- Place the transmission in P or N .
- Allow the engine to operate until normal operating temperature is reached.
- Turn all accessories off.
Check/adjust curb idle rpm:
- On non-air conditioning equipped vehicles, adjust the saddle bracket adjusting screw.
- On air conditioning equipped vehicles, adjust the hex head screw protruding from the rear of the TSP housing.
- Slightly rev the engine momentarily. Recheck the curb idle and readjust, if required.
See Figure 1
- Place the transmission in Neutral or Park position.
- Bring the engine to normal operating condition.
- Disconnect the vacuum hose at the EGR valve and plug.
- Place the fast idle cam adjustment on the specified step of the fast idle cam. Check and adjust the fast idle rpm to specification.
- Rev the engine momentarily, place the fast idle on the specified step and then recheck the fast idles RPM.
- Remove the plug from the EGR vacuum hose, then reconnect.
- Set the parking brake and block the drive wheels.
- Connect a tachometer (Rotunda 20362 or equivalent).
- If equipped with a Hot Idle Compensator (HIC), insure that it remains in closed position throughout the test. Idle the vehicle on the kickdown step of the fast idle cam for 3 minutes to ensure the HIC valve is closed.
- Disconnect the fuel evaporative purge return hose at the engine and air cleaner, if equipped. Plug the connections.
- Disconnect the flexible fresh air tube from the air cleaner duct or adaptor. Using a propane enrichment tool (Rotunda T75L-9600 or equivalent), insert the tool hose approximately 3 / 4 of the way into the duct or fresh air tube. If necessary, secure the hose with tape.
On vehicles equipped with thermactor system, revise the dump valve vacuum hoses as follows:
- For dump valves with 2 vacuum fittings, disconnect and plug the hoses.
- For dump valves with 1 fitting or combination air bypass/air control valve, remove the hose at the dump valve and plug it. Connect a slave hose from the dump valve vacuum fitting to an intake manifold vacuum fitting.
Leave all vacuum signal hoses attached to the air cleaner assembly when relocating the assembly to perform carburetor adjustments. The air cleaner assembly must be in place, however, when measuring engine speeds.
- Verify the ignition timing and curb idle is set to specifications.
- Remove the PCV valve from the grommet and allow it to draw underhood air during the idle mixture check. Locate the crankcase vent hose and disconnect it at the air cleaner, allowing the in-line fixed orifice to vent to underhood air.
- With the transmission in N , run the engine at approximately 2500 rpm for 15 seconds before each mixture check.
- Gradually open the propane tool valve and watch for engine speed gain, if any, on the tachometer. When the engine speed reaches a maximum and then begins to drop off, note the amount of speed gain. The propane cartridge must be in vertical position.
If the engine speed will not drop off, check the propane cartridge gas supply. If necessary, repeat Steps 9 and 10 with a new cartridge. If the measured speed gain is 0 rpm (no rpm rise) and the minimum speed gain specification is 0 rpm, go to Step 13.
- If the measured speed gain is higher than the speed gain specification, turn the mixture screws counter clockwise (rich) in equal amounts while simultaneously repeating the mixture adjustment, until the measured speed rise meets the reset rpm specification.
- Reinstall the PCV valve in the grommet and adjust the curb idle.
- Reinstall the tamper resistant feature.
See Figure 2
- Remove the air cleaner assembly.
- Set the throttle on the stop step of the fast idle cam.
- Noting the position of the choke housing cap, loosen the retaining screws and rotate the cap 90° in the rich (closing) direction.
- Activate the pulldown motor by manually forcing the pulldown control diaphragm link in the direction of applied vacuum or by applying vacuum to the external vacuum tube.
- Using a drill gauge of the specified diameter, measure the clearance between the choke plate and the center of the air horn wall nearest the fuel bowl.
- To adjust, reset the diaphragm stop on the end of the choke pulldown diaphragm.
- After adjusting, reset the choke housing cap to the specified notch. Check and reset fast idle speed, if necessary. Install the air cleaner.
See Figures 3 and 4
This preliminary setting of the float level adjustment must be done with the carburetor removed from the engine.
- Remove the air horn and see that the float is raised and the fuel inlet needle is seated. Check the distance between the top surface of the main body (with the gasket removed) and the top surface of the float. Depress the float tab to seat the fuel inlet needle. Take a measurement near the center of the float, at a point 1 / 8 in. (3mm) from the free end. If you are using a prefabricated float gauge, place the gauge in the corner of the enlarged end section of the fuel bowl. The gauge should touch the float near the end, but not on the end radius.
