Fuel line routing

[bigblockchevelleman]

Is there a diagram that shows the lines from the tanks ( 87 dual saddle gas tanks  ) I have completely rebuild the truck including new tanks , sending units,Fuel pumps etc.... truck runs great when on passenger side but when switched to other tank after running a couple of minutes engine stall  and will not start until switched back , then engine runs ruff for a few minutes  , I believe my problem is at the value switch on the frame so I think possible On the tank that causes the problem I may have the hoses routing wrong is there a diagram that shows the lines from the tanks to to the value switch on the frame  ? Thanks for any help Steve

[Mike81K10]

Apparently your passenger side tank is fine. When you switch tanks there is no fuel flow from the divers side tank and the fuel in the lines (that came from the passenger tank) will allow the truck to run a short period of time before it dies out. When you switch back to the passenger tank, it takes a short time to get the fuel flowing and it will run rough until it gets flowing properly. Seems you selector valve is working (could be clogged on the drivers side lines). The lines from the drivers side will be a short run to the selector valve and should be easy to look it over to see if there is a kink. If you want to check your selector valve for clogs you can switch your 3/8" fuel supply lines and see if the problem changes side (switch position - not tanks). Switch lines back when done. You may get some fuel come out the drivers side hose and think it is good. Keep in mind a kink can allow some fuel flow but not enough. This forum has diagrams if you look in the technical area. Could come down to a bad fuel pump/sending unit.

[bigblockchevelleman]

I have checked with a test light plus currently the bed is off the truck pump is running ,believe the problem is at the rubber hoses where they connect to the selector switch on the frame   . What I believe the issue is maybe the pump is actually feeding into the return instead of the carburetor was hoping someone had a diagram that shows the routing of the hoses to the selector switch on the frame Thank you very much for your help Steve

[frotosride]

This should be easy to figure out the routing without a diagram. There are three different size hard lines going from the driver's side tank to the selector valve/switch. The smallest is the vent that feeds fumes up to the charcoal canister, next larger one is the return 5/16 the the largest is the supply 3/8. The selector valve has the appropriate sized barbs on it for each of these. If I find a diagram I'll post it for you.
Worse case I'll take my heat shield off and take a pic, labeling what's what.
Hopefully this helped a little for now.

[bigblockchevelleman]

Thank you very much for your help Steve

[VileZambonie]

See attached

[ColonelSanders]

You could have cracks in your hose causing it to suck air, or an issue in the tank. I’d put a hose on the selector and drop it in a gas can to test it is switching tanks and hooked up right, and work my way to the tank.


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[Customdeluxe81]

I’m with the colonel on this I had a similar problem with my 81 c10 (but single tank) where if it started it ran rough then died off after a few seconds and if I took the line off the carburetor and cranked it and no fuel was coming out of the line ..... so after replacing the fuel pump and it not curing the problem I ran a short line to a small can of fuel and it started and ran fine.... so I found out that the steel line was leaking and it was loosing prime.