I am trying to put an TBI from a 1987 K2500 in a 1986 K2500 with dual tanks, I have a donor vehicle but some one has removed the fuel selector valve from it and turned it into a single tank donor. I have the dual tanks on my 86 and from what I can tell the selector valve are the same from 1981-1989 so no problem there but what do I need for a electrical switch to swap the fuel gauges and also switch the fuel tank pumps as I have the in tank ones from a 1987? I also notice in the LMC book that the dash switch is different in the 87 but have that also. I was wondering if the electrical swap took place in a switch mounted under the dash or on the fire wall? Also what do I need for wiring the two tanks together as I said they converted it to a single tank? Does any one also have a wiring diagram for the 1986 and 1987 trucks with dual tanks or where to get one? I have a Chiltons manual and a Hayes manual but neither have a diagram for a dual tank setup.

 

You may have to get an universal tank line switch and also a set of relays. If you wire the switch so that the power lead runs through the switch on the dash then you could just run that power to the switch for the fuel lines and the relay for the pump for the corrisponding tank. So when you flip the switch for the drivers side tank you should have power run to the fuel line switch and the relay for the drivers fuel pump. (Running a relay for the pump will prevent drops in amperage because of the pump and switch running on the same source. I don't know how much power each of them draws, so I would be safe then sorry!)