Carburetor - Rochester e4mc 4-bbl Cadillac Brougham I

APPLICATION

GENERAL MOTORS CARBURETOR NUMBER

IDENTIFICATION

The Rochester E4MC carburetor number is stamped vertically on float bowl, near secondary throttle. This number must be used for ordering replacement components and performing adjustments. Carburetor identification number must be transferred onto new float bowl if float bowl is replaced.

This carburetors are equipped with a computer control feedback system. this is indicated by the first letter "E" of the identification number. The last letter of the identification number indicates type of choke used. Letter "C" indicates a hot air type choke.

DESCRIPTION

The 2-stage, downdraft design, E4MC carburetor is composed of 3 main components, air horn, float bowl and throttle body. E4MC models have 2 vacuum break diaphragm assemblies, primary and secondary.

The E4MC carburetor is used in conjunction with the Computer Command Control (CCC) computerized engine control system. Carburetor is equipped with an electrically-actuated Mixture Control (MC) solenoid mounted in the float bowl. Fuel delivery is controlled by the MC solenoid in response to signals generated by the computer. Fuel metering is controlled by stepped metering rods and jets.

A Throttle Position Sensor (TPS) is contained in the carburetor and varies resistance reading to the computer, indicating throttle position changes. An Idle Load Compensator (ILC) is used on E4MC models. The ILC increases idle speed during increased engine load conditions such as A/C operation or increased power steering loads. ILC will also increase throttle opening during periods of extended deceleration (such as coasting downhill).

FLOAT LEVEL (ON-VEHICLE)

1. Operate engine until choke is fully open. Install Float Gauge (J-34935-1) in vent slot. (Scheme 1) Allow gauge to float freely. DO NOT press downward on float gauge or float damage may occur.
2. Observe indicator mark in relation to top of casting. This reading should be within 2/32" of float level specification. See CARBURETOR ADJUSTMENT SPECIFICATIONS table. Excessive fuel pump pressure will cause a high float level.
3. Remove air horn and adjust float level if not within specification. See FLOAT LEVEL under ADJUSTMENTS in this article.

Scheme 1

HOT AIR CHOKE

Note. Electric choke must be tested only when choke thermostat temperature is approximately 70°F (21°C).

1. Allow engine to reach normal operating temperature. Ensure choke valve opens fully. If valve fails to open fully, check choke housing and hot air inlet for sufficient heat to choke coil.
2. If insufficient heat is indicated, check for vacuum loss to choke housing, restricted choke housing heat inlet, restricted hot air inlet pipe and restricted manifold choke heat stove passages. Repair as required.

VACUUM BREAK

1. Inspect vacuum break for bleed hole in vacuum tube. Plug bleed hole with tape prior to testing vacuum break. Using vacuum pump, apply 15 in. Hg vacuum to vacuum break and note vacuum reading.
2. Vacuum reading should hold for at least 20 seconds. Apply finger pressure to plunger to determine if plunger has obtained full travel. Replace vacuum break if plunger did not obtain full travel or failed to hold vacuum.

IDLE LOAD COMPENSATOR (ILC)

1. Ensure cap located on end of ILC is good condition. Vacuum leakage will occur if damaged. Open throttle, allowing ILC plunger to extend. Apply finger pressure to plunger. NOTE: Plunger is not connected directly to the diaphragm and will not retract without applying light finger pressure when vacuum is applied.
2. Using vacuum pump, apply 20 in. Hg vacuum to ILC. Note vacuum reading and plunger operation. Plunger should retract and vacuum should hold for at least 20 seconds. Release vacuum and plunger should extend. Replace ILC if plunger did not extend or failed to hold vacuum.

FLOAT LEVEL

1. Remove air horn, solenoid plunger, air horn gasket and metering rods. Remove plastic float bowl insert. If solenoid lean mixture screw requires removal, use Mixture Control Tool (J-28696 or BT-7928). Count and record number of turns required to lightly seat lean mixture screw prior to removal.
2. Install Bracket (J-34817-1 or BT-8227A-1) on float bowl. (Scheme 2) Install Float Positioner (J-34817-3 or BT-8227-A) on float bowl with pin contacting outer edge of float lever.
3. Using "T" Scale (J-9789-90 or BT-8037), measure distance from top of casting to top of float, approximately 3/16" from large end of float. Float level must be within 2/32" of float level specification. See CARBURETOR ADJUSTMENT SPECIFICATIONS table.
4. If float level requires adjustment, use Float Adjuster (J-34817-15 or BT-8233) to bend float lever for correct setting. Recheck float level after each adjustment. Ensure float alignment is straight and does not contact float bowl.
5. Lightly seat lean mixture screw and readjust to original location (if removed). Reverse removal procedure for remaining components. Tighten air horn in correct sequence. (Scheme 17)

