SERVICE CHRYSLER CORPORATION

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Quadrajetcarburetor ................................................................. 1 Carburetor Identification .......................................................... 1 The Float System ................................................................. 1 Idle System ...................................................................... 2 Off Idle System ................................................................... 2

............................................. Main Metering System (Passenger Car) 3 Main Metering System (Truck) ..................................................... 3

.................................................... Power System (Passenger Car) 4 ............................................................. Power System (Truck) 4

Secondary System ................................................................ 5 ............................................................ Metering Rods Primary 5

Metering Rods Primary ............................................................ 6 Accelerator Pump System ......................................................... 6 Choke System ................................................................... 6 Choke System Components ....................................................... 7

..................................... Choke Vacuum Diaphragm Assembly Features 7 Preliminary Servicing ................................................................ 7

................................................................ Prior To Servicing 7 Preliminary Servicing ............................................................ 8

Idle Air Bleed Valve Removal .......................................................... 9 Idle Air Bleed Valve Installation ........................................................ 9

Air Horn Removal ................................................................. 10 Air Horn Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Float Bowl Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Choke Cover Removal ................................................................ 14 Choke Removal ....................................................................... 15 Choke Cover Installation .............................................................. 15

Throttle Body Disassembly ........................................................ 16 Concealment Plug Removal ........................................................... 16 Cleaning & Inspection ................................................................. 16 Float Bowl Assembly .................................................................. 16 Air Horn Installation ................................................................. 19 Float Adjustment ..................................................................... 21 Float Level External Check ............................................................ 21 Rich Mixture Adjustment .............................................................. 21 Air Valve Spring Adjustment ........................................................... 22 Choke Coil Lever Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Using Choke Valve Angle Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Choke Rod Fast Idle Cam Adjustment (Angle Gauge Method) ........................... 23 Choke Vacuum Kick Adjustment (Angle Gauge Method) ................................. 24 Air Valve Rod Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Unload Adjustment (Angle Gauge Method) ............................................. 24 Secondary Lockout Adjustment ....................................................... 25

QUADRAJET CARBURETOR The Rochester Quadrajet Carburetor is a four barrel, two stage design. The primary side of the carburetor has two smaller bores, each containing a triple venturi arrangement equipped with a plain tube nozzle. The triple venturi, plus the small bores provides excellent fuel atomization and delivery in the off-idle and part throttle ranges of engine operation. There are three main carburetor assem- blies; the air horn or top of the carburetor, the float bowl or main body, and throttle body. These components with their own individual pieces control six basic operating systems:

1. Float System 2. Idle System 3. Main Metering System 4. Power System 5. Accelerator Pump System 6. Choke System

Carburetor Identification (Fig. 1)

7 my, A MODEL NUMBER B ASSEMBLY PLANT CODE C YEAR

D JULIAN DATE

The carburetor identification number is stamped vertically into the float bowl near the secondary throttle lever. If for any reason the float bowl is replaced these numbers must be transferred to the new bowl, follow the manufacturer's instructions contained in the service package. It's necessary to refer to the model number when servicing the carburetor.

The Float System (Fig. 2)

FLO

FLOAT SEAT

VENT SLOT

r -FLOAT ASSE

:LOAT BOWL

MBLY

I The purpose of the float system is to maintain an adequate supply of fuel in the fuel bowl for use by the various fuel delivery systems. A single float chamber supplies fuel to all carburetor circuits. A closed cell rubber float, brass needle and seat with

(Fig. 3)

FLOAT NEEDLE PULL CLlP LOCATION HOOK CLlP OVER EDGE OF FLAT ON FLOAT ARM FACING FLOAT PONTOON

a viton tip on the needle and a pull clip, are used to control the fuel level in the float chamber. The pre-determined fuel level is one of the more critical adjustments, too high a fuel level could cause flooding and very poor idle due to nozzle drip, as well as poor fuel economy and incorrect emissions. Too low a fuel level could cause a hesitation and poor performance due to the delay in fuel flow, or not enough fuel to produce a smooth transition from one circuit to the next.

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The float chamber also has an internal and an external venting system. The internal vent system is open to filtered air in the air cleaner, allowing balanced air pressure to act on the fuel chamber. This way, balanced air/fuel mixture ratios can be maintained throughout the full range of carburetor operations.

The fuel chamber is also vented externally through a tube in the air horn. Fuel vapors that form in the fuel chamber flow through this tube and are connected to a vapor canister by a rubber, gas resistant, hose. The canister vapor vent valve is a spring loaded normally open valve which is closed by manifold vacuum during engine operation, and opened by spring pressure when the engine is off, thus allowing the fuel vapors to be collected in the canister until normally purged. The venting of the fuel bowl to the vapor canister meets evaporative emission requirements and also improves hot engine restarting.

Idle System (Fig. 4)

FIXED IDLE AIR BY-PASS ,

IDLE AIR / I C

IDLE CHANNEL

IDLE TUBE.