- If necessary, bend the tab on the end of the float to bring the setting within the specified limits.
See Figure 5
- Bring the engine to its normal operating temperature, park the car on as nearly level a surface as possible, and stop the engine.
- Remove the air cleaner assembly from the carburetor.
- Remove the air horn retaining screws and the carburetor identification tag. Leave the air horn and gasket in position on the carburetor main body. Start the engine, let it idle for several minutes, rotate the air horn out of the way, and remove the gasket to provide access to the float assembly.
- With the engine idling, use a standard depth scale to measure the vertical distance from the top machined surface of the carburetor main body to the level of the fuel in the fuel bowl. This measurement must be made at least 1 / 4 in. (6mm) away from any vertical surface in order to assure an accurate reading.
- Stop the engine before making any adjustment to the float level. Adjustment is accomplished by bending the float tab (with contacts the fuel inlet valve) up or down as required to raise or lower the fuel level. After making an adjustment, start the engine, and allow it to idle for several minutes before repeating the fuel level check. Repeat as necessary until the proper fuel level is attained.
- Reinstall the air horn with a new gasket and secure it with the screw. Include the installation of the identification tag in its proper location.
- Check the idle speed, fuel mixture, and dashpot adjustments. Install the air cleaner assembly.
By rotating the spring housing of the automatic choke, the reaction of the choke to engine temperature can be controlled. To adjust, remove the air cleaner assembly, loosen the thermostatic spring housing retaining screws and set the spring housing to the specified index mark. The marks are shown in the accompanying illustration. After adjusting the setting, tighten the retaining screws and replace the air cleaner assembly to the carburetor.ACCELERATOR PUMP STROKE ADJUSTMENT
See Figure 6
In order to keep the exhaust emission level of the engine within the specified limits, the accelerating pump stroke has been preset at the factory. The additional holes are provided for differing engine-transmission-body applications only. The primary throttle shaft lever (overtravel lever) has four holes to control the pump stroke. The accelerating pump operating rod should be in the overtravel lever hole number listed in the Carburetor Specifications chart, and in the inboard hole (hole closest to the pump plunger) in the accelerating pump link. If the pump stroke has been changed from the specified settings, use the following procedure to correct the stroke.
- Release the operating rod from the retaining clip by pressing the tab end of the clip toward the rod while pressing the rod away from the clip until it disengages.
- Position the clip over the specified hole (see Carburetor Specifications chart) in the overtravel lever. Press the ends of the clip together and insert the operating rod through the clip and the overtravel lever. Release the clip to engage the rod.
Having made sure that the engine idle speed and mixture are correct and that the engine is at normal operating temperature, loosen the anti-stall dashpot locking nut (see accompanying illustration). With the throttle held closed, depress the plunger with a screwdriver blade and measure the clearance between the throttle lever and the plunger tip. If the clearance is not as specified in the Carburetor Specifications chart, turn the dashpot until the proper clearance is obtained between the throttle lever and the plunger tip. After tightening the locking nut, recheck the adjustment.KICKER SET SPEED
- Place the transmission in the Neutral or Park position.
- Bring the engine to the normal operating temperature.
- Place the A/C-heater selector in the OFF position.
- Disconnect and plug the vacuum hose at the VOTM kicker.
- Connect the external vacuum source providing a minimum of 33.7 kPA (10 in-Hg) to the VOTM kicker.
- Place the transmission selector in the specified position.
- Check and adjust the VOTM kicker on the rpm, if the adjustment is required. Adjust the VOTM saddle bracket adjustment screw.
- Remove the external vacuum source, remove the plug from the VOTM kicker hose and reconnect.
- Reset the curb idle.
See Figures 7, 8 and 9
All carbureted models use an electrically assisted choke to reduce exhaust emissions of carbon monoxide during warm-up. The system consists of a choke cap, a thermostatic spring, a bimetal sensing disc (switch) and a ceramic positive temperature coefficient (PTC) heater.