Scheme 2

MIXTURE CONTROL SOLENOID MIXTURE SCREW

1. Install Mixture Control Solenoid Gauge (J-33815-1 or BT-8253-A) over throttle lever side metering jet guide. Temporarily install solenoid plunger.
2. Install lean mixture screw 6 threads. Install rich limit stop. Hold solenoid plunger downward against solenoid stop. Using Mixture Adjuster (J-28696-10 or BT-7928), slowly turn lean mixture screw in or out until solenoid plunger just contacts solenoid stop and mixture control solenoid gauge. (Scheme 3)
3. Adjustment is correct when solenoid plunger is contacting BOTH the solenoid stop and gauge. Remove solenoid plunger and gauge. Install plug at proper location. (Scheme 5)

Scheme 3

MIXTURE CONTROL SOLENOID STOP SCREW

1. With solenoid lean mixture screw properly adjusted and air horn installed, install Float Gauge (J-34935-1 or BT-8420-A) in air horn vent hole. Allow float gauge to contact mixture control solenoid plunger. (Scheme 4) Note line indicated with top of air horn casting.
2. Press downward on float gauge and note indicator mark. Release float gauge. This difference between the indicator lines is the solenoid plunger travel.
3. Using Stop Screw Adjuster (J-28696-10 or BT-7928), turn rich mixture stop screw until total solenoid travel equals 4/32" (3.17 mm).
4. After adjustment, install lean mixture screw plug and rich mixture stop screw plug. Plugs must be installed at specified location to seal settings and to prevent fuel vapor loss. (Scheme 5)

Scheme 4

Scheme 5

AIR BLEED VALVE

1. Install Air Bleed Valve Gauge (J-33815-2 or BT-8253-B) in throttle side of vent hole of air horn so gauge contacts solenoid plunger. (Scheme 6)
2. Position upper end of air bleed valve gauge over open cavity next to valve. Hold gauge downward so solenoid plunger is against solenoid stop and rotate gauge. Adjust air bleed valve so gauge pivots over and just contacts top of valve. (Scheme 6)

Scheme 6

AIR VALVE SPRING

1. Loosen shaft lock screw using Allen wrench. Rotate spring fulcrum pin counterclockwise until throttle valves open. (Scheme 7)
2. Rotate spring fulcrum pin clockwise until throttle valves close. Then rotate spring fulcrum pin proper amount of revolutions. See CARBURETOR ADJUSTMENT SPECIFICATIONS table.
3. Hold spring fulcrum pin and tighten lock screw. Apply a light coat of grease to spring contact area.

Scheme 7

CHOKE COIL LEVER

1. Remove choke cover retaining rivets. Remove choke cover and coil assembly from choke housing. (Scheme 8) Position fast idle cam on highest step of fast idle lever.
2. Push upward on choke coil lever to close choke valve. Install a.120" (3.04 mm) drill or pin gauge in choke housing hole. (Scheme 8) Lower edge of choke lever should just contact pin gauge. Bend choke rod to adjust.

Scheme 8

CHOKE ROD (FAST IDLE CAM)

1. Install rubber band to vacuum break lever of intermediate choke shaft. (Scheme 9) Open throttle, allowing choke valve to close. Install Angle Gauge (J-26701-A) on choke valve.
2. Adjust angle gauge to choke rod specification. See CARBURETOR ADJUSTMENT SPECIFICATIONS table. Place fast idle cam on second step of cam lever.
3. If cam lever does not contact cam, adjust fast idle screw. Bend tang on fast idle assembly until angle gauge bubble is centered. (Scheme 9)

Scheme 9

PRIMARY (FRONT) VACUUM BREAK

Note. Choke coil lever and choke rod (fast idle cam) adjustments must be correct before performing this adjustment.