C 1 LOWER IDLE

MAIN

J t l PLUG / ,' / OL-IDLE ( VALVE

IDLE MIXTURE NEEDLE IDLE DISCHARGE HOLE

Each primary bore of the carburetor has a separate and indepeident idle system to provide the correct air/fuel mixture to the engine during idle and off-idle operation. The idle system is required because the very low amount of air flow through the venturi is not sufficient to obtain efficient metering from the main discharge nozzles.

blades and allow fuel to be added to the air stream to produce a combustible mixture. The fuel is supplied to the discharge ports because of their location in the low pressure area, and fuel in the fuel chamber is vented to atmospheric pressure. The fuel is forced from the fuel chamber down through the main metering jets and into the main fuel wells, where it is picked up by the idle tubes extending into the wells.

The fuel is metered at the lower tip of the idle tubes and is drawn upward through the tubes by the vacuum signal being applied to the system. The fuel is then mixed with air at the top of each tube through the solenoid controlled idle air bleed valve, located

(Fig. 5)

in the air horn. The air bleed valve is controlled by the movement of the oxygen feedback solenoid plunger (mixture control solenoid) and controls the amount of air bleed into the idle svstem.

The mixture then passes past the side idle bleed, and idle channel restriction, continues down to the lower idle bleed where it is mixed with additional air, then to the off-idle discharge ports and the mixture screws, then into the carburetor bores and blends with the main air stream.

The basic operation of the idle system is very similar to previously used carburetors. The primary throttle Off-Idle Operation valves are held in a position determined by the curb As the primary throttle valves are opened to idle set screw. While the engine is running, a small increase engine speed, they pass by the slotted amount of air is passing between the throttle valves off-idle discharge ports, gradually exposing the and primary bores. Idle discharge ports are located ports to manifold vacuum. Further opening of the in the side of the below the primary throttle throttle valves increases air velocity through the

venturi sufficiently enough to cause low pressure at the lower idle air bleeds. As a result, the discharge continues throughout operation of the part throttle to wide open ranges, thereby supple- menting main discharge nozzle delivery. The idle mixture needle discharge holes and off-idle dis- charge ports will continue to supply fuel require- ments until air velocity in the venturi area is high enough to obtain fuel flow from the main metering system.

Main Metering System (Fig. 6 Passenger Car)

There are three Rochester Quadrajet Carburetors used on Chrysler vehicles. the oxygen feedback version will be used on the passenger carline, and the light duty truck will use the non-oxygen feed- back as will the heavy duty truck with minor calibration differences. The basic differences be- tween the oxygen feedback and the non-oxygen feedback versions, are found in the main and power systems.

The main metering system begins to operate as air flow increases through the venturi. As the air flow increases, the reducing of pressure at the tip of the nozzle draws the fuel through the main circuits of the carburetor. It supplies fuel from each bore to maintain the required air/fuel mixture to the engine during part throttle to wide open throttle operation. The main metering system is on the primary side of the carburetor and consists of two main metering jets, an electronically operated solenoid plunger, two main metering rods and springs, main well air bleeds, main discharge nozzles, and the venturi systems.

In the passenger car version, the fuel metering is controlled by two special stepped metering rods, operating in the primary jets, and positioned by a spring loaded plunger located in the oxygen feed- back solenoid (mixture control solenoid). The plunger in the solenoid is controlled (or pulsed) by an electrical signal received from the ESA/EFC computer.

The ESA/EFC is responding as a result of input from the oxygen sensor in the exhaust manifold, as well as from several inputs from other sensors such as temperature, intake manifold vacuum, etc. It alternately energizes the solenoid moving the metering rods to the lean position, or down into the primary jet, and de-energizes the solenoid moving the metering rods to the full rich position, or out of the primary jet. The alternate up and down move- ment of the solenoid plunger and rods in the jets occurs ten times every second. The length of time the plunger is in the energized or de-energized position, controlled by the ESA/EFC computer, is what determines how rich or lean the air/fuel mixture is delivered.

Main Metering System (Fig. 7 Truck)

I M A l N WELL AIR BLEEDS 1

FACTORY-METERING ADJUSTMENT SCRE

M A I N P O W E R PISTON I D O W N )

POWER SPRING PISTON V A C U U M MA!N

The main metering system basic operation for trucks is very much the same as for passenger car, except that it does not have the oxygen feedback solenoid with the benefit of the finer fuel control. The main system in the light and heavy duty truck incorporate the use of a power piston controlled by spring loads and .manifold vacuum differences.

During cruising speeds and light engine loads, manifold vacuum is high. In this mode of operation the engine will run on leaner mixtures than required during heavy loads. The primary main metering rods are connected to a vacuum responsive piston which operates against calibrated spring force, and manifold vacuum.

(Fig. 8) Power System (Fig. 10 Passenger Car)

PRIMARY METERING

QiYD d

POWER PISTON

METERING RODS

POWER PISTON

PRIMARY METERING JETS @-

When the manifold vacuum is high, it pulls the vacuum piston down, moving the metering rods down into the primary jet, leaning the mixture. As engine load increases and manifold vacuum de- creases, spring loading forces the vacuum piston up, drawing the metering rods out of the primary jets, enriching the fuel mixture enough to give the desired power necessary to overcome the addi- tional load.

(Fig. 9)

AIR VALVES SECONDARY IOPENI

I POWER SYSTEM I

The power system in the oxygen feedback carbu- retor provides extra mixture enrichment to meet power requirements under heavy engine loads and high speed operation. This is accomplished by the ESA/EFC being preprogrammed to keep the oxy- gen feedback solenoid (mixture control solenoid) in the rich operating mode, because of the inputs from the various sensors.

