The 2.3l Lima engine was introduced in the 1970s and was built to 1997
Originally came with a carb, upgraded to electronic fuel injection in 1985
The turbo was introduced in 1979 and had a carb only. Somewhere in 1983/1984 model year the SVO version got fuel injection for Mustangs and Thunderbirds. Some of these SVO 2.3l 4 cylinder SVO engines had 2 spark plugs per cylinder.
A carb is not going to have a return fuel line. Electronic fuel injection will have a return line. With that said you are posting in the Fairmont Forum. While the 2.3 turbo was an option for Fairmont, that engine with a turbo had a carburetor. And it was a one or two year option for Fairmont. Fairmont was discontinued at the 1983 model year. I do not believe Fairmont ever had electronic fuel injection.
What model year Fairmont do you have?
Is the engine stock? If no where did the engine come from?
OK I saw your avatar and it answers a question of mine
Your Fairmont is 1979. The 2.3l engine for 1979/1980 could be had with a non-intercooled turbo. Equipped with 2 barrel carb. The Fairmont Futura Turbo model had this engine. Again that engine in Fairmont was confined 79 or 80. No other years.
Fuel injection was not available on 2.3l until model year 1983, and only in Thunderbird Turbo Coupe and Mustang Turbo GT.
Not sure how you have a return line on your 1979 Fairmont engine or fuel pump unless the engine is a 1983 or later engine. The 1979 Fairmont tank will not have a fitting to accept returned fuel. You will have to fabricate that if you want to use a fuel injected engine.