Replacing fuel tank issue

[bonfire]

I have an 1986 K10 Silverado with a 350 engine and dual fuel tanks. Both tanks were rusty and leaking so earlier this week, I had a performance shop install a new tank and sending unit on the driver side and the truck was running fine since. Today, I decided to pull off the passenger side tank myself and got it out without to much problem but didn't plan on replacing the tank and sending unit until later this week. The sending unit on both tanks has 3 outlets.

After pulling the passenger side tank off, I plugged the 3 hose outlets under the truck that had run to the old tank's sending unit that run to the fuel system. Prior to pulling the passenger tank off, the driver side tank was selected and working fine. I then started the truck drove it outside and shut it off. About 30 minutes later, I tried starting the truck and it ran for a few seconds and shut off and can't get it started. I am no longer getting any fuel to the carburetor. When I flip the tank selector on the dash, I can hear it click back and forth. When selecting the driver side (down button), the gas gauge shows 3 quarter tank and when I select the passenger switch (top button) it buries the gas gauge way above the full mark so it appears the switch is working fine.

Any suggestions on why I am no longer able to get fuel from the drivers side tank after removing the passenger tank? My hunch is that GM has a "default" tank and when I disconnected the passenger side sending unit which had 3 hose lines, 1 ground wire and some other wire that clipped to the top of the sending unit, that the tank selector is not really switching to the driver side tank even though I can hear it and confirm it by watching the gas gauge change. I have no reason to believe that the fuel line is plugged with any dirt or obstruction since it was working great earlier today.

Thanks for any help!!

 

[HotRodPC]

I do believe your hunch is correct. So what you can do until you do replace the other tank, is get proper lengths of 3/8 and 5/16 fuel line and go direct from your new tank to the steel fuel lines running to the fuel pump. You're by passing the gate selector by doing this, but keep the switch in the correct position so your fuel gauge works. You may have to block off one them on the tank. IIRC, the 3 lines are the feed line, Evap recovery and return.

 

[bonfire]

I do believe your hunch is correct. So what you can do until you do replace the other tank, is get proper lengths of 3/8 and 5/16 fuel line and go direct from your new tank to the steel fuel lines running to the fuel pump. You're by passing the gate selector by doing this, but keep the switch in the correct position so your fuel gauge works. You may have to block off one them on the tank. IIRC, the 3 lines are the feed line, Evap recovery and return.

Thanks for the suggestion. I also thought about reconnecting the old sending unit and connecting it back up (minus the tank) and see if some magic happens.

 

[75gmck25]

For the first few years (up to about '79?) the default tank was the passenger side tank, so if you had a single tank it was on the passenger side. then GM switched to having the default/single tank on the driver's side.

Your truck should default to the driver's side tank f the switchover valve under the truck loses power. Based on your description of what you did, you should be able to run fine with the switch in the driver's side position.

Bruce