The computer determines from its sensor inputs when the increased speeds are reached, and the load has decreased and returns to adjusting the fuel mixture as before.

Power System (Fig. 11 Truck)

POWER PISTON ASSEMBLY I

APT METERING ROD SCREW

The power system in the non-oxygen feedback carburetor used on trucks has the same basic purpose in that it provides extra mixture enrichment to meet power requirements under heavy engine

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loads and high speed operation. Except, that it is accomplished in the same fashion as conventional pre-feedback carburetors. It consists of a vacuum operated power piston and spring, connected by a passage to intake manifold vacuum and was described in the main metering system -truck section.

Secondary System (Fig. 12)

AIR VALVES SECONDARY

I METERING RODS

I

METERING' MA'IN -SECONDARY DlSCS DISCHARGE THROTTLE VALVES

NOZZLES

The secondary system of the quadrajet has a separate and independent metering system. Fuel metering is controlled by spring-loaded air valves, metering orifice plates, secondary metering rods, secondary fuel wells with bleed tubes, fuel dis- charge nozzles, and accelerating. wells and tubes.

After the choke has warmed sufficiently to release the secondary throttle valve lock out, and the engine reaches a point where the primary bores cannot meet engine air fuel demands, the second- ary throttle valves will open, manifold vacuum (low

(Fig. 13)

pressure) is supplied directly beneath the second- ary air valve, and as the air valve begins to open passing the accelerating well ports, the ports are exposed to the low pressure. They immediately feed fuel from the wells on each side of the fuel chamber which helps to prevent momentary lean- ness until the fuel begins to flow in the secondary system.

In addition to the secondary air valve assisting in starting the flow of fuel, it rotates a plastic eccentric cam attached to the center that lifts the secondary metering rod hangar. As the hangar is lifted, it pulls the metering rods out of the secondary jets. Fuel then flows from the fuel chamber, through the secondary metering channels to the main well air bleed tubes then into the secondary discharge ports. The depth of the metering rods in relation to the air valve position are factory adjusted to meet air/fuel requirements - no change in this adjust- ment should be made.

Metering Rods Primary (Fig. 14)

Special two-step main metering rods (with return springs) are used on the primary side of the Quadrajet Carburetors. These rods have a two-digit number stamped on the upper end of the rod. The number is used for internal factory identification only, and does not indicate rod size or part number. If the need should arise to replace these rods they must be replaced in sets.

Metering Rods Primary (Fig. 14)

PART NO. IDENTIFICATION ASSEMBLY

(FOR FACTORY

Accelerator Pump System (Fig. 15)

DISCHARGE

DISCHARGE

DISCHARGE CHECK BALL

UMP PLUNGER

During rapid accelerations air flow increases almost instantaneously. The fuel flow, which is slower due to the weight, has a tendency to lag behind creating a momentary leanness. Also, there is a very short period of time when there is a very slight leanness when the idle system cannot supply enough fuel mixture before the main system supplies a sufficient amount to sustain engine operation. To prevent this the accelerator pump system is used.

The system consists of a spring loaded pump plunger and pump return spring, fuel passage, discharge check ball, retainer, and pump jets.

An expander spring is used in the pump cup for constant pump cup to pump wall contact. The pump

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cup is of the "floating" design. That is, as the pump is being drawn up, the cup unseats to allow fuel to be drawn past; and when the pump is being forced down, it seats and seals as it provides a solid charge of fuel on the downstroke.

The pump cup is operated by the pump lever on the air horn connected to the throttle lever by a rod. During throttle closing the pump shaft is forced up from the bottom of the well by the return spring. As it's moving up in the well, fuel flows through a vertical slot in the side of the pump well.

When the throttle valves are opened, the pump rod and lever forces the pump plunger downward sealing the cup against the rod and forces the fuel through the passages to the pump jets and into the venturi.

The spring on the pump shaft above the pump cup is the duration spring and is balanced with the pump return spring so a smooth sustained flow of fuel will be supplied. These springs are matched to the rate of movement of the linkage and plunger for proper duration and volume.

The system also requires a discharge check ball that seats in the pump discharge passage so air will not be drawn into the passage during the upward movement of the pump and prevent proper fill.

During higher air flow, a vacuum is created at the pump jets. To prevent the possibility of fuel being drawn from the pump well through the jets, a passage located just behind the jets leads to the top of the air horn to vent the circuit.

Choke System (Fig. 16)

AIR \ VALVE.

AIR VALVE ROD

CHOKE

VACUUMBREAK WITH LEAF - TYPE BUCKING SPRING

L ~ ~ ~ ~ ~ ~ ~ ~ ~ E R / / w \ 'GumEER FAST IDLE FAST IDLE

CAM FOLLOWER A D S J ~ ~ ~ ~ G

The off-set choke valve is mounted in the air horn above the primary carburetor venturi. The closed choke valve provides the correct air/fuel mixture

enrichment for cold engine starting. The choke valve also assists engine running during the warm- up period.

An electric choke coil is mounted in the integral choke housing. The system uses electrical current supplied to the choke coil which combined with the off-set choke valve and throttle position, control choke operation.

The Choke System Components are as in Fig. 17.