The choke is powered from the center tap of the alternator, so that current is constantly applied to the temperature sensing disc. The system is grounded through the carburetor body. At temperatures below approximately 60°F (16°C), the switch is open and no current is supplied to the ceramic heater, thereby resulting in normal unassisted thermostatic spring choke action. When the temperature rises above 60°F (16°C), the temperature sensing disc closes and current is supplied to the heater, which in turn, acts on the thermostatic spring. Once the heater starts, it causes the thermostatic spring to pull the choke plate(s) open within 1 1 / 2 minutes, which is sooner than it would open if non-assisted.
- Detach the electrical lead from the choke cap.
- Use a jumper lead to connect the terminal on the choke cap and the wire terminal, so that the electrical circuit is still completed.
- Start the engine.
- Hook up a test light between the connector on the choke lead and ground.
- The test light should glow. If it does not, current is not being supplied to the electrically assisted choke.
- Connect the test light between the terminal on the alternator and the terminal on the choke cap. If the light now glows, replace the lead, since it is not passing current to the choke assist.
- If the light still does not glow, the fault lies somewhere in the electrical system. Check the system out. If the electrically assisted choke receives power but still does not appear to be functioning properly, reconnect the choke lead and proceed with the rest of the test.
- Tape the bulb end of the thermometer to the metallic portion of the choke housing.
- If the electrically assisted choke operates below 55°F (13°C), it is defective and must be replaced.
- Allow the engine to warm up to 80-100°F (27-38°C); at these temperatures the choke should operate for about 1 1 / 2 minutes.
- If it does not operate for this length of time, check the bimetallic spring to see if it is connected to the tang on the choke lever.
- If the spring is connected and the choke is not operating properly, replace the cap assembly.
See Figure 10
Efficient carburetion depends greatly on careful cleaning and inspection during overhaul, since dirt, gum, water, or varnish in or on the carburetor parts are often responsible for poor performance.
Overhaul your carburetor in a clean, dust free area. Carefully disassemble the carburetor, referring often to the exploded views. Keep all similar and look-alike parts segregated during the disassembly and cleaning to avoid accidental interchange during assembly. Make a note of all jet sizes.
When the carburetor is disassembled, wash all parts (except diaphragms, electric choke units, pump plunger, and any other plastic, leather, fiber, or rubber parts) in clean carburetor solvent. Do not leave parts in the solvent any longer than is necessary to sufficiently loosen the deposits. Excessive cleaning may remove the special finish from the float bowl and choke valve bodies, leaving these parts unfit for service. Rinse all parts in clean solvent and blow them dry with compressed air or allow them to air dry. Wipe clean all cork, plastic, leather, and fiber parts with a clean, lint-free cloth.
Blow out all passages and jets with compressed air and be sure that there are no restrictions or blockages. never use wire of similar tools to clean jets, fuel passages, or air bleeds. Clean all jets and valves separately to avoid accidental interchange.
Check all parts for wear or damage. If wear or damage is found, replace the defective parts. Especially check the following:
- Check the float needle and seat for wear. If wear is found, replace the complete assembly.
- Check the float hinge pin for wear and the float(s) for dents or distortion. Replace the float if fuel has leaked into it.
- Check the throttle and choke shaft bores for wear or an out-of-round condition. Damage or wear to the throttle arm, shaft, or shaft bore will often require replacement of the throttle body. These parts require a close tolerance of fit; wear may allow air linkage, which could affect starting and idling.
Throttle shafts and bushings are not included in overhaul kits. They can be purchased separately.
- Inspect the idle mixture adjusting needles for burrs for grooves. Any such condition requires replacement of the needle, since you will not be able to obtain a satisfactory idle.
- Test the accelerator pump check valves. They should pass air one way but not the other. Test for proper seating by blowing and sucking on the valve. Replace the valve is necessary. If the valve is satisfactory, wash the valve again to remove breath moisture.
- Check the bowl cover for warped surfaces with a straightedge.
- Closely inspect the valves and seats for wear and damage, replacing as necessary.
- After the carburetor is assembled, check the choke valve for freedom of operation.
Carburetor overhaul kits are recommended for each overhaul. These kits contain all gaskets and new parts to replace those which deteriorate most rapidly. Failure to replace all parts supplied with the kit (especially gaskets) can result in poor performance later.
Some carburetor manufacturers supply overhaul kits of three basic types: minor repair; major repair; and gasket kits. Basically, they contain the following:Minor Repair Kits:
Major Repair Kits:
After cleaning and checking all components, reassemble the carburetor, using new parts and referring to he exploded view. When reassembling, make sure that all screws and jets are tight in their seats, but do not overtighten as the tops will be distorted. Tighten all screws gradually, in rotation. Do not tighten needle valves into their seats; uneven jetting will result. Always use new gaskets. Be sure to adjust the float level when reassembling.Motorcraft 2150
See Figures 11, 12 and 13
- Remove the air cleaner anchor screw.
