Carburetor - Rochester 2se & e2se 2-bbl GMC Vandura I

COMPONENT TESTING

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

APPLICATION

Note. SERIES IDENTIFICATION: The vehicle numbers used in this article have been abbreviated for common reference to both Chevrolet and GMC models. Chevrolet models use numerical designations as listed; GMC models are identified as follows: 10 = 1500; 20 = 2500; 30 = 3500. References to the Chevrolet S10 also apply to the GMC S15.

2.0L 4-CYLINDER CARBURETOR APPLICATIONS

2.0L 4-CYLINDER CHEVROLET & GMC (ROCHESTER) CARBURETOR NO.

2.8L V6 CARBURETOR APPLICATIONS

2.8L V6 CHEVROLET & GMC (ROCHESTER) CARBURETOR NO.

4.1L 6-CYLINDER CARBURETOR APPLICATIONS

4.1L 6-CYLINDER CHEVROLET & GMC (ROCHESTER) CARBURETOR NO.

IDENTIFICATION

The Rochester 2SE and E2SE carburetor numbers are stamped vertically on the float bowl, next to the vacuum tube. If float bowl is replaced, follow manufacturer's instructions contained in service package to transfer part number to new float bowl. (Scheme 56)

Carburetor Part Number Location. Scheme 56

DESCRIPTION

The Rochester 2SE and E2SE are 2-stage, 2-barrel downdraft carburetors. The primary stage consists of a triple venturi with a 35 mm bore.

The secondary stage has a 46 mm bore and is equipped with an air valve with a single tapered metering rod. Both are equipped with integral electronically-activated chokes, a choke vacuum break diaphragm, and an idle speed solenoid.

The E2SE model is used in conjunction with the Chevrolet/GMC Computer Command Control (CCC) system.

The E2SE model is equipped with an electrically-actuated mixture control solenoid mounted in the air horn. Fuel metering is controlled by the mixture control solenoid plunger, which opens and closes in response to signals from the on-board computer.

This opening and closing action causes a variable restriction of fuel to the main metering circuit, changing air/fuel ratio. Also, air metered to the idle system is controlled by the movement of the mixture control solenoid plunger.

The solenoid is activated by an electronic signal from the Electronic Control Module (ECM). The ECM responds to a signal from the oxygen sensor in the exhaust. When energized, the solenoid moves the plunger down to a lean position. When de-energized, the solenoid moves the plunger up to a rich position.

Air metered (by the solenoid plunger) to the idle system is controlled by an idle air bleed valve located in the air horn. This valve follows movement of the mixture control solenoid.

On E2SE models, a Throttle Position Sensor (TPS) is used to signal the ECM of throttle position changes as they occur. When throttle position is changed, a tang on the pump lever moves the TPS plunger. This signals the ECM to hold the last known air/fuel ratio to aid in throttle response.

ADJUSTMENT

Note. For all on-vehicle adjustments, see TUNE-UP SERVICE PROCEDURES.

ANGLE GAUGE ADJUSTMENT TOOL

Manufacturer recommends that some carburetor adjustments be performed using a choke valve angle gauge (Kent-Moore tool no. J-26701). While preparations and actual adjustments may vary with each individual adjustment, the procedure for using the angle gauge to check the choke valve angle remains the same. Use the following procedure to perform adjustments requiring the use of the choke angle gauge.

1. Rotate degree scale on angle gauge so that 0° mark is opposite pointer.
2. With choke valve closed, place angle gauge magnet squarely on choke valve. Rotate leveling bubble on angle gauge until it is centered. Rotate degree scale until specified degree mark is opposite pointer. (Scheme 57)
3. Perform individual adjustment preparations as outlined in the following carburetor adjustments requiring angle gauge. If bubble is centered, adjustment is correct. If not, adjust carburetor as outlined.

Choke Valve Angle Gauge. Scheme 57

FLOAT LEVEL

1. Remove air horn and gasket from float bowl. Hold float retainer down firmly, while lightly pushing float down against needle. (Scheme 58)
2. Position a "T" scale over toe of float at point furthest away from float hinge. Measure distance from float bowl casting to float.
3. To adjust, remove float, and bend float arm. Check to make sure float is correctly aligned after adjustment.

Float Level Adjustment. Scheme 58

CHOKE COIL LEVER

Note. Choke coil cover is retained on housing with rivets to prevent tampering with adjustment. If necessary to remove cover, refer to Overhaul procedures in this article. If rivets and cover are removed, a choke cover retainer kit is required for reassembly.