CHOKE LEVER - SCREW - CHOKE

LEVER ATTACHING

R O D C H O K E )y/ LEVER CHOKE INTERMEDIATE SHAFT bl

ROD - AUXILIARY

TO FLOAT BOWL (HOT AIR CHOKE ONLY)

SEAL - INTERMEDIATE CHOKE SHAFT (HOT AIR CHOKE ONLY)

\ SCREW - CHOKE SCREW. CHOKE

HOUSING ATTACH COIL LEVER

Choke Vacuum Diaphragm Assembly Features:

The vacuum assemblies used are either positive acting or time delayed vacuum diaphragm mecha- nisms, used to control choke value opening during engine start and warm-up. The positive acting units respond immediately to applied vacuum. They provide the correct choke value opening during engine cranking and initial start-up to prevent stalling or engine loading. Time delayed vacuum break units respond more slowly to applied vacuum and usually open the choke valve further after a few seconds of engine operation. Timing of vacuum diaphragm units is accomplished by an integral delay valve or by restricting vacuum to the dia- phragm chamber or the unit itself. The internal delay is an internal bleed check valve mounted inside the diaphragm chamber. Engine

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vacuum acting on the internal check valve bleeds air through a small hole in the valve which allows the vacuum diaphragm to move slowly inward. The vacuum restriction type uses a small restrictor orifice in the integral vacuum tube. The restriction acts to delay engine vacuum from building up too quickly inside the diaphragm chamber. This acts to delay the inward movement of the diaphragm plunger. in addition to the delayed vacuum unit which retards choke valve opening, an internal plunger bucking spring is used on the vacuum break plunger. The purpose of the plunger bucking spring is to offset tension of the thermostatic coil, with the addition of the bucking spring in the diaphragm plunger. The choke valve can be modulated through the thermostatic coil so that leaner mix- tures are maintained during warmer temperatures and richer mixtures for colder temperature operation. During extreme cold operation, the thermostatic coil has more tension than during warmer tempera- tures; consequently, the thermostatic coil operating against the bucking spring on the the vacuum diaphragm plunger compresses the plunger spring further, and the choke valve does not open as far, allowing richer mixtures for the colder temperatures. The opposite is the true when, during temperatures, the thermostatic coil has less tension during the starting period so that the plunger bucking spring is not compresses as much and the vacuum diaphragm plunger opens the choke valve further supplying a leaner mixture for the warm-up period. This way, choke valve opening can be varies to give the correct fuel mixtures, depending on the outside temperatures.

Prior To Servicing

All too often performance complaints are directed at the carburetor unjustly. Many of these complaints can be cured by a simple routine check of vacuum hose connections and their routing or, loose, misadjusted or malfunctioning engine or, electrical components. A thorough road test and check of minor carburetor adjustments should precede rna- jor carburetor service. The best approach to analyz- ing carburetor complaints should include a routine check of such areas as:

PRELIMINARY SERVICING 1. Inspection of all vacuum hoses and actuators

for leaks. Refer to the vacuum hose routing label located under the hood in the engine compartment for proper hose routing.

2. Check torque of intake manifold bolts and carburetor mounting bolts for proper specification.

3. Perform cylinder compression test.

4. Check, clean, or replace spark plugs, as necessary.

5. Check resistance or spark plug cables.

6. lnspect ignition primary wire and vacuum advance operation. Test coil output voltage, primary and secondary resistance. Replace all parts that do not meet specification.

7. Check ignition timing.

8. Check carburetor idle mixture specification at tailpipe, and speed adjustment. Adjust throttle stop screw to specifications.

9. Test fuel pump pressure.

10. Check emission controls for proper operation, such as the EGR valve, and for proper gasket condition.

11. Check air filter element for cleanliness, and replace as necessary.

12. lnspect crankcase ventilation system.

In normal circumstances, and with normal service, the mixture should not require adjustment. The idle set rpm can be checked without removal of the tamper resistant plugs. Tampering with carburetor mixture screws is in violation of Federal law, adjustment of the carburetor idle, air/fuel mixture can only be done under certain circumstances. Adjustment should only be considered if an idle defect still exists after normal diagnosis has re- vealed no other faulty condition, such as, incorrect idle speed, faulty hose or wire connection, etc. The only other condition that would require idle air/fuel mixture adjustment would be after a major overhaul.

IDLE AIR BLEED VALVE REMOVAL

sion fluid. Install thick seal in upper groove and thin seal in lower groove (Fig. 19).

WARNING: Safety glasses must be worn during this operation to protect eyes from (Fig. 19)

metal shaving damage.

The idle air bleed valve is set at the fac:tory and capped with a tamper resistant cover. The valve assembly should only be removed if servicing is required or when the air horn assembly must be soaked in carburetor cleaner. The valve should be adjusted only after servicing or if the lean mixture screw or rich mixture screw has been adjusted. If the idle air bleed valve is to be removed, the following steps must be performed.

(1) Cover internal bowl vents and air inlets to the bleed valve with masking tape (Fig. 18).

(Fig. 18)

MASKING TAPE

RIVET I IDLE AIR BLEED

ICK 0 - RING

(2) Install idle air bleed valve in air horn making sure that there is proper thread engagement.

