Carburetor - 2150-2V Diagnostic/Service

Article No. 85-17-4

CARBURETOR (2150-2V) - VEHICLES WITH 3.8L ENGINE
- DIAGNOSTIC/SERVICE INFORMATION

FORD 1984 LTD

LINCOLN-MERCURY 1984 MARQUIS

CALIBRATION: 4-14B-R11

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.

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.

Figure 2 - Carburetor - Diagnostic Information:

The altitude compensator is activated by a barometric switch whose switch point is approximately 3500 ft. Below the switch point, the circuit is broken by the barometric switch. Above the switch point, the barometric switch closes the circuit. Power is always applied at the altitude compensator. Power flow is at the compensator, through the barometric switch and then to ground (see Figure 2).
Service Information

A. Below 3500 ft.

The barometric pressure switch should be open, that is, no voltage should be present at the ground side of the barometric pressure switch with the ignition switch on. If voltage is present between the barometric pressure switch and ground, replace the barometric pressure switch.
B. Above 3500 ft.

The barometric pressure switch should be closed, that is, voltage should be present at the ground side of the barometric pressure switch with the ignition switch on. If voltage is not present between the barometric pressure switch and ground, and voltage is present between the altitude compensator and ground, replace the barometric pressure switch.

C. Operational Check of Altitude Compensator

Power must be applied to the compensator - below 3500 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 turned on and off an audible "click" should be heard. Below 3000 ft. with power applied to the compensator, the engine should idle and run rough. Above 3000 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 turned on and off.

Altitude Spark Compensation

The UIC ignition module allows the ignition timing to increase to 4~ above 3500 ft. The UIC is activated by the same barometric switch that activated the carburetor altitude compensator. The barometric switch is closed above 3500 ft.

Operational Check and Setting Time

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 l2~ BTDC above 3500 ft. and remain at 8~ BTDC below 3500 ft.

OTHER APPLICABLE ARTICLES: Supercedes 84-19-7
WARRANTY STATUS: "INFORMATION ONLY"