88' 5.7 TBI /w Saddle tanks 86'

[86K10w88TBI]

Hello, 1st post here, looking for an answer on a fuel issue that I am having with a conversion that I am in the process of doing. I have a 1986 K10 that had a 305 Carb, and I have taken the TBI 5.7 from a 1988 suburban all of the wiring to accompany and put in the 86'. I would like to maintain the stock fuel setup as much as possible (Dual tanks) and have ordered the 1987 K10 TBI in-tank pumps to replace my 86 carb ones, that being said, I am running into an issue with the "tan" power wire for my harness. I would like to maintain that wire but am unsure how GM switched (or if they did) one tank off and switched to the other. Because I was looking and the Tank selector valve from the 86' and the 87' are the same part number from GM. The valve that I have in the truck doesn't accommodate for the "tan" fuel pump power wire, so either GM had a secondary switch that changed which tank was "on" when the selector switch was depressed or they just had them both running all the time. Also the manuals that I have for wiring do not account for anything past "Tan -> Fuel pump", it is like they just didn't care about the dual tank setups.

I am sure I am not the first person to ask this but internet...

Couple of things I have noted cruising these forms:
1) No, I am not going to use a inline pump
2) I know I need baffled tanks
3) I am trying to maintain as much "stockness" as possible
4) I am not getting rid of my "dangerous" fuel tanks, there have been 18 deaths in the history of all these trucks related to the tanks, I will take my chances

 

[MadOgre]

Just use the setup that the 86 already has

 

[foamypirate]

Hello, 1st post here, looking for an answer on a fuel issue that I am having with a conversion that I am in the process of doing. I have a 1986 K10 that had a 305 Carb, and I have taken the TBI 5.7 from a 1988 suburban all of the wiring to accompany and put in the 86'. I would like to maintain the stock fuel setup as much as possible (Dual tanks) and have ordered the 1987 K10 TBI in-tank pumps to replace my 86 carb ones, that being said, I am running into an issue with the "tan" power wire for my harness. I would like to maintain that wire but am unsure how GM switched (or if they did) one tank off and switched to the other. Because I was looking and the Tank selector valve from the 86' and the 87' are the same part number from GM. The valve that I have in the truck doesn't accommodate for the "tan" fuel pump power wire, so either GM had a secondary switch that changed which tank was "on" when the selector switch was depressed or they just had them both running all the time. Also the manuals that I have for wiring do not account for anything past "Tan -> Fuel pump", it is like they just didn't care about the dual tank setups.

I am sure I am not the first person to ask this but internet...

Couple of things I have noted cruising these forms:
1) No, I am not going to use a inline pump
2) I know I need baffled tanks
3) I am trying to maintain as much "stockness" as possible
4) I am not getting rid of my "dangerous" fuel tanks, there have been 18 deaths in the history of all these trucks related to the tanks, I will take my chances

Best bet to keep it all factory GM is to find an 87' pickup with TBI and pull the selector valve and full wiring harness to the dash switch. That's what I did when I converted my 84' to TBI.

 

[86K10w88TBI]

The switch in the dash is different for the 87'? I was looking at another thread and it looked like the wiring diagram looked something like that, but was unsure. Let me look into that more. Thank you for the suggestion!