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(Fig. 20)

(2) Carefully align a number 35 (.11OU) drill bit on rivet head. Drill only enough to remove rivet head.

(3) Use a suitably sized punch to drive out the remainder of the rivet from the casting. Re- peat this procedure with the other rivet. Lift out cover and remove any pieces of rivet still inside tower. Use shop air to blow out any remaining chips.

(4) Remove idle air bleed valve and discard "0" ring seals from valve. New "0" ring seals are required for reassembly. The idle air bleed valve is serviced as a complete assembly only.

IDLE AIR BLEED VALVE INSTALLATION (1) Lightly coat two new "0" rings with transmis-

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AIR BLEED VALVE

SOLENOID PLUN

(3) Insert idle air bleed gauging Tool C-4899 (Fig. 22) (BT-8353B) in left side "D" shaped hole in air horn casting (Fig. 20). The upper end of the tool should be Dositioned over the oDen cavity next to the idle air bleed valve.

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(4) Hold gauging tool down lightly so that sole- noid plunger is against solenoid stop. Adjust bleed valve so that tool will pivot over and just contact top of valve.

(5) Remove gauging tool.

Air Horn Removal

(1) Remove upper choke lever retaining screw and remove choke lever (Fig. 21).

(Fig. 21)

(2) Remove choke rod from lower lever inside float bowl casting. Remove rod by holding lower lever outward with a small screwdriver and twisting rod counterclockwise.

(4) Remove pump link retainer and remove link from lever (Fig. 23).

(Fig. 23)

(3) Remove small screw (# 10 torx head) from I I metering rod hanger and remove hanger and metering rods (Fig. 22).

(5) Remove choke vacuum diaphragm hose from tube on float bowl.

(6) Remove air horn mounting screws and sec- ondary air baffle deflector (Fig. 24).

(Fig. 24) (Fig. 25)

SCREW PLUG

RICH MIXTURE STOP SCREW PLUG LOCATION

(3) Use a suitable punch to drive out lean mixture screw plug and rich mixture screw plug (Fig. 26).

(7) Remove air horn from float bowl by lifting it straight up. The air horn gasket should re- (Fig. 26) main on the float bowl. Use care not to damage the oxygen feedback connector or the small tubes attached to the air horn. These tubes are permanently attached to the air horn.

AIR HORN DISASSEMBLY (1) Remove choke diaphragm screws and sepa-

rate diaphragm from air horn. Remove choke diaphragm link.

(2) Invert air horn and remove rich mixture stop screw using Tool C-4898 (BT-7967A) (Fig. 25).

(4) Remove idle air bleed valve, if air horn is to be soaked in carburetor cleaner or if the valve is to be serviced.

(5) Remove staking from accelerator pump seal retainer and remove seal and seal retainer from air horn if air horn is to be soaked in carburetor cleaner (Fig. 27).

(Fig. 27) (Fig. 29)

/

FLOAT BOWL DISASSEMBLY (5) Carefully lift out each metering rod and spring assembly from guided metering jets. Use

(1) Remove solenoi,d metering rod plunger by care in handling metering rods to avoid lifting it straight up (Fig. 28). damage (Fig. 30).

(Fig. 28) (Fig. 30)

(2) Remove and discard air horn gasket. (6) Remove attaching screw from oxygen feed-

(3) Remove accelerator pump plunger from pump well.

back solenoid (Fig. 31). Do not remove solenoid at this time.

(4) Remove plastic filler block from fuel bowl (Fig. 29).

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(Fig. 31) (Fig. 32)

ADJUSTING TOOL IXTURE SCREW

(9) Remove float assembly and float needle by pulling up on retaining pin (Fig. 33).

(7) Use Tool (2-4898 (BT-7928) to remove lean mixtwe solenoid screw. Remove feedback solenoid assembly. No attempt should be made to remove plunger spring or connector and wires from solenoid as the solenoid is serviced as a complete assembly.

(8) Remove solenoid screw tension spring lo- cated next to float hanger pin and solenoid tension spring from bottom of float bowl (Fig. 32).

(Fig. 33)

(10) Remove needle seat and gasket from float bowl.

(1 1) If it is necessary to remove primary main metering jets, use Tool C-4898 (BT-7967A) (Fig. 34).

(Fig.. 34)

JET REMOVAL

PRIMARY MAIN METERING JETS

(1 2) Remove pump discharge check ball retainer. Invert bowl and catch check ball. (Fig. 35).

(Fig. 35)

(1 3) Remove secondary air baffle, if replacement is required.

(14) If float bowl is to be soaked in carburetor cleaner, remove solenoid idle stop, choke assembly, and choke intermediate shaft cup seal.

(1 5) Remove fuel inlet nut, gasket, filter assembly and spring. Discard filter assembly and gas- ket (Fig. 36).

(Fig. 36) ' FUEL'INLET 1 FILTER

NUT GASKET I

SPRING

(1 6) Remove three throttle body to bowl attaching screws and lockwashers and remove throttle body assembly (Fig. 37).

(Fig. 37)

THROTTLE BODY TO BOWL SCREWS

(1 7) Remove and discard throttle body to bowl gasket.

CHOKECOVERREMOVAL (1) Support carburetor in holding fixture C-3886

to avoid throttle plate damage.