1. Remove choke thermostatic cover from choke housing. Place fast idle speed screw on high step of fast idle cam. Push on intermediate choke lever until choke valve is fully closed.
2. Insert specified drill or pin gauge in hole provided in choke housing. Edge of choke lever (inside housing) should just touch drill or pin gauge. (Scheme 59)
3. To adjust, bend intermediate choke rod at point shown in Fig. (Scheme 59). Reinstall choke cover, and adjust.

Choke Coil Lever Adjustment. Scheme 59

CHOKE ROD (FAST IDLE CAM)

Note. Before adjusting choke rod, choke coil lever adjustment must be correct and fast idle adjustment must be made. Use angle gauge adjustment tool to perform adjustments. See Angle Gauge Adjustment Tool at beginning of Adjustments.

1. Place fast idle speed screw on 2nd step of fast idle cam, against shoulder of highest step.
2. Close choke valve by lightly pushing on intermediate choke lever. Hold in place with rubber band. Push vacuum break lever toward open choke position, until lever is against rear tang on choke lever. (Scheme 60)
3. Bubble on choke angle gauge should be centered, with specified degree mark opposite pointer.
4. To adjust, bend fast idle cam rod at point shown in Fig. (Scheme 60) until bubble is centered in angle gauge.

Choke Rod (Fast Idle Cam) Adjustment Close. Scheme 60

AIR VALVE ROD

Note. This adjustment is made by using the choke valve angle gauge. See procedure at beginning of Adjustments.

1. Using an outside vacuum source of at least 15 in. Hg, seat primary choke vacuum break diaphragm. If purge bleed hole is used, plug end cover with masking tape or accelerator pump plunger cup. Close air valve, then mount and adjust angle gauge. (Scheme 61)
2. Apply light opening pressure to air valve shaft. Set to specified angle by bending air valve rod until angle gauge bubble is centered. Remove masking tape, if used.

Air Valve Rod Adjustment. Scheme 61

AIR VALVE SPRING

1. Using an Allen wrench, loosen lock screw. Turn tension adjusting screw clockwise until air valve partially opens. (Scheme 62)
2. Turn tension adjusting screw counterclockwise, until air valve just closes. Turn screw counterclockwise 1 (1 1/4 turns on 2.0L carburetors or 1/2 turn on carburetor No. 17083650) additional turn. Tighten lock screw.
3. Lubricate contact area of air valve shaft pin and closing spring with lithium base grease.

Air Valve Spring Adjustment. Scheme 62

PRIMARY VACUUM BREAK

Note. This adjustment is performed using the choke valve angle gauge. See procedure at beginning of Adjustments.

1. Attach a rubber band to intermediate choke lever. Open throttle to allow choke valve to close. Set up angle gauge and set to specification. Using an outside vacuum source of at least 18 in. Hg, seat primary choke vacuum break diaphragm. On models with air bleed, plug air bleed hole to maintain vacuum.
2. Air valve rod must not restrict plunger from retracting fully. If necessary, bend air valve rod to permit full plunger travel. If equipped with bucking spring, plunger stem must be at full extent of travel to compress spring. Bubble on choke valve angle gauge should be centered with specified degree mark opposite pointer. (Scheme 63)
3. To adjust, bend rod at location shown in Fig. (Scheme 63) until bubble of angle gauge is centered OR use a 1/8" Allen wrench to turn diaphragm screw in or out until bubble of angle gauge is centered. Perform either adjustment with vacuum still applied. Apply a bead of sealer over screw to seal adjustment.

Primary Vacuum Break Adjustment. Scheme 63

SECONDARY VACUUM BREAK

Note. This adjustment is made using the choke valve angle gauge. See procedure at beginning of Adjustments.

1. Attach a rubber band to intermediate choke lever. Open throttle to allow choke valve to close. Set up angle gauge and set to specification. Using an outside vacuum source of at least 18 in. Hg, seat primary choke vacuum break diaphragm. On models with air bleed, plug air bleed hole to maintain vacuum.
2. If equipped with bucking spring, plunger stem must be at full extent of travel to compress spring. Bubble on choke valve angle gauge should be centered with specified degree mark opposite pointer. (Scheme 64)
3. To adjust, bend rod at location shown in Fig. (Scheme 64) until bubble of angle gauge is centered OR use a 1/8" Allen wrench to turn diaphragm screw in or out until bubble of angle gauge is centered. Perform either adjustment with vacuum still applied. Apply a bead of sealer over screw to seal adjustment.

Secondary Vacuum Break Adjustment. Scheme 64

AUTOMATIC CHOKE

Note. Choke coil cover is retained on housing with rivets to prevent tampering with factory adjustment. If necessary to remove cover, refer to Disassembly and Reassembly procedures in this Section.

CHOKE UNLOADER

Note. This adjustment is performed using the choke valve angle gauge. See procedure at beginning of Adjustments.

