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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: redbull7940 on March 06, 2013, 12:07:55 pm
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Noticed today that I have a fuel leak coming out of the right tank. I don't use the right tank because it has a hole in it. I keep the selector on the left tank. Everything in the left tank is running to the right. Don't have a clue as to why. Does this model have cross over lines that run on top of the tanks? Any help would be greatly appreciated
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The left and right tanks are isolated from each other from the factory, there is no way to get fuel from the left to the right in a factory setup.
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Welcome to the site.
I agree with Captkaos 100%, regarding the factory fuel system.
But, if someone along the way has innocently altered the fuel plumbing...
If the engine mounted fuel pump has 3 distinct fuel line connections, the 'extra' 1/4" line returns fuel to the tank(s) to help control vapor locking on hot days. If the 1/4" return line doesn't switch between tanks through the tank selector, it will return fuel to only one of the tanks; if that happens to be the tank from which you are not drawing fuel, it will effectively transfer small quantities of fuel to the 'unused' tank. Whether this is a possibility hinges on whether you have the 3-port fuel pump without a matched 6-port selector (3 ports for fuel supply, 3 ports for fuel return).
A rare situation might occur if someone blocked off the tank vent connecting to the vapor canister on the canister side of the "tee" inserted between the two tanks. In this scenario when the main tank is completely full, fuel expanding in the tank as it warms might "percolate" into the opposite tank; but it wouldn't be much; and the symptoms would occur only when the main tank was completely full after 'topping off.'
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I have had this happen before also and it ended up being a bad selector switch. It was leaking inside the selector and sending fuel back randomly to both tanks.
Good luck!