system provides a more economical mixture for normal driving.

The carburetor is also equipped with a fuel inlet system which supplies a constant amount of fuel to provide sufficient fuel to the metering circuits for all engine operating conditions. The electrically assisted choke system provides temporary enrichment of the air/fuel mixture to aid in starting and running a cold engine.

Carburetors are equipped with a duty cycle solenoid that is controlled by a Spark Control Computer. The solenoid is used to alter the main air/fuel mixture, in response to commands from an oxygen sensor and is located on rear of carburetor main body.

The BBD carburetor is equipped with idle speed control systems which maintain idle speed on vehicles equipped with A/C and other accessories.

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article, see appropriate TUNE-UP article.

Scheme 23

1. Remove air horn. Turn main body upside down. Catch accelerator pump check ball as it falls out. Hold float pin retainer in with finger. Weight of float should be closing float needle. (Scheme 23) (Scheme 23): Float Level Adjustment Bend tang to adjust.
2. Place a straightedge across main body. Measure float level specified clearance between straightedge and crown of each float.
3. To adjust, bend float tang to obtain specified clearance. Float tang is portion of float that contacts end of float needle valve.

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 positions piston in a "mean" or centered position.

Scheme 24

1. Remove step-up piston cover plate and gasket. Remove lifter lock screw and piston.
2. Measure piston gap (Scheme 24) If not to specifications, adjust Allen head screw on top of piston. (Scheme 24): Vacuum Step-Up Piston Gap Qualification This adjustment positions piston in a "mean" or centered position.
3. Turning screw clockwise makes mixture richer. Turning screw counterclockwise makes mixture leaner.

VACUUM STEP-UP PISTON

Note. Perform Vacuum Step-Up Piston Gap Qualification adjustment first.

1. With vacuum piston installed, back off curb idle speed screw until throttle valves are seated. Count number of turns required to seat throttle valves.
2. Loosen lifter lock screw. Fully depress piston in bore. At same time, hold pressure against rod lifter tab. Tighten lifter lock screw.
3. Release lifter and piston. Adjust accelerator pump. Readjust curb idle speed screw to its original position.

Vacuum Step-Up Piston Adjusment Make adjustment with throttle valves completely closed. Scheme 25

Scheme 26

1. Remove step-up piston cover plate and gasket. Back off curb idle speed screw until throttle valves are seated. Count number of turns required to seat throttle valves. Fast idle cam must be in open choke position. (Scheme 26) (Scheme 26): Accelerator Pump Stroke Adjustment Adjust with throttle valves fully closed.
2. Turn curb idle screw clockwise until it just touches stop. Continue 2 more complete turns.
3. Some models may have 2 holes in accelerator pump arm. If so, make sure accelerator pump "S" link is in outer hole.
4. Measure distance between surface of air horn and top of accelerator pump shaft. If adjustment is needed, loosen pump arm adjusting lock screw and turn sleeve to adjust pump travel. When correct measurement is obtained, tighten lock screw.
5. Install step-up piston cover plate and gasket. Readjust curb idle speed screw to its original position.

Note. If the accelerator pump adjustment is changed, the Bowl Vent Adjustment must be reset.

MECHANICAL BOWL VENT VALVE ADJUSTMENT

Note. This is not a precise adjustment. The purpose of this adjustment is to ensure that bowl vent is open at idle and closed at greater throttle openings. It may be performed on or off the vehicle.

Carburetors are equipped with a bowl vent solenoid which allows float vapors to flow to carbon canister only when engine is stopped. There is no vent adjustment necessary on these models.

Scheme 27

1. Place fast idle speed screw on 2nd step of fast idle cam. (Scheme 27) (Scheme 27): Fast Idle Cam Position Adjustment Adjust by bending fast idle cam rod.
2. Hold choke valve toward closed position. Measure fast idle cam specified clearance between upper edge of choke valve and air horn wall.
3. If clearance is not to specification, adjust by bending fast idle cam rod. Bend rod down to increase clearance and up to decrease clearance.