1. Install rubber band to vacuum break lever of intermediate choke shaft. Open throttle, allowing choke valve to close. Install Angle Gauge (J-26701-A) on choke valve. (Scheme 10)
2. Adjust angle gauge to specification. See CARBURETOR ADJUSTMENT SPECIFICATIONS table. Plug vacuum break bleed holes (if equipped).
3. Using vacuum pump, apply 15 in. Hg vacuum to vacuum break. Ensure bucking spring is seated. (Scheme 10) If air valve rod restricts vacuum break plunger from retracting, release vacuum and bend rod to allow full plunger travel.
4. Reapply vacuum and note bubble reading on angle gauge. Adjustment is correct when angle gauge bubble is centered. Adjust screw located on bucking screw to center bubble.

Scheme 10

SECONDARY (REAR) VACUUM BREAK

Note. Choke coil lever and choke rod (fast idle cam) adjustments must be correct before performing this adjustment.

1. Install rubber band to vacuum break lever of intermediate choke shaft. Open throttle, allowing choke valve to close. Install Angle Gauge (J-26701-A) on choke valve. (Scheme 11)
2. Adjust angle gauge to specification. See CARBURETOR ADJUSTMENT SPECIFICATIONS table. Plug vacuum break bleed holes (if equipped).
3. Using vacuum pump, apply 15 in. Hg vacuum to vacuum break. Ensure bucking spring is compressed (if equipped). If air valve rod restricts vacuum break plunger from retracting, release vacuum and bend rod to allow full plunger travel.
4. Reapply vacuum and note bubble reading on angle gauge. Adjustment is correct when angle gauge bubble is centered. Rotate adjusting screw located on rear of vacuum break (if equipped). On models without adjusting screw, use Linkage Adjuster (J-9789-111) while supporting rod at "S" area and bend vacuum break rod. (Scheme 11)

Scheme 11

AIR VALVE ROD - FRONT

1. Plug vacuum break bleed hole (if equipped). Using vacuum pump, apply 15 in. Hg vacuum to vacuum break. Ensure air valves are fully closed. (Scheme 12)
2. Measure clearance between rod and end of lever slot. Install a.025" (.63 mm) drill or pin gauge between rod and end of slot. (Scheme 12)
3. Bend rod at point shown to obtain a clearance of.025" (.63 mm) with vacuum applied. Remove tape and reconnect vacuum hose to diaphragm.

Scheme 12

CHOKE UNLOADER

Note. Choke coil lever and choke rod (fast idle cam) adjustments must be correct before performing this adjustment.

1. Install rubber band to vacuum break lever of intermediate choke shaft. Open throttle, allowing choke valve to close. Install Angle Gauge (J-26701-A) on choke valve. (Scheme 13)
2. Adjust angle gauge to specification. See CARBURETOR ADJUSTMENT SPECIFICATIONS table. Hold secondary lock-out lever away from pin. (Scheme 13)
3. Hold throttle lever in wide open position. Note bubble on angle gauge. Adjustment is correct when angle gauge bubble is centered. Using Linkage Adjuster (J-9789-111), adjust fast idle lever to center bubble.

Scheme 13

Lock-Out Lever Side Clearance

1. Place fast idle cam on highest step of cam lever. Hold throttle lever closed. Measure secondary throttle valve lock-out side clearance between pin and lock-out lever. (Scheme 14)
2. Lock-out lever side clearance should be.010-.020" (.25-50 mm). Adjust clearance by bending pin.

Lock-Out Lever Opening Clearance

1. Push down on tail of fast idle cam, allowing lock-out lever to move away from pin. Rotate throttle lever to position minimum clearance between lock-out lever and pin. (Scheme 14)
2. Measure specified opening clearance between end of pin and lock-out lever toe. (Scheme 14) Clearance should be.015" (.38 mm). Adjust clearance by filing end of pin.

Scheme 14

Scheme 15

1. Idle mixture screw plugs should be removed (if equipped) prior to disassembly of carburetor. Invert carburetor. Using hacksaw, saw 2 parallel cut areas in throttle body between locator points near one idle mixture plug. (Scheme 15)
2. Distance between cut areas should be near size of punch to be used for plug removal. Cut downward to the plug. Cut area should not exceed more than 1/8" beyond locator points.
3. Place flat punch near end of cut areas. Holding punch at a 45 degree angle, drive punch inward toward throttle body to break casting away. Use a center punch to break plug and expose idle mixture screw. Repeat procedure for remaining plug.

