I have a 1984 ford F150 with 1 bbl carb and auto.
Need to know how mixture is controlled by fuel control solenoid on carb.
I have no oxygen sensor (junkyard motor before I owned it. I suspect this is the cause of my bad gas milage (12 mpg).

 

The solinoid on the 4.9L carb opperates by leaning
out the mixture. It gets a square wave signal from the computer that is aprox. ten pulses per second.
You can put a stethascope on the solinoid and hear it clicking at about ten cycles per second. Disconnecting the electrical connector on the solinoid will cause the fuel mixture to be rich all the time. You need an O2 sensor to let the computer know how to "dither", vary the pulse width to the solinoid to control the air-fuel mixture.