I've recently bought a 74 GMC K15 with dual tanks and the left tank was disconnected and is not being used, the previous owner had replumbed it to bypass the left tank and looking for a diagram on how it's supposed to go. Any leads would be appreciated. Jake
Jake ; Right about the time your rig was made , GM went to multiple hoses on the dual tanks ~ one will be the fuel nipple , the other is for the vent and needs to be connected both to the other tank and to the underhood charcoal cannister or vented to atmosphere with some screen over the open hose to prevent those pesky mud dauber wasps from building a nest in it and causing you weird running problems . The switch over valves were electric and dead simple , they also switch over the fuel gauge when you switch tanks . Plenty of dual tank valves to be found in junk yards or you can use a manual brass valve . Remember to test the unused tank to weeps & seeps _before_ spending time & $ hooking up the hoses and valves etc.
