Carburetor - Diagnostics/Servicing
84ford7Article No. 84-19-7
CARBURETOR - DIAGNOSTIC/SERVICING (3.8L WITH 2150 CARBURETOR)
FORD 1984 LTD
LINCOLN-MERCURY 1984 MARQUIS
CALIBRATION: 4-14B-R11
Some 1984 LTD/Marquis vehicles were built with the 2150-2V carburetor which incorporates altitude compensation for fuel and spark. This article outlines diagnostic and servicing instructions.
Figure 10:
The 4-14B-R11 (3.8L 2V, 49 States, C5 LTD/Marquis) calibration incorporates altitude compensation for fuel and spark. Three components are used to accomplish this compensation; the carburetor altitude compensator, the UIC ignition module, and the barometric pressure switch. Service and diagnostic information for these components are shown below (Refer to Figure 10):
Altitude Fuel/Air Ratio Compensation
The altitude compensator, located on the back of the carburetor, is a two-position (open or closed) device. When open, it reduces fuel flow by bleeding air into the carburetor main and idle circuits. The carburetor is the same type as 2150A feedback carburetor except the feedback motor is used as an altitude compensator only.
The altitude compensator is activated by a barometric switch whose switch point is approximately 3,500 ft. Below the switch point no power is applied to the compensator. Above the switch point, battery voltage is applied to the compensator with the ignition switch on.
Service Information
A. Below 3,500 ft.
The altitude compensator should be closed, that is, no power applied to the compensator with the ignition switch on. If power is present at the compensator, replace the barometric switch.
B. Above 3,500 ft. The altitude compensator should be open, that is, power should be applied to the compensator with the ignition switch on.
If power is not present at the compensator, check for power to the barometric switch. If power is
available to barometric switch but not to the compensator, replace the barometric switch.
C. Operational Check of Altitude Compensator Power must be applied to the compensator - below 3,500 ft. this must be done artificially by removing the connector from the rear of the compensator on the rear of the carburetor and applying a battery voltage to one spade connector and grounding the other. When power is applied or removed, an audible "click" should be heard. Below 3,000 ft. with power applied to the compensator, the engine should idle and run rough. Above 3,000 ft. engine idle and run characteristics may not change significantly as compensator is opened and closed.
The compensator should be replaced if the "click" is not heard when power is applied and removed.
Altitude Spark Compensation The UIC ignition module allows the ignition timing to increase by 4~ above 3,500 ft. The UIC is activated by the same barometric switch that activated the carburetor altitude compensator. The barometric switch is closed above 3,500 ft.
Operational Check & Setting Timing Unplug the connector joining the barometric switch and the UIC module. Connect a jumper across the two spade connectors of the UIC. The ignition timing should be 12~ BTDC with jumper in place. With jumper removed and the UIC not connected to the barometric switch, the ignition timing should go to 8~ BTDC. When the UIC to barometric switch connectors are joined, the timing should go to 12~ BTDC above 3,500 ft. and remain at 8~ BTDC below 3,500 ft.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: "INFORMATION ONLY"