COLD ENRICHMENT ROD (CER) ADJUSTMENT
The CER mechanism affects carburetor air/fuel mixtures throughout engine operation, cold and warm. Several adjustments are required. Although each adjustment affects a particular phase of operation, and a maladjustment can lead to a particular performance symptom, the adjustment procedure must be performed completely and in the following sequence.
If adjustment cannot be accomplished due to epoxy in the adjustment nut, a new service assembly must be installed.
- Remove the carburetor from the engine.
- Install a suitable dial indicator on the carburetor, as shown in the Fig. 3.
The CER adjustment specifications are listed on a tag attached to the carburetor above the choke cap, as shown in figure given.
- Remove the choke diaphragm cover and spring.
- Remove the choke cap.
- Compress the idle speed positioner where applicable and insert a 5/16-1/2 in. spacer between the positioner stem and the throttle lever contact paddle. Retain in this position with a rubber band. This will locate the fast idle pick-up lever away from the cam and allow the cam to rotate freely.
- Install Stator Cap T77L-9848-A or equivalent as a weight to rotate the bimetal lever counterclockwise and seat the CER.
- Position the dial indicator with the tip centered on the top surface of the CER. Zero the dial indicator, then raise the weight slightly and release to check for accurate zero.
This adjustment will be the reference for other adjustments. Make sure the dial indicator reading is accurate.
See Figures 1 and 2
The CVR/CER nuts have cylindrical projections above the threads which are filled with epoxy after final adjustment. To adjust, the existing parts must be removed and a new assembly installed.
- Remove the E-clip and hinge pin.
- Turn the CER adjusting nut counterclockwise until the nut disengages from the rod.
- Remove the CVR and replace with a new assembly.
- The unbroken rod must be in place first before further assembly. Install the assembly and tighten the CER adjusting nut to lower and locate into position. Connect the lever to the swivel.
- Install the hinge pin and E-clip.
The rod has an undercut designed to break. If breakage does occur, a new rod assembly must be installed. The upper body must be loosened to position the rod through the opening. Replace the upper body gasket as necessary.
See Figures 3 and 4
- Install the stator cap and rotate clockwise to index. The dial should indicate the tag specification for Run at 75°F (24°C) plus or minus 0.010 in.
- Adjust by turning the choke adjusting nut clockwise to increase or counterclockwise to decrease the height.
See Figure 5
- Remove the stator cap.
- Rotate the choke bimetal lever clockwise until the CER travel stop screw bottoms on the choke seal retainer (full travel). The dial should indicate the tag specification for Start at 0°F (18°C) plus or minus 0.005 in.
- Adjust by turning the CER travel stop screw with a 5/64 in. hex wrench. clockwise to decrease or counterclockwise to increase height.
See Figure 6
- Push in the diaphragm assembly. The dial should indicate the tag specification for Start at 75°F (24°C) plus or minus 0.020 in.
- Adjust by rotating the diaphragm assembly clockwise to decrease or counterclockwise to increase height.
See Figure 7
- Seat the CER again using the stator cap weight and check for zero dial indicator reading. Reset the zero position of the indicator, if required. Remove the stator cap weight.
- Depress the CVR until seated. The dial should indicate the tag specification for CVR plus or minus 0.10 in.
- Adjust by holding the CVR with a 3 / 8 in. wrench and turning the adjustment with a 3 / 32 in. hex wrench, clockwise to decrease or counterclockwise to increase height.
- Reinstall the original choke diaphragm cover with the original spring.
See Figures 8 and 9
- Apply vacuum to the choke diaphragm cover, or depress the choke diaphragm rod to the seated position.
- Rotate the choke bimetal lever clockwise until the choke shaft lever pin contacts the fast idle intermediate lever. The dial should indicate the tag specification for Run at 0°F plus or minus 0.005 in.
- If an adjustment is required, remove the choke diaphragm cover and install a new cover with the original spring. This is necessary because of the tamper-resistant material on the adjustment screw.
- Adjust by rotating the screw in the diaphragm housing with a 5 / 64 in. hex wrench, clockwise to increase or counterclockwise to decrease height.
- Apply sealing liquid on the adjustment screw to secure the adjustment.
- Install lead ball plug in the adjusting screw hole.