1. Attach a rubber band to intermediate choke lever. Open throttle to allow choke to close fully. Set angle gauge to specifications.
2. Hold primary throttle valve wide open. Push on choke shaft lever to open choke and to make contact with Black closing tang. To adjust, bend tang on throttle lever until bubble in angle gauge is centered. (Scheme 65)

Choke Unloader Adjustment. Scheme 65

SECONDARY LOCKOUT

1. Hold choke valve wide open by pushing counterclockwise on choke intermediate lever. Open throttle valves until end of secondary actuating lever is opposite toe of lockout lever.
2. Measure specified clearance between end of actuating lever and toe of lockout lever. Measurement can be checked using a drill or pin gauge of specified size. To adjust, bend lockout lever tang contacting fast idle cam. (Scheme 66)

Secondary Throttle Lockout Adjustment. Scheme 66

DISASSEMBLY

Note. Before disassembling carburetor, mount unit in a suitable holding fixture to prevent damage to throttle valves or linkage.

Air Horn

1. Remove hose from vacuum break assembly or assemblies. Remove vacuum break and idle speed solenoid bracket attaching screws from air horn. Rotate vacuum break and bracket assembly to disengage vacuum break link (T-pin) from slot in vacuum break lever, and air valve rod from slot in air valve lever.
2. Remove secondary vacuum break bracket assembly attaching screws from throttle body (if equipped). Rotate bracket to remove vacuum break link from vacuum break lever slot. Remove clip from hole in accelerator pump rod. NOTE: DO NOT remove pump lever retaining screw. Pump lever and washer must not be removed from air horn assembly.
3. If necessary to remove air valve rod from vacuum break, remove and discard retaining clip from end of air valve. New retaining clip must be used on reassembly. Plastic bushing used on rod may be reused.
4. Remove and discard retaining clip from intermediate choke rod at choke lever. Use a new retaining clip at reassembly. Remove plastic choke rod and bushing from choke lever. Bushing may be reused.
5. If equipped, remove hot idle compensator valve screws. Remove valve and seal from air horn, discard seal. Valve removal is necessary to gain access to short air horn-to-bowl attaching screw.
6. On E2SE models, remove 3 mixture control solenoid screws, and remove mixture control solenoid using a light twisting motion. Remove and discard solenoid gasket, plunger seal and plunger seal retainer. Retain spacer for use during reassembly.
7. Remove air horn-to-float bowl screws and lock washers. Remove vent and screen assembly. Rotate fast idle cam to full "UP" (12 o'clock) position. Remove air horn assembly by tilting to disengage fast idle cam rod from slot in fast idle cam and pump rod from hole in pump lever.
8. Disconnect fast idle cam rod from choke lever by aligning tang on rod with slot in lever. Remove from air horn assembly.
9. On E2SE models, remove TPS plunger by pushing through seal in air horn. Remove seal retainer and seal. Remove accelerator pump plunger seal from air horn. NOTE: To prevent damage to sealing surface, use fingers only (no tools) when removing plunger. To prevent damage to air horn, use care in removing plunger seal retainer and plunger stem seal retainer. Discard seals and retainers.
10. It is not necessary to remove choke valve and shaft unless they are bent or damaged. Choke valve screws are staked in place. Staking must be removed before screws are removed.

Note. DO NOT remove plugs covering idle air bleed screw during routine service. This adjustment is factory-set, and no attempt should be made to change the adjustment, unless air horn or float bowl is replaced.

Exploded View of Rochester Model 2SE Carburetor. Scheme 67

Exploded View of Rochester Model E2SE Carburetor. Scheme 68

Float Bowl

1. Remove air horn gasket. Remove pump plunger and pump spring from pump well. Remove plastic filler block from float valve. Remove float assembly and float valve by pulling up on retaining pin.
2. Remove float needle seat, gasket and extended metering jet from float bowl. Use a jet tool (J-22769) or screwdriver that fully fits slot in top of jet. DO NOT remove or change adjustment of screw located deep inside the metering jet (if equipped).
3. On E2SE models, push up from bottom on electrical connector and remove TPS and connector from float bowl. Remove spring from bottom of TPS well in bowl.
4. On 2SE models, press down on power piston stem and allow it to snap up. Repeat this until plastic retainer is dislodged. Remove power piston and metering rod assembly. DO NOT remove power piston by using pliers on metering rod holder.
5. Remove spring from power piston bore. If necessary to remove metering rod from hanger, compress spring on metering rod and align groove on rod with slot in holder. Care must be taken not to damage tip of metering rod.
6. Remove main metering jet using a screwdriver that fits tight in groove. On all models, use a small slide hammer to remove plastic retainer holding pump discharge spring and check ball in place in float bowl. Discard retainer. Turn float bowl upside-down and catch pump discharge spring and check ball. NOTE: DO NOT attempt to remove retainer by prying out with a screwdriver or punch. Any damage to sealing beads on bowl casting surface requires replacement of float bowl assembly.
7. If necessary to remove tamper-resistant choke cover and coil assembly, align a .159" (No. 21) drill on choke cover retaining rivets. Drill only enough to remove rivet heads. Remove rivets, choke cover and coil assembly.
8. Remove screw from end of intermediate choke shaft in choke housing. Remove choke coil lever from shaft. Slide intermediate choke shaft out of float bowl. Remove choke housing screws and remove choke housing.
9. Remove fuel inlet nut with gasket. Remove check valve/filter and spring. Discard gasket and filter. Remove 4 screws securing throttle body to float bowl. Remove throttle body. Remove throttle body insulator gasket.

