Carburetor - Driveability, Diagnosis & Repair
NUMBER 11-22-85APPLICABILITY: ALL 1982 THROUGH 1984 CARTER-WEBER EQUIPPED VEHICLES DATE 01-15-85
SUBJECT: DRIVEABILITY
-THIS SERVICE BULLETIN IS FOR INFORMATION ONLYShould you encounter a complaint of unsatisfactory driveability on 1982 through 1984 Carter-Weber carburetor equipped vehicle, first test drive the vehicle to confirm the condition. Then perform the following initial checks to ensure that all basic engine specifications were properly set during PDI or any other previous inspections. Refer to either Service Manuals MSA 115 for 1982, MSA 116 for 1983, MSA 118 for 1984, or the "Carter-Weber Service Training Manual" for the proper specifications and procedures.
NOTE: When performing services on any Carter carburetor, Torx type drivers in sizes T20, T25, T27, T50 must be used on various fasteners on the carburetor itself.
The items listed below are provided as a basic engine checklist:
1) Valve clearance
2) Ignition system operation (Checked with an oscilloscope and ohmmeter)
3) Ignition timing
4) Engine idle speed
5) Carburetor float level, metering rod adjustment, accelerator pump adjustment, etc.
6) EGR valve operation
7) Intake manifold vacuum
8) All vacuum hoses and connections
9) ECU operation
10) Accelerator cable adjustment
11) Air suction valve operation
A driveability complaint may result if any of the systems listed above are out of specification or inoperative. After checking and/or adjusting the systems as necessary, road test the vehicle to verify if a driveability condition still exists.
Should you encounter a CARTER-WEBER equipped vehicle with an unacceptable driveability condition due to a binding choke assembly, follow the procedure below to correct the symptom.
FIGURE1 - Choke Shaft Hole:
1) Disconnect the vacuum hose from the choke diaphragm and connect a hand operated vacuum pump.
2) While applying vacuum to the diaphragm, spray CRC 3-36 or the equivalent into the choke shaft hole (See Figure 1).
3) After lubricating, apply and release vacuum to the diaphragm three to four times.
4) Disconnect the hand operated vacuum pump and connect the original hose.
5) Start and warm up the engine to ensure that the choke valve opens fully.
If a complaint of "stumble" or "hesitation" during cold to normal operation still exists, then choke adjustment is necessary. To adjust the choke, a choke adjustment kit (P/N 483 537 000) must be installed, referring to the following instructions.
INDEXLOCK SET (P/N 483 537 000):
CHOKE-ADJUSTMENT
A) PARTS-REQUIRED
FIGURE2 - Choke Adjustment Procedure:
B) CHOKE ADJUSTMENT PROCEDURE
1) Remove the choke assembly from the carburetor, taking extra care not to drop anything into the intake.
2) Remove the choke heater cover by removing the three screws labeled "A, B, & C" that secure the choke heater cover to the choke housing (See Figure 2) according to the following procedure:
NOTE: When removing the three screws securing the choke heater cover to the choke housing, extra care must be taken in order not to damage the heater harness, fast idle diaphragm, the choke heater plate, or the choke heater cover.
a) File flat the top of the screws labeled "A, B, & C".
b) Using a sharp chisel and a hammer slot the three screws.
c) Remove the screws with a straight screwdriver.
FIGURE 3 - Choke Heater Cover:
3) Reinstall the choke heater cover with the new parts, according to the procedure below.
a) Install a new gasket between the choke heater cover and choke housing (See Figure 3).
b) Insert the choke lever into the hook at the end of the bi-metallic spring when installing the choke heater cover onto the choke housing.
c) Fit the tab of the choke index lock into the groove of the choke heater cover.
d) Line up the hole located under the choke index lock with the threaded hole for screw "B" (See Figure 3).
e) Install the choke index lock.
f) Install the choke heater plate.
f) Without twisting them off, install the three twist-off screws and snug them evenly.
4) Install the choke assembly onto the carburetor.
5) Road test the vehicle to confirm that the condition has been corrected.
6) If after road testing the vehicle, the conditions have not changed, remove the three twist-off screws in the choke heater.
7) Internally inspect the choke assembly to ensure that the choke heater cover and the choke heater coil have been properly installed.
8) Reassemble the choke heater using the three twist-off screws and turn them in until they twist off.
Choke assembly lubrication and choke adjustment are covered under operation #411-201 & #415-211 with the given allowance of 0.4 hrs. and during the warranty period can be claimed on an MSA 400.