My72Cutlass

I have a 1972 Cutlass Oldsmobile 2 door hard top, When I removed the body from the frame I only seen 2 fuel lines running down the passenger side of the frame...... I now dont know if it was the main fuel line and vapor line OR the main fuel line and fuel return line..... my gas tank has 4 ports, 1 that is from the sending unit...... So I guess my question is did the 72 cutlass with the 1 port from the sending unit come with a fuel return or not...... Thank You Guys!!!!!

2blu442

Welcome to the site! I can't answer your question off the top of my head. I've got hardcopies of the 1970 & 71 Chassis Service Manuals, but am not sure if 1972 did something different than 1971. Have you checked out wildaboutcars.com yet? Membership is free and you can download electronic copies of the Service Manuals. The Chassis Service Manuals have a lot of good information and I'm pretty sure they will have a diagram showing the routing of fuel and vapor lines.


John

joe_padavano

If you only have two lines, the large one is the main suction line from the tank to the pump and the second line is the vapor line that goes to the charcoal canister. Cars with A/C or high output engines had a third line that was the fuel return line, but base model cars usually did not get this one. If your car had fuel return, your tank sending unit would have had two lines going to it. The other lines to the tank are vent lines that go to the charcoal canister.

My72Cutlass

Thanks guys for the helpfull advice, I do have a build or owners manual to my 1972 Cutlass, I did find the diagram to show me how the fuel lines and vapor lines are ran.... And do see that in my car there is only 1 fuel line and a vapor line..... but now my question to Joe Padavano is : I do have ac in the car, and out of the sending unit there is only 1 port..... So im guessing its probably just the 1 fuel line and 1 vapor line..... now if I decide to change the sending unit to have 2 ports 1 for the main fuel and one for the fuel return due to I want to rebuiuld/overhaul my engine can this be done???..... What exactly do I want to do to the engine I dont know yet, but I do know I want more horsepower, I want both tires to squeel like 2 little pigs....lol

joe_padavano

Sorry, I missed the fact that you have a 72. There's documentation that some 72s with A/C did not use fuel return. The reason for fuel return is that by circulating part of the fuel back to the tank, percolation in the carb due to high underhood temperatures (due to loads like A/C or a high perf engine) is minimized since the fuel is constantly circulated in the lines. This is sort of the opposite of the systems they sell to circulate hot water in your house so you don't need to wait for the water to warm up when you turn on the shower.

In any case, the use of fuel return or not is unrelated to what you do to the engine. I think it's always better to run fuel return, especially with today's ethanol-loaded gas that is even more susceptible to percolation, but all that needs to change (in addition to the tank sender) is the fuel pump.

My72Cutlass

Ok Thanks Joe, I allready have the fuel return line that I purchased I just didnt know if I should return it since I didnt need it..... When I had the car runing I do remember some odor of exhaust or fumes, so maybe I should just use it and replace the sending unit with a sending unit with 2 ports!!!!!