See Figure 10
- Position the fast idle pick-up lever on the second step of the fast idle cam against the shoulder of the high step.
- Install the stator cap and rotate clockwise until the fast idle pick-up lever contacts the fast idle cam adjusting screw. The dial should indicate specification 0.360 in. plus or minus 0.005 in.
- Adjust by rotating the fast idle cam adjusting screw.
- Remove the stator cap.
- Assemble the choke cap, gasket and retainer with breakaway screws.
- Remove the dial indicator and rubber band.
- Install the carburetor and adjust the idle speeds.
See Figure 11
- Remove the carburetor from the engine.
- Remove the expansion plug covering the venturi valve limiter adjustment screw (center punch until loose).
- Remove the (WOT) stop adjustment screw and spring, using a 5 / 32 in. Allen wrench.
- Hold the throttle plates wipe open, lightly push the venturi valve toward "close position" and check the gap between the valve and venturi opening wall. Set the closing gap specification at 0.39-0.41 in. (9.91-10.41mm).
- Using a 5 / 64 in. Allen wrench, turn the venturi valve limiter adjustment screw (on the venturi valve arm) to set the closing gap to specification.
- Install the throttle (WOT) stop adjustment screw and spring, using a 5 / 32 in. Allen wrench.
- Lightly push the venturi valve "wide open to stop" and check the gap between the valve and air horn wall. This "maximum opening specification" is 0.99-1.01 in. (25.15-25.65mm).
- Turn the throttle (WOT) stop adjustment screw until the maximum opening is to specification.
- Install a new expansion plug and install the carburetor on the engine.
See Figures 12 through 16
The variable venturi carburetor is very insensitive to float level settings. The factory setting does not change with time and usage. Adjusting the float level setting will not correct any typical start/drive problems.
- Remove the carburetor.
- Remove the upper body assembly and the upper body gasket.
- If necessary, fabricate a gauge to the specified dimension.
- With the upper body inverted, place the float level gauge on the cast surface of the upper body and measure the vertical distance from the cast surface of the upper body and the bottom of the float.
- The float level specification is 1.010-1.070 in. (25.66-27.17mm).
- To adjust, bend the float operating lever away from the fuel inlet needle to decrease the setting and toward the needle to increase the setting.
- Check and/or adjust the float drop.
See Figures 17 and 18
- If necessary, fabricate a gauge to 1.430-1.490 in. (36.33-37.84mm).
- With the carburetor upper body assembly held in an upright position, place the gauge against the cast surface of the upper body and measure the vertical distance between the cast surface of the upper body and the bottom of the float.
- The float drop specification is 1.430-1.490 in. (36.33-37.84mm).
- To adjust, bend the stop tab on the float lever away from the hinge pin to increase the setting and toward the hinge pin to decrease the setting.
- Install a new upper body gasket and install the upper body assembly.
See Figure 19
REMOVAL & INSTALLATION
In many instances, flooding, stumble on acceleration, and other performance complaints are caused by the presence of dirt, water or other foreign material in the carburetor. To aid in complaint diagnosis, the carburetor should be carefully removed from the engine without removing the fuel from the bowl. The contents of the bowl can then be examined for contamination as the carburetor is disassembled.
- Disconnect the negative battery cable. Remove the air cleaner.
- Remove the throttle cable and transmission kickdown levers from the throttle lever. Tag and detach all vacuum lines, emission hoses, and electrical connections.
- Using a backup wrench on the carburetor inlet nut, slowly disconnect the fuel line from the carburetor.
- Remove the carburetor mounting nuts; then remove the carburetor. Remove the carburetor mounting gasket spacer, if equipped, and lower gasket from the intake manifold.
- Clean the gasket mounting surfaces of the spacer and carburetor. Place the spacer between 2 new gaskets and place the spacer and gaskets on the intake manifold. Position the carburetor on the spacer and gasket.
- Install the spark and EGR vacuum lines and fuel fitting before bolting the carburetor in place. Install the carburetor mounting nuts and hand tighten them. Then, alternately tighten each nut in a crisscross pattern to 12-15 ft. lbs. (16-20 Nm).
- Connect the throttle cable and all emission and vacuum lines. Observe the color coded vacuum line connections on the carburetor.
- Run the engine and adjust the idle speeds. Check for fuel leaks. Adjust the throttle valve lever.