Throttle Body

1. Hold throttle valves wide open. Disengage pump rod from throttle lever by rotating rod until tang on rod aligns with slot in lever.
2. DO NOT remove plug covering idle mixture screw unless it is necessary to replace mixture screw or normal soaking and air pressure fails to clean idle mixture passages. Remove curb idle and fast idle speed screws and springs if necessary. NOTE: Further disassembly of throttle body is not required. Throttle valve screws are permanently staked. DO NOT remove idle mixture screw plug unless necessary to replace mixture screw or cleaning and air pressure fails to clean idle mixture passage. If necessary to remove, proceed as follows
3. Invert throttle body and position on a holding fixture with manifold side up. Using a small hacksaw, make 2 small cuts, one on either side of mixture screw plug location. Position a small flat punch on throttle body between cuts.
4. Drive punch down and break out portion of throttle body between the 2 cuts. Hold punch at a 45° angle and drive out hardened steel plug. Plug will shatter when struck. Remove loose pieces to allow the use of adjusting tool (J-29030 or equivalent) to remove adjusting screw and spring.
5. Turn mixture screw in carefully, counting turns needed to seat screw. Record number of turns for reassembly reference. Remove mixture screw.

CLEANING & INSPECTION

1. Use a regular carburetor cleaning solution. Soak components long enough to thoroughly clean all surfaces and passages of foreign matter.
2. DO NOT soak any components containing rubber, leather or plastic. Definitely do not soak idle speed solenoid or control mixture control solenoid, throttle position sensor, electric choke, diaphragms, pump plunger and plastic filler block. Plastic bushings in end of vacuum break link and air valve rod will withstand normal cleaning.
3. Remove any residue after cleaning by rinsing components in a suitable solvent.
4. Blow out all passages with dry compressed air.

REASSEMBLY

Use new gaskets and seals. Make sure new gaskets fit correctly and all holes are punched through and properly located. To reassemble carburetor, reverse disassembly procedure and note the following

1. Install fuel inlet needle pull clip over edge of flat on float arm facing float. DO NOT hook clip in holes in float arm.
2. After throttle body is installed on float bowl, make sure secondary lockout tang is in correct position to engage secondary lockout lever.
3. Install new accelerator pump discharge check ball, spring and plastic retainer. Insert end of retainer in spring and place in position in float bowl. Lightly tap retainer into position until it is flush in float bowl.
4. Make sure holes in fuel filter face toward fuel inlet fitting when filter is installed. This will ensure that check valve end of filter is installed properly.
5. Some linkage retaining clips are dished. Make sure portion of clip that bends outward is toward end of rod. Make sure clip makes full contact with rod.
6. Place fast idle screw on high step of fast idle cam. Install choke coil cover, aligning notch in cover with raised boss on housing cover flange. If choke cover and coil assembly was removed from housing, a service rivet kit must be used to restore tamper-resistant feature.
7. On E2SE models, be sure coil pick-up lever is located inside choke coil tang. On electric chokes, the ground contact is provided by a metal plate at rear of choke cover assembly. DO NOT install a choke cover gasket between electric choke assembly and choke housing.
8. Install air horn screws, noting location and type of screw for correct installation. Tighten all screws evenly, securely and in sequence. (Scheme 69)
9. On E2SE models, install mixture control solenoid seal on solenoid stem. Using a 3/16" socket and hammer, lightly tap retainer in place on stem. Leave a slight clearance between retainer and seal. Apply silicone grease to seal before installation of solenoid.

Air Horn Screw Location and Tightening Sequence. Scheme 69

2SE CARBURETOR

2SE CARBURETOR ADJUSTMENT SPECIFICATIONS

E2SE CARBURETOR

E2SE CARBURETOR ADJUSTMENT SPECIFICATIONS