Carburetor - Mikuni 2-bbl Dodge Ram I

COMPONENT TESTING

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

DESCRIPTION

Mikuni 30-32 DIDEF carburetor is used on Colt models. The 32-35 DIDEF is used on all other models. These 2-barrel, 2-stage carburetors use primary and secondary circuits. Carburetor components include conventional accelerator pump, vacuum-actuated secondary throttle diaphragm, sub-EGR valve system, fully automatic choke, coasting air valve, fuel cut-off solenoid anti-overfill device, air switching valve, bowl vent valve and dashpot.

1.5L MODELS

MIKUNI CARBURETOR IDENTIFICATION (1.5L MODELS)

2.0L MODELS

MIKUNI CARBURETOR IDENTIFICATION (2.0L MODELS)

2.6L MODELS

MIKUNI CARBURETOR IDENTIFICATION (2.6L MODELS)

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article, see Tune-Up article in TUNE-UP section.

FACTORY ADJUSTMENTS ONLY

The automatic choke, choke breaker (vacuum kick), fast idle, secondary throttle opener, accelerator pump and sub-EGR valve have all been factory-calibrated. DO NOT change any of these adjustments for any reason.

Scheme 42

1. Invert float chamber cover assembly without gasket. Using a universal float level gauge, measure distance from bottom of float to surface of float chamber cover. Distance should be.748-.826" (19-21 mm). (Scheme 42) (Scheme 42): Checking Float Level of Mikuni Carburetor
2. If float level is not within specified range, adjust by increasing or decreasing the number or thickness of needle valve shims. Adding or subtracting a shim will change fuel level about 3 times the thickness of the shim.
3. Adding shims lowers float level. Shims are available in a set of 3 thicknesses:.012" (0.3 mm),.016" (0.4 mm) and.020" (0.5 mm).
4. To install shim, remove the float, needle and needle seat. Check filter for clogging or damage. Install new "O" ring to needle seat. Install shim and filter to needle seat. (Scheme 43) Install assembly into float chamber cover.
5. Install seat retainer. Tighten screws firmly. Insert needle into seat. Install float. Recheck float level using procedure in step 1).

Scheme 43

Raider

1. Warm engine to normal operating temperature. Slide accelerator cable holder to the position at which throttle lever will begin to operate.
2. Check that inner cable has no more than.04" (1 mm) of free play. After adjustment, operate accelerator pedal to ensure that throttle valve operates smoothly from fully closed to fully opened position. (Scheme 44)

Scheme 44

All Other Models

1. With engine at normal operating temperature, adjust accelerator cable. Loosen lock nut and adjusting nut. Remove any sharp bends from cable.
2. Turn adjusting nut to a point where throttle lever just starts to move. Then back nut off 1/2 turn. Secure with lock nut. (Scheme 45) After adjustment, operate accelerator pedal to ensure throttle valve operates smoothly from fully closed to fully opened position.

Scheme 45

Scheme 46

Note. DO NOT invert carburetor during disassembly. On Colt models, DO NOT remove choke valves, choke levers and related parts, round nut from accelerator pump link, adjusting screws (except idle speed, idle mixture and dashpot), or throttle valves.

Scheme 47

1. Disconnect water hose from throttle body and choke chamber. Grind heads off choke cover lock screws. Remove cover. Disconnect ground wire from fuel cut-off solenoid at cover assembly (if equipped).
2. Remove throttle return and damper springs. Remove vacuum hose from depression chamber and throttle body. Remove accelerator pump rod from throttle lever.
3. On Colt models, remove dashpot/idle up actuator rod (man trans.) or idle up actuator rod (auto. trans.) from free lever. On Ram-50 models, remove dashpot rod from free lever. Remove actuator.
4. On Colt models, remove the deceleration, enrichment and jet mixture solenoid valves. On all models, remove depression chamber rod from secondary throttle lever.Remove the depression chamber. (Scheme 47)
5. Remove 2 long float chamber cover screws. Remove throttle body. (Scheme 48) Remove 4 short screws, and float chamber cover from main body. Remove check weight and ball, and steel ball of anti-overfill device.
6. On all models except Colt remove "E" ring from lower end of choke unloader rod. Disconnect rod from lever. DO NOT remove various devices (especially the automatic choke system) from float chamber cover unless necessary.
7. On all models, remove float pin and float. Remove screw, retainer and needle valve. On all models except Colt remove decelerator pump and fuel cut-off solenoid. DO NOT remove throttle valves or other parts unless absolutely necessary. DO NOT move adjusting screws.
8. On Colt models, remove main jets from jet blocks. Using a screwdriver, remove pilot jet retainer and pilot jet. Remove accelerator pump mounting screws, pump cover and link assembly, diaphragm, spring, body and gasket from main body.
9. Remove snap ring from sub-EGR control valve pin. Remove pin and link from valve. Remove small steel ball and spring from sub-EGR control valve. Remove sub-EGR valve from throttle body.