(2) Drill out three choke cover retaining rivets using a number 21 (.159") drill. Only drill enough to remove rivet heads (Fig. 38).

(Fig. 38) CHOKE COVER INSTALLATION

RIVETS AND CHOKE COVER

RETAINERS

(3) Remove choke cover by pulling it straight out.

(4) Drive out remainder of rivets from choke housing using a suitable punch and small hammer.

CHOKE REMOVAL (1) Remove choke cover.

(2) Remove choke mounting screw from inside choke housing and slide choke assembly out of float bowl (Fig. 39).

(Fig. 39)

(3) Remove secondary throttle valve lock out lever from float bowl.

(1) Place cam follower on highest step of fast idle cam.

(2) Install thermostatic cover and coil assembly in the choke housing making sure coil tang engages the inside coil pick-up lever (Fig. 40).

(Fig. 40)

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(3) Reinstall choke cover retainers and blind rivets using a suitable blind rivet tool (Fig. 41).

(Fig. 41)

CHOKE LEVER --L

SCREW -CHOKE LEVER ATTACHING

R O D CHOKE

.EVER - INTERMEDIATE CHOKE SHAFT J

S C R E L - CHOKE S C R E W . CHOKE I HOUSING ATTACH ' COIL LEVER I

Throttle Body Disassembiy (1) Support carburetor in holding fixture C-3886

to avoid throttle plate damage.

(2) Remove pump rod from throttle lever by rotating rod until tang on rod aligns with lever.

(3) Remove concealment plugs.

CONCEALMENT PLUG REMOVAL (FIG. 42)

(Fig. 42)

- 1 CENTER PUNCH \

. CONCEALMENT PLUGS

(1) Invert carburetor and use hacksaw to make two parallel cuts in the throttle body. Make cuts on each side of the locator points beneath the concealment plug. The cuts should reach down to the plug but should not extend more than '/8 inch beyond the locator points. The distance between the saw cuts will depend on the size of the punch to be used.

(2) Place a flat punch at a point near the ends of the saw marks in the throttle body. Hold the punch at a 45" angle and drive it into the throttle body until the casting breaks' away, exposing the steel plug.

(3) Repeat the procedure for the other conceal- ment plug.

(4) Use Tool C-4895 to remove idle mixture screws.

CLEANING AND INSPECTION Except for the air horn assembly with idle air bleed valve installed, the carburetor should be cleaned in a cold immersion-type cleaner such as Carbon

X (X-55) or its equivalent. The air horn assembly, with idle air bleed valve in place, should be cleaned using only a low volatility cleaning solvent.

The air horn with bleed valve, solenoid idle stop, thermostatic choke cover and coil, rubber parts, plastic parts, diaphragms, pump plunger, etc., should not be soaked in carburetor cleaner. This soaking can cause these parts to swell, harden, or distort. Also, provide special protection for the metering rods and jets and idle air bleed valve (if removed) when cleaning, to prevent damage to these critical parts.

(1) Thoroughly clean all metal parts and blow dry with compressed air. Make sure all fuel pas- sages and metering are free of burrs and dirt. Do not pass drill or wire through jets.

(2) lnspect upper and lower surfaces of carbu- retor castings for damage.

(3) lnspect holes in levers for excessive wear or out-of-round conditions. If worn, levers should be replaced.

(4) lnspect plastic parts for cracks, damage, etc. Replace, if necessary.

FLOAT BOWL ASSEMBLY (1) Install new float bowl to throttle body gasket

over locating dowels on bottom of float bowl.

(2) Install throttle body over dowels on float bowl. Install three throttle body mounting screws and tighten securely (Fig. 43).

(Fig. 43)

1 THROTTLE BODY 1

(3) Support carburetor with holding fixture C- static choke coil lever is properly aligned 3886 to avoid throttle plate damage. when both inside and outside levers face

(4) lnstall fuel inlet filter spring, a new filter toward fuel inlet. lnstall inside lever retaining

assembly, new gasket, and inlet nut. Tighten screw into end of intermediate choke shaft

nut to 24 N-m (18 foot-pounds) (Fig. 44). and tighten securely (Fig. 45).

(9) lnstall lower inner choke rod lever into cavity (Fig. 44) in float bowl.

FUEL INLET FILTER NUT GASKET SPRING

(5) lnstall new cup seal into insert on side of float bowl for intermediate choke shaft. Lip on cup seal faces outward (Fig. 45).

(Fig. 45)

(6) lnstall secondary throttle valve lock-out lever on float bowl boss with recess in lever hole facing inward (Fig. 45).

(7) lnstall fast idle cam on intermediate choke shaft with steps on cam facing downward (Fig. 45).

(10) lnstall choke housing to bowl, sliding inter- mediate choke shaft into lever. A pair of needle-nose pliers may be used to hold lower lever in correct position while installing the choke housing. The intermediate choke shaft lever and fast idle cam are in correct position when the tang on lever is beneath the fast idle cam (Fig. 46).

(Fig. 46)

(11) lnstall choke housing retaining screw and washer, tighten securely (Fig. 47).

(8) Carefully install fast idle cam and intermedi- ate choke shaft assembly in choke housing. lnstall thermostatic coil lever on flats on intermediate choke shaft. Inside thermo-

(Fig. 47)

(1 2) If removed, install air baffle in secondary side of float bowl with notches toward the top. Top edge of baffle must be flush with bowl casting.