Air Horn

1. Place carburetor in Holding Fixture (J-9789-118). Remove fuel filter, spring and fuel inlet nut. Remove ILC assembly. Remove primary and secondary vacuum break assemblies and linkage (if equipped).
2. Air bleed valve cover must be removed. Seal bowl vents and air inlets with tape. Using a 7/64" drill bit, drill out head of air bleed valve cover retaining rivet.
3. Remove rivets and air bleed valve cover. Clean metal shavings from top of carburetor. Remove air bleed valve assembly. Remove "O" rings from air bleed valve.
4. Remove secondary metering rod holder retaining screw. Remove metering rod holder and metering rods. Remove choke lever retaining screw. Remove choke lever.
5. Pull upward on choke link. Hold intermediate choke lever outward while twisting choke link from lever. Remove pump link retainer at pump lever. Remove pump link from pump lever. DO NOT remove pump lever from air horn.
6. Remove air horn-to-float bowl retaining screws. Lift air horn straight up from main body. Invert air horn. Remove TPS plunger. NOTE: Use care not to damage mixture control solenoid connector, TPS adjustment lever and small tubes protruding from air horn. DO NOT attempt to remove small tubes.
7. Using small screwdriver, remove pump stem seal and TPS plunger seal retainer. Remove seals from air horn. Remove solenoid adjusting screw plug and adjusting screw (if equipped). (Scheme 16)

Float Bowl

1. Remove air horn-to-float bowl gasket. Remove mixture control solenoid plunger. Remove accelerator pump assembly. Remove spring and cup from accelerator pump.
2. Remove TPS and spring. Remove mixture control solenoid-to-air horn gasket. Remove solenoid connector retaining screws. Using Mixture Control Adjuster (J-28696-10 or BT-7928), remove solenoid mixture adjusting screw and rich limit stop.
3. Remove solenoid plunger. Remove primary metering rods and springs. Remove float bowl insert. Remove mixture control solenoid assembly. DO NOT remove plunger return spring or connector wires from solenoid.
4. Remove aneroid cavity insert. Remove solenoid return spring and adjusting screw spring. Remove float, float needle and hinge pin.
5. Using Needle Seat Remover/Installer (J-22769), remove needle seat and gasket. Using Metering Jet Remover (J-28696-4 or BT-7928), remove primary jets. CAUTION: DO NOT remove secondary jets. Secondary jets are pressed into float bowl. If jets are damaged, float bowl must be replaced.
6. Remove discharge plug retainer, discharge ball and pump well baffle. Drill out choke cover retaining rivet heads. Remove choke cover retainers. Remove choke cover, stat assembly and gasket. Remove choke housing-to-float bowl retaining screw and washer.
7. Remove choke housing. Remove choke housing-to-float bowl seal. Remove secondary throttle lock-out lever. Remove intermediate choke lever. Invert float bowl. Remove intermediate choke shaft seal.
8. Remove internal choke stat lever retaining screw. Remove choke stat lever, intermediate choke shaft, lever and link assembly and fast idle cam. Separate fast idle cam from shaft. Remove intermediate choke shaft seal.

Throttle Body

1. Using Idle Mixture Socket (J-29030-B or BT-7610B), remove idle mixture screws and springs. Note and record number of turns required for idle mixture screw removal for reassembly reference.
2. Remove throttle body-to-float bowl retaining screws. Separate throttle body and gasket from float bowl.

CLEANING & INSPECTION

1. Clean parts thoroughly in carburetor cleaner. DO NOT soak solenoids, TPS, choke cover and stat assembly, plastic, or rubber parts in cleaner. After cleaning, rinse all metal parts with HOT water.
2. Blow dry with compressed air. Choke shaft must operate freely in air horn. Inspect idle mixture screws for grooves or nicks. Replace if damaged.
3. Inspect float for damage or fuel absorption. Inspect all solenoids for damaged wiring. Using ohmmeter, check mixture control solenoid resistance. Replace solenoid if resistance is not between 20-26 ohms.
4. Check mixture control solenoid for ground. Place one ohmmeter lead on solenoid case and remaining lead on one solenoid terminal. Resistance should be infinite. Replace solenoid if grounded.
5. Pump system operation should be checked. Install new pump cup and spring on pump plunger. Install pump discharge ball, plug and pump well baffle in float bowl. Fill float chamber and pump well with clean solvent.
6. Seal 2 pump discharge passages located on top of float bowl surface. Push pump assembly downward in well area. Pump should not reach bottom of travel area. Only movement should be compression of the duration spring.
7. Excessive pump travel indicates improper seating of pump cup, worn pump well or pump discharge plug is leaking. Repair defective components.
8. Refill float chamber and pump well with clean solvent. Slowly move pump downward in pump well until solvent appears at top of pump discharge passages. Remove pump assembly and note solvent level in passages.
9. Solvent level should not decrease. If level decreases, check for missing discharge ball, improper discharge ball seating or defective ball or seat. Repair as necessary.