Scheme 48

Note. DO NOT immerse synthetic parts, electrical components or diaphragm assemblies in carburetor cleaner.

Cleaning & Inspection

1. Clean all parts with soft brush and solvent. Check throttle valve and choke valve shafts for proper operation. If not operating properly, clean and lubricate.
2. Check jets for damage or clogging. Clean with compressed air. Never use wire or other metal objects. Check idle mixture adjusting screw for grooves, ridges or other damage.
3. Check needle valve assembly, strainer screen and vacuum chamber. Check fuel cut-off solenoid operation using battery voltage. Needle should move in when solenoid is attached to battery. Needle should move out when disconnected.
4. Thoroughly inspect carburetor main body, throttle body and float chamber cover for cracks or other damage. Apply vacuum to diaphragms. Check for leakage.

Reassembly

1. To reassemble, reverse disassembly procedure. Ensure that all air and fuel passages are clear. Lubricate linkage after cleaning. Check throttle and choke linkage for smooth operation.
2. Be sure that sub-EGR valve is operating smoothly. If a main or pilot jet needs to be replaced, make sure that replacement jet is of the same size. A number is stamped on each jet.
3. To prevent carburetor-to-intake manifold gasket from being installed incorrectly, match holes of gasket to throttle body. Place gasket on intake manifold.

Note. For specifications, see ADJUSTMENTS in this article.

Removal

1. Turn the crankshaft to place No. 1 cylinder at top dead center on compression stroker. NOTE: The above operation places the lift of the fuel pump stroke at the minimum position, resulting in ease of fuel pump removal.
2. On vehicles with 2.6L engine, if interference of pump lever occurs in the cylinder head, the washer on the cylinder head bolt may be interfering with the pump lever. Therefore, proceed as follows: Remove the rocker cover. Loosen cylinder head bolts in sequence (Scheme 49) Move the washer interfering with the pump lever in the direction (Scheme 49)and remove the fuel pump.

Cylinder Head Bolt Sequence. Scheme 49

Inspection

Make the following checks and replace as necessary. Note that the fuel pump is a non-maintainable assembly and must be replaced as an assembly.

1. Oil or fuel leaks from breather hole or pipe.
2. Damage, cracks on parts.
3. Rocker arm for wear.

Push Rod (2.0L)

Insert push rod into cylinder head hole to make sure that it slides smoothly with no excessive play.

Service Points Of Installation (Eng. Oil To Push Rod Application 2.0L)

Apply engine oil to the periphery of the push rod before it is inserted in the cylinder head.

Installation

1. Make sure that piston in No. 1 cylinder is in the top dead center on compression stroke.
2. If the washer is moved after loosening of cylinder head bolt on 2.6L engine equipped vehicles, proceed to the following items: Reinstall the washer in position. Tighten the cylinder head bolts to specified torque in (Scheme 50) or (Scheme 51). Install rocker cover.

Fuel Pump Exploded View (2.0L). Scheme 50

Fuel Pump Exploded View (2.6L). Scheme 51

SPECIFICATIONS

Note. For specifications, see ADJUSTMENTS in this article. For reference view of components (Scheme 50)or (Scheme 51).

See also:
• ADJUSTMENTS
• OVERHAUL