Fuel Control
Some 3.7L models are equipped with a Holley 6145 1-barrel feedback carburetor. Some 3.9L and 5.2L models are equipped with a Holley 6280 2-barrel feedback carburetor. These carburetors contain an electronically operated duty cycle solenoid. This solenoid meters air flow of the carburetor fuel circuit and operates in parallel with the conventional fixed main metering jets. The computer controls the operation of the solenoid with electrical signals, in response to input from data sensors. See Fig 1 .
When the solenoid is de-energized by the computer, the solenoid valve spring pushes upward through the main system fuel valve. When de-energized, the solenoid main metering orifice is fully uncovered, providing the richest mixture for any given air flow.
When the solenoid is energized by the computer, the solenoid main metering orifice is fully sealed. This solenoid position offers the leanest mixture within the carburetor for any given air flow.
Main system fuel may be regulated between richest and leanest mixture conditions by controlling the amount of time that the solenoid is energized and de-energized. The computer controls the length of time that the solenoid is energized relative to total solenoid operation time.
This time interval is determined by engine operating conditions and/or oxygen sensor signals. In this manner, the ideal air/fuel ratio can be constantly maintained.