- Remove the automatic choke control rod retainer.
- Remove the airhorn attaching screws, lockwashers and the carburetor identification tag. Remove the airhorn and the airhorn gasket.
- Remove the choke control rod by loosening the screw that secures the choke shaft lever to the choke shaft. Remove the rod from the airhorn. Slide the plastic dust seal out of the airhorn.
- Remove the staking marks on the choke plate attaching screws and remove the screws. Remove the choke plate by sliding it out of the shaft from the top of the airhorn. Remove any burrs around screw holes prior to removing the choke shaft. Slide the choke shaft out of the airhorn.
- Remove the two attaching screws on the choke pulldown diaphragm assembly from the bracket, disconnect the vacuum supply tube, disconnect the E-clip at the rod and remove the pulldown diaphragm.
- Remove the fast idle cam retainer.
- Center punch the choke cap retaining screw heads and using a 1 / 4 in. (6mm) drill, drill the screw heads deep enough to remove the retainer from the choke cap. Remove the remaining portion of the choke cap screws with small locking pliers.
- Remove the choke housing assembly retaining screws. Remove the choke housing assembly, gasket and the fast idle cam and rod from the fast idle cam lever.
- Remove the choke lever retaining screw and washer. Disconnect the choke control rod from the choke lever. Remove the choke lever and fast idle cam lever from the choke housing.
- With a screwdriver, pry the float shaft retainer from the fuel inlet seat. Remove the float, float shaft retainer and fuel inlet needle assembly. Remove the retainer and float shaft from the float lever. Remove the fuel bowl filler.
- Remove the fuel inlet needle, seat, filter screen and the main jets.
- Remove the booster venturi screw (accelerator pump discharge), booster and metering rod assembly and gasket. Remove the filter screen from the booster venturi screw. Invert the main body and catch the weight and ball. Remove the lift spring retaining clip and spring, separate the lift rod assembly from the booster. Do not disassemble the metering rod hanger from the lift rod.
- Remove the accelerator pump link and rod assembly. Remove the temperature compensated valve assembly.
- Remove the accelerator pump cover attaching screws. Remove the accelerator pump cover, diaphragm assembly and spring.
- If it is necessary to remove the Elastomer valve, grasp it firmly and pull it out. An Elastomer valve must be replaced whenever it has been removed.
See Figures 14 and 15
- Invert the main body and remove the enrichment valve cover and the gasket. Remove the enrichment valve with a box wrench or socket wrench. Remove the enrichment valve gasket and discard it.
- To remove the idle fuel mixture screws and springs, support the area under the limiter plug and using a pointed tool directed at the tang, lightly tap the plug forward.
See Figure 16
- If necessary, remove the nut and washer securing the fast idle adjusting lever assembly to the throttle shaft, and remove the lever assembly. If necessary, remove the idle screw and the spring from the fast idle adjusting lever.
- Remove the throttle positioner, if so equipped.
- If it is necessary to remove the throttle plates, lightly scribe the throttle plates along the throttle shaft and mark each plate in its corresponding bore with a number for proper installation. File off the staked portion of the throttle plate screws prior to their removal. Remove any burrs on the throttleshaft caused by the screw removal to prevent scoring of the throttle shaft bores as the throttle shaft is withdrawn. Catch the mechanical high speed cam located on the throttle shaft between the throttle plates.
- Remove the three screws that attach the aneroid assembly to the main body (if altitude compensated) and remove the assembly.
- Slide the throttle shaft assembly into the main body until it begins to enter the high speed bleed cam slot in the body. Holding the cam by the edge of the point, hold it in the slot and rotate the throttle shaft until it will pass through the cam. Rotate the shaft clockwise until the throttle lever clears the boss for the throttle solenoid positioners Off idle screw. Continue inserting the shaft into proper position, rotating as necessary to properly position the cam.
- Refer to the lines scribed on the throttle plates and install the throttle plates in their proper location with the screws snug, but not tight. Always use new screws when installing throttle plates.