(1 3) If removed, install baffle inside of pump well with slot toward bottom.

(14) lnstall pump discharge ball and retainer screw. Tighten retainer screw securely (Fig. 48).

(Fig. 48)

(15) If removed, carefully install primary main metering jets using Tool C-4898 (BT-7928).

(1 6) lnstall large mixture control solenoid tension spring over boss on bottom of float bowl (Fig. 49).

(Fig. 49)

(17) lnstall needle seat assembly with gasket.

(18) To make adjustment easier, carefully bend float arm upward slightly at notch in arm before assembly.

(19) lnstall float needle onto float arm by sliding float lever under needle pull clip. Proper installation of the needle pull clip is to hook the clip over the edge of the float on the float arm facing the float pontoon.

(20) lnstall float hinge pin into float arm with end of loop of pin facing pump well. lnstall float assembly by aligning needle in the seat and float hinge pin into locating channels in float bowl. Do not install float needle pull clip into holes in float arm (Fig. 50).

(Fig. 50) (Fig. 51)

(21) Perform float adjustment.

(22) lnstall feedback solenoid tension spring.

(23) lnstall feedback solenoid. Check that pin on bottom of solenoid is aligned with hole in bottom of bowl.

(24) Insert lean mixture screw through hole in solenoid bracket and install screw so that at least the first six threads of screw are engaged in bowl.

(25) lnstall gauging Tool C-4899 (BT-8253A) over the left metering jet rod guide and install solenoid plunger.

(26) Hold plunger against solenoid and turn sole- noid screw using Tool C-4898 (BT-7928) until solenoid plunger contacts gauging tool (Fig. 51).

(27) Remove solenoid plunger and gauging tool.

(28) lnstall feedback solenoid attaching screw. (29) lnstall plastic filler block.

(30) lnstall metering rod and spring assemblies. Do not force metering rod into jet. Use extreme care in handling these parts to avoid damage to rods and springs. If metering rods, jets and springs are replaced, they must be installed in matched sets.

(31) lnstall pump return spring in pump well. lnstall pump plunger assembly in pump well.

(32) Hold down pump plunger and install air horn gasket. Position gasket over locating pins on float bowl.

(33) Hold down on air horn gasket and pump plunger and install feedback solenoid plunger. Check that plunger arms engage top of each metering rod. If feedback solenoid is replaced, the solenoid and plunger must be installed as a matched set.

AIR HORN INSTALLATION (1) Carefully lower air horn assembly onto float

bowl. Check that bleed tubes and acceler- ating well tubes are positioned properly. Do not force the air horn assembly onto the bowl, but lower it lightly into place.

(2) lnstall secondary air baffle and air horn mounting screws. Tighten all screws evenly and securely (Fig. 52).

CHOKE VACUUM KICK ADJUSTMENT (ANGLE GAUGE METHOD) (Fig. 62)

(Fig. 62)

BUCKING SPRING, IF USED, MUST BE SEATED AGAINST LEVER

AIR VALVE ROD ADJUSTMENT (Fig. 63)

(Fig. 63)

3 025 PLUG GAGE BETWEEN O ROD AND END OF SLOT @ USE VACUUM SOURCE AT LEAST 18 H G T O SEAT VACUUM BREAK PLUNGER PLUG AIR BLEED HOLES WHERE APPLICABLE

TO ADJUST GAGE CLEARANCE T O 025 WITH VACUUM

AT LEAST 18 H G

(1) Use tool C-4207-A to apply at least 18 inches H.G. to vacuum nipple on choke vacuum diaphragm.

(2) Close air valve.

(3) Insert a .025 inch plug gauge between rod and end of slot.

(4) Bend rod to adjust clearance to .02i5 inch.

UNLOAD ADJUSTMENT (ANGLE

(1) Attach rubber band to green tang of interme- GAUGE METHOD) (Fig. 64)

diate choke shaft as shown. (Fig. 64) (2) Open throttle to allow choke valve to close. I

(3) Set up angle gauge and set to specifications.

(4) Use tool C-4207A to apply at least 18 inches H.G. to nipple on choke diaphragm. The air valve rod must not restrict plunger from retracting fully. If necessary, bend rod to permit full plunger travel. Final rod clearance must be set after vacuum kick setting has been made.

(5) With at least 18 inches H.G. still applied, adjust screw to center bubble.

CHOKE COIL LEVER ADJUSTMENT (Fig. 59)

(1) Close choke valve.

(2) Rotate degree scale until zero is opposite pointer.

(Fig. 59) (3) Center leveling bubble.

I I

I 1 (4) Rotate scale to specified angle.

COIL ASSEMBLY. OF FAST IDLE CAM

(1) Remove choke cover.

(2) Place fast idle cam follower on highest step of fast idle cam.

(3) Push up on choke coil lever to close choke valve.

(4) Insert a .I20 inch plug gauge as shown.

(5) Lower edge of lever should just contact gauge.

(6) Bend choke rod to adjust.

USBNG CHOKE VALVE ANGLE GAUGE (Fig. 60)

(Fig. 60)

(5) Adjust linkage to center the bubble.

