adapting two tank setup in single tank truck.

[Muddin_Maniac89]

i am working with a 1986 Chevy K20. factory single tank setup but since im running 40's id like to have 20 more gallons on board. how do i make it a true dual tank setup and not just extra capacity. really trying to get this done before i get my bed back from body shop.

[cjlinkster]

IMHO I wouldn't do it; it seems that a lot of people have issues with their dual tank setups (including my truck).

If you want to do the conversion, you will need:

2 tanks, 2 sending units, diverter valve, and diverter valve switch. Also will need new metal gas lines.

If you could locate a junk yard truck, you could pull the necessary wiring from it. Otherwise you will need to make a custom wiring harness for the switch, valve, and sending units. I would not use the metal lines or tanks from a junk yard truck; these parts are available new for not too much $$.

I am surprised that your k20 didn't come with dual tanks from the factory.

[Muddin_Maniac89]

what kind of problems are there? also i already have two new tanks with sending units. and i grabbed a wsitch from a junkyard truck a while back but have no idea how to wire it up. could only get a few inches of wiring off it since they were closing right when i found the truck. i just wanna know if i go on LMCTruck.com and order a 6 port selector valve and 6 pin connector if i can just figure it out from there. also hows your setup done in your truck? like which color wire goes where and all that?

[cjlinkster]

The most common problems seem to be that the switch stops working or the selector valve doesn't work completely. I have noticed on my truck; that if the switch doesn't work (my switch is set for the drivers side) then the passenger side tank is used by default. Another member posted the same issue with his truck.

If those two parts are good usable units, then what you need now is just a wiring diagram. Just search on this forum for a diagram for the selector valve.

[Muddin_Maniac89]

i may have found one that someone posted a while back but its for an 83. only problem is that the wires coming off the switch in his diagram are not color matching to the wires on my switch so im unsure if itll work the same.

[cjlinkster]

I bet that it would work the same.

It seems to be a very basic type of switch, double throw double pole. A voltmeter may come in handy...

[Muddin_Maniac89]

well i did try a little experiment with my switch and two trailer lights acting as the LH and RH tanks and wired it up same as in his diagram and i only needed 3 wires hooked up for it to seem to work right which confused the hell out of me. so idk.

[notyo_cheez]

Opposite here, have OEM dual tanks and want to go to one. Prefer the driver's side to keep as my daily driver has it there. Tips?

[Muddin_Maniac89]

I can only offer one good tip......sell me your selector valve, switch and wiring. haha.
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[Desert1957]

here is a link to a previous thread , the electric fuel pumps are for an 87 but check the selector valve color code listed and see if it matches your plug

http://67-72chevytrucks.com/vboard/s...11#post3941411

[Tucson38]

Originally Posted by cjlinkster

The most common problems seem to be that the switch stops working or the selector valve doesn't work completely. I have noticed on my truck; that if the switch doesn't work (my switch is set for the drivers side) then the passenger side tank is used by default. Another member posted the same issue with his truck.

If those two parts are good usable units, then what you need now is just a wiring diagram. Just search on this forum for a diagram for the selector valve.

I've been dealing with this for years. I'm never confident the switch or valve is going to work when I want it to.

[notyo_cheez]

Originally Posted by Muddin_Maniac89

I can only offer one good tip......sell me your selector valve, switch and wiring. haha.
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It's a deal, when I've arrived at that point they are yours.

[Muddin_Maniac89]

Originally Posted by notyo_cheez

It's a deal, when I've arrived at that point they are yours.

what year truck are you working with?
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[notyo_cheez]

An '81 Scottsdale stepside.

A local radiator shop said a new tank is cheaper than trying to restore an old one. To save myself some grief I'm just going to install one new and scrap the old ones so I won't need the selector valve.

Anyone know who sells the replacement poly fuel tanks besides JCWhitney? Read a couple of reviews that said they weren't that good quality plus I'm looking for one that's less than $175.

[Muddin_Maniac89]

do your sending units have 2 lines or 3 coming out of them?
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[notyo_cheez]

Looks like two, inbound side of fuel pump has a pressure line and return.