Scheme 28

1. Place fast idle speed screw on highest step of fast idle cam. (Scheme 28) (Scheme 28): Choke Vacuum Break Adjustment Bend vacuum break diaphragm rod to adjust.
2. Apply an outside vacuum source of at least 19 in. hg to choke vacuum break diaphragm. Apply enough closing force on choke valve to compress spring on diaphragm stem.
3. Measure choke vacuum break specified clearance between upper edge of choke valve and air horn wall. To adjust, bend vacuum break diaphragm rod.

Scheme 29

1. Open throttle valves wide open. Apply light closing pressure to choke valve. (Scheme 29) (Scheme 29): Choke Unloader Adjustment Bend choke unloader tang to adjust.
2. Measure specified choke unloader clearance between upper edge of choke valve and air horn wall.
3. To adjust, bend choke unloader tang. Make sure linkage is free and does not bind after making adjustment.

AUTOMATIC CHOKE

Automatic choke adjustment is made by removing choke housing retaining screws and turning housing to correct index or notch on choke housing. Refer to Specification Table for correct position for each carburetor.

IDLE MIXTURE SCREW PLUG

1. Remove air cleaner assembly, vacuum hoses and throttle linkage from carburetor. Locate and center punch a mark on side surface of mixture screw housing, 5/16" from front end of housing in the center of both mixture screw housings.
2. Using 3/16" drill bit, drill at 90° angle to mixture screw housing through outer surface of housing. Concealment plug should drop out. If not, use small drift to remove plug. CAUTION: DO NOT allow drift to contact mixture screw.
3. Reinstall linkage, vacuum hoses and air cleaner assembly. Perform propane idle mixture RPM adjustment. Reinstall concealment plug.

Scheme 30

1. Place carburetor on stand and remove stepper motor or duty cycle solenoid. Remove retaining clip from accelerator pump arm link and remove link.
2. Remove cover plate from over step-up piston and remove gasket. Remove locks and screws from accelerator pump arm and vacuum piston rod lifter. Slide pump lever out of air horn.
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 end of choke shaft. Remove choke vacuum break diaphragm. Remove fast idle cam retaining screw and remove fast idle cam, linkage and clip.
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 main metering jets.
7. Remove venturi cluster screws. Lift cluster and gaskets away from main body. Discard gaskets. DO NOT remove idle orifice tubes or main vent tubes from cluster. They may 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. (Scheme 30): Exploded View of Carter Model BBD 2-Barrel Carburetor
9. Turn idle limiter caps to stop. Remove plastic caps from idle mixture screws. Be sure to count number of turns it takes to set screws for reassembly reference. Remove screws and springs.
10. 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

1. DO NOT clean rubber, plastic parts or diaphragms, solenoid assemblies or pump plunger in solvent.
2. DO NOT use wire, drill bit or hard parts to clean passages in carburetors.
3. Inspect all parts for wear, cracks, nicks or burrs, uneven gasket sealing surfaces or warpage.
4. Check for stripped threads, and excessive wear on throttle shafts. Replace throttle body assembly if shafts are worn.

REASSEMBLY

Note. Use new gaskets and seals. Make sure new gaskets fit correctly and all holes are punched through and correctly located.

To reassemble carburetor, reverse disassembly procedures while noting the following

Accelerator Pump Assembly

1. Check operation as follows. Pour clean gasoline into carburetor bowl (1/2" deep). Operate pump plunger several times to fill cylinder and expel all air.
2. Using a small brass rod, hold discharge check ball down on its seat. Raise plunger and press downward. No fuel should be emitted from either intake or discharge passage. If fuel does escape from passages, check if ball seat is damaged or dirty.
3. Clean check ball seat and retest. If leakage is still present, attempt to form a new ball seat. To form a new seat, install discharge check ball and place a piece of drill rod on top of check ball. Lightly tap drill rod with a mallet to form a new seat.
4. Remove and discard check ball and install a new one. Retest as previously described. If service does not correct problems, replace carburetor.

Step-Up Piston & Rod Assembly

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

Locations of Large & Small Check Balls. Scheme 31

SPECIFICATIONS

CARBURETOR ADJUSTMENT SPECIFICATIONS (1)