- Close the throttle plates. Invert the main body, and hold it up to the light. Little to no light should show between the throttle plates and bores. Tap the plates lightly with a screwdriver handle to seat them. Hold the throttle plates closed and tighten the screws and stake them by crimping the exposed threads with diagonal cutters.
- If the aneroid was separated from the metering valve assembly, position a new gasket and the aneroid on the valve and install the attaching screws. Using a new gasket position the aneroid assembly to the main body and install the four attaching screws.
- Place the fast idle adjusting lever assembly on the throttle shaft and install the retaining washer and nut, tighten to 25 inch lbs. (3 Nm). If necessary install the fast idle screw and spring on the fast idle adjusting lever.
- Invert the main body. Install the enrichment valve and new gasket with a wrench and tighten to 110 inch lbs.
- Install the idle mixture adjusting screws and springs. Turn the screws in gently with your fingers until they just touch the seat, then back them out 1 1 / 2 turns. Install the enrichment valve cover and new gasket. The cover must be installed with the limiter stops engaged in the plugs.
- If the Elastomer valve was removed, lightly lubricate the tip of the new Elastomer valve and insert the tip into the accelerator pump cavity center hole. Using a pair of needle nosed pliers, reach into the fuel bowl and grasp the valve tip. Pull the valve in until it seats in the pump cavity wall and cut off the tip forward of the retaining shoulder. Remove the tip from the bowl.
The reduced cavity Elastomer valve can be used in place of the larger Elastomer valve but not vice-versa.
- Install the accelerator pump diaphragm return spring on the boss in the chamber. Insert the diaphragm assembly in the cover and place the cover and diaphragm assembly into position on the main body. Install and tighten the cover screws.
- Position the accelerator pump rod into the specified hole on the pump overtravel lever. Rotate the pump link and rod assembly toward the pump cover, support the area below and install the link using the roll pin. Position the TCP assembly and gasket, install and tighten three retaining screws.
See Figure 17
- Drop the accelerator pump discharge ball into the passage, stake the ball against the seat using a flat punch and gently tapping with a light hammer. Drop the weight into the passage in the main body.
- Position the new booster assembly gasket and the booster venturi assembly in the main body. Install the booster venturi screw including filter and gasket and tighten to 75 inch lbs. (8 Nm).
- Install the main jets, be sure the right jets are installed. Install the fuel inlet seat, filter screen, baffle and new gasket.
- Install the fuel inlet needle assembly in the fuel inlet seat.
- Slide the float shaft into the float lever. Position the float shaft retainer on the float shaft.
- Insert the float assembly into the fuel bowl and hook the float lever tab under the fuel inlet needle assembly. Place the float damper spring on the shaft. Insert the float shaft into its guides at the sides of the fuel bowl. Install the fuel bowl filler.
- With a screwdriver, position the float shaft retainer in the groove on the fuel inlet needle seat. Check and set the float level setting , ensure that the float does not interfere with the Elastomer valve.
- Position the fast idle cam lever on the thermostatic choke shaft and lever assembly. The bottom of the fast idle cam lever adjusting screw must rest against the tang on the choke lever. Insert the choke lever into the rear of the choke housing. Position the choke lever so that the hole in the lever is to the left side of the choke housing.
- Install the fast idle cam rod on the fast idle cam lever. Place the fast idle cam on the fast idle cam rod and install the retainer. Place the choke housing vacuum pick-up port to the main body gasket on the choke housing flange.
- Position the choke housing on the main body and at the same time, install the fast idle cam on the hub of the main body. Position the gasket, with sealant and install the choke housing attaching screws. Install the fast idle cam retainer.
- Position the gasket and install the choke cap using new breakaway screws.
Be sure the bimetal spring tab is engaged in the slotted choke shaft lever.
- Engage the choke pulldown rod in the diaphragm assembly link. Rotate the assembly to align the mounting bracket with the main body casting. Attach the pulldown rod and install the E-clip. Install and tighten the two attaching screws. Connect the vacuum supply tube to the correct vacuum base tube connection. Adjust choke assembly as necessary.
- Position the fuel bowl gasket and the choke rod plastic seal on the main body. Position the airhorn on the main body and gasket so that the choke plate rod fits through the seal and the opening in the main body.
- Insert the rod end of the choke plate rod into the automatic choke lever. Install the airhorn attaching screws and the carburetor identification tag. Install the choke plate rod retainer. Install the air cleaner anchor screw.
- The carburetor must be install on engine for final adjustments.
See Figure 18