Float Bowl Assembly

1. Install new float bowl-to-throttle body gasket. Ensure all passages align. Install throttle body and retaining screw.
2. Install carburetor on holding fixture. Install idle mixture screws and springs. Adjust to location recorded during disassembly. Install intermediate choke shaft seal in choke housing with seal lips toward float bowl.
3. Install fast idle cam on intermediate choke shaft with stepped areas facing downward. Install cam and choke shaft in housing. Install choke stat lever on intermediate choke shaft. Install retaining screw.
4. Install choke shaft seal in float bowl with seal lips facing outward. Install choke housing seal in float bowl. Install secondary lock-out lever. Using Choke Lever Installer (J-23417), install intermediate choke lever in float bowl cavity.
5. Install choke housing assembly so intermediate choke shaft engages with intermediate choke lever. Ensure fast idle cam is located above vacuum break lever.
6. Install choke housing retaining screws. Check choke linkage for freedom of movement. Adjust choke coil lever adjustment. See CHOKE COIL LEVER under ADJUSTMENTS in this article.
7. Install pump well baffle with slot area toward bottom of float bowl. Install pump discharge ball and spring (if equipped). Install discharge ball plug. Install primary metering jets.
8. Using Needle Seat Installer (J-22769), install needle seat and gasket. Install float needle on float. Ensure float needle does not engage with slot area on float.
9. Install float hinge pin with open end facing pump well. Install float assembly. Adjust float level. See FLOAT LEVEL under ADJUSTMENTS in this article.
10. Install mixture control solenoid return spring, adjusting screw spring and aneroid cavity insert (if equipped). Install mixture control solenoid with solenoid pin aligned with float bowl hole.
11. Install solenoid retaining screw and connector-to-air horn gasket. Adjust solenoid mixture screw. See MIXTURE CONTROL SOLENOID MIXTURE SCREW under ADJUSTMENTS in this article.
12. Install float bowl insert, primary metering rods and springs. Install TPS adjusting spring and TPS. Push downward on connector to position below casting surface.
13. Install new cup and spring on accelerator pump. Install accelerator pump and spring. Install float bowl-to-air horn gasket. Install mixture control solenoid plunger.

Scheme 16

Scheme 17

1. Using Mixture Control Adjuster (J-28696-10), install TPS adjusting screw. TPS final adjustment is made after carburetor installation. Install pump stem seal and TPS seal with seal lips facing outward.
2. Install seal retainers. Stake seal retainers in 3 places. Install TPS actuator plunger. Install mixture control solenoid stop screw and spring. Using Stop Screw Adjuster (J-28696-4), lightly seat stop screw then back out 1/4 turn.
3. Hold air horn gasket downward while installing air horn. Ensure accelerator pump aligns with hole of air horn. Using small screwdriver, hold TPS adjusting lever and plunger upward while installing air horn on float bowl.
4. Ensure air horn tubes align with float bowl and gasket. Install air horn screws. Tighten screws in proper sequence. (Scheme 17)
5. Install pump link in throttle lever and pump lever. Install pump link retainer. Install choke link in intermediate choke lever while holding fast idle cam upward.
6. Install choke lever on choke link. Engage choke lever with choke shaft. Install retaining screw. Install secondary metering rods and holder. Ends of metering rods must face each other. Install holder retaining screw.
7. Operate air valves to ensure freedom of movement. Coat new "O" rings for air bleed valve with ATF. Install "O" rings on air bleed valve with thick ring in upper groove and thin ring in lower groove.
8. Install air bleed valve. Adjust air bleed valve. See AIR BLEED VALVE under ADJUSTMENTS in this article. Install and adjust vacuum break assemblies.
9. Install ILC. Install spring, fuel filter and fuel inlet nut. Tighten fuel inlet nut to 46 ft. lbs. (62 N.m). Place fast idle cam on highest step.
10. Install choke cover, stat assembly and gasket in choke housing. Ensure coil tang engages with choke stat lever and cover notch aligns with housing projection. Install choke cover retainers and rivets. Perform necessary adjustments. See ADJUSTMENTS in this article.
11. Install carburetor to intake manifold using new base gasket. Tighten bolts A-D in sequence to 12 ft. lbs. (16 N.m). (Scheme 17)