My 350 2 barrel car has a single line coming into the fuel pump and the one line going out to my little carburator. I think my fuel pump is out and when I called on one they asked if it was a two line or a three line. My fuel gauge has been off for a long while and when pricing a new sending unit it has a single line or a two line. I figured the one line sending unit and the two line fuel pump are what are in my car. What/if any, would be the advantage since I have to replace both of them anyways, to upgrade to the two line sending unit and the three line fuel pump? If I did the return style three line pump would I want to put a inline 5-9 lb electric pump to always help to keep pressure? Is there and difference in the fuel pressure between the two pumps?

Thanks a lot, any info will help!
Ryan

 

There are two kinds of mechanical fuel pumps for Olds motors, with fuel return (three line) and without (two line). The two line pumps have one inlet and one outlet. The three line pumps have one inlet and two outlets, a large one to the carb and a smaller one that returns to the tank. The whole point of the return line was to help keep the fuel cooler by constantly circulating fuel from the tank to the pump. It was mainly used on cars with A/C or high output engines, basically those cars that might be susceptible to fuel percolation. If your car currently has a three line pump, you should replace it with a three line pump. If you have a two line pump, you can use either and just cap off the return line at the pump if you get a three line pump.

 

Well if I were to put a three line pump on it I was going to put a return style sending unit on it also. Its not a high output engine but it does have A/C. So the only advantage to updating to the three line is to keep my fuel cool? I might go ahead and update both of them.
Thanks