CHOKE ROD FAST IDLE CAM ADJUSTMENT (ANGLE GAUGE METHOD) (Fig. 6 1)

(Fig. 61)

(1) Attach rubber band to green tang of interme- diate choke shaft as shown.

(2) Open throttle to allow choke valve to close.

(3) Set up angle gauge and set angle to specifications.

(4) Place cam follower on second highest step of cam against rise of high step. If cam follower does not Oontact cam, turn in fast idle screw until it does.

(5) Adjust by bending tang of fast idle cam until bubble is centered.

(Fig. 57) (Fig. 58)

RICH MIXTURE

(2) Read at eye level the mark on the gauge in inches, that lines up with the top of the air horn casting. Record reading.

(3) Lightly press on the gauge and again read and record the mark on the gauge that lines up with the top of the air horn casting.

(4) Substract the dimension recorded in step 2 from the dimension recorded in step 3. The difference in dimensions is total solenoid plunger travel.

(5) Insert Tool C-4898 (BT-7929) into access hole in air horn and adjust rich mixture screw to obtain 4/32 inches total solenoid plunger travel (Fig. 58).

(6) Remove tool and proceed with plug installation.

AIR VALVE SPRING ADJUSTMENT

(1) Loosen lock screw using 3/32 rncbi wrench.

(2) Turn tension-adjusting screw coeinler-clock- wise until air valve opens par; way

(3) Turn tension-adjusting screw clsckw~se until air valve just closes. Then, turrl adjusting scew clockwise the number of turns specified.

(4) Tighten lock screw.

(5) Apply lithium base grease to iubr~cate con- tact area.

(8) lnstall plug into access hole for lean mixture screw and using a suitably sized punch, drive plug into air horn so top of plug is even with air horn.

(9) lnstall plug into access hole for rich mixture screw and drive plug air horn so that plug is 1 /16 inch below air horn surface. The lean mixture plug must be installed to retain the screw setting and to prevent vapor loss. The rich mixture plug must be installed to retain the screw setting.

(10) lnstall idle air bleed valve.

(1 1) lnstall choke cover.

(1 2) lnstall chocke vacuum diaphragm hose.

(13) lnstall solenoid idle stop.

FLOAT ADJUSTMENT (1) Remove throttle body, feedback solenoid

plunger, and throttle body gasket.

(2) Remove plastic float bowl. inster.

(3) Hold float bowl retainer firmly in place.

(4) Push float down lightly against needle.

(5) Measure float height from top of casting to top of float at a point 3/16 inch from end of float.

(6) Float level should be within 1 /16 inch of specifications.

(7) If float leve is too high, hold retainer in place and push down on center of float pontoon to obtain correct setting.

(8) If float level is to low, perform the following steps:

(a) Remove metering rods and feedback solenoid connector screw.

(b) Count and record for reassembly the number of turns needed to lightly bottom lean mixture screw.

(c) Remove metering rods and feedback sole- noid assembly.

(d) Bend float upward to adjust. Recheck float level.

FLOAT LEVEL EXTERNAL CHECK (Fig. 56)

(Fig. 56)

(1) With carburetor installed on engine, and engine idling, choke wide open, insert gauge C-4900 (BT-8420A) in vent hole and allow gauge to float freely. Do not press down on gauge as flooding or float damage may result.

(2) Observe lines on gauge that line up with the top of the casting. Setting should be within 1.58mm (f 2/32 in.) of specified float level setting. Incorrect fuel pressure will cause false readings.

(3) If float level is not to specifications, remove.

RICH MIXTURE ADJUSTMENT (1) lnstall external float gauging Tool C-4900

(BT-7720) in the vertical "D" shaped vent hole in air horn (Fig. 57) and allow it to float freely.

(e) Reassemble float bowl components. Lightly bottom lean mixture then back out screw to number of turns previously recorded. Reinstall.

(Fig. 52) (5) Install metering rod hanger and metering rods and tighten screw securely. Work air valves up and down several times to check operation (Fig. 54).

(Fig. 54)

(3) Install air vavle rod into slot in lever. Install other end of rod in choke vacuum diaphragn and install vacuum diaphragm.

(6) Connect choke rod into lower choke lever (4) Connect pump link to pump lever and install inside bowl cavity. Install choke rod in upper

retainer (Fig. 53). lever and install choke lever (Fig. 55).

(Fig. 53) (Fig. 55)

(7) Adjust the rich mixture stop screw.

20

(1) Attach rubber band to green tang of interme- diate choke shaft.

(2) Open throttle to allow choke valve to close.

(3) Se'l up angle gauge and set angle to specifications.

(4) Mold secondary lockout lever away from pin.

(5) Holcl throttle lever in wide open position.

(6) Adjust by bending tang of fast idle lever until bubble is centered.

SECONDARY LOCKOUT ADJUSTMENT

(1) To check secondary lockout lever adjust- ment:

(a) close choke valve

(b) close throttle valve

(c) insert a .015 inch plug gauge as shown

Id) Send pin to achieve .015 inch clearance

(2) To check secondary lockout opening clearance:

(a) hold choke valve wide open by pushing down on tail of fast idle cam

(b) insert a .015 inch plug gauge as shown

NOTES

(c) file end of pin if necessary to achieve .015 inch clearance. Check that no burrs are left after filing.