Dual fuel tank switching schematic

[TexasJeff]

Does anyone have a schematic of the dual fuel tank switching circuit they could share with me. I have the schematic for the basic chassis electrical but it does not show the dual fuel tank switching circuit.
Need to be the non injector, non electric fuel pump schematic. I have searched the site and only found ones for injector and electric fuel pump version.

Thanks in advance,
Jeff

[hatzie]

All of the GM factory schematics are in my signature.

Some of the 1980 trucks had an additional timer relay that is not in my schematics...http://67-72chevytrucks.com/vboard/s...4&postcount=36

[TexasJeff]

Thanks Hatzie you are the man, mine is an 80 and with the extra timer relay..

[hatzie]

That timer relay is obsoleted by GM.
They are keeping the aux tank selected when the ignition switch is in the Start position.

You could accomplish the same by building a retained accessory power circuit using a 3 ISO relay pack.
http://www.the12volt.com/relays/relaydiagram30.html
Fused 12v+ would be to a battery connection that's hot regardless of ignition switch position (acc, off, run, start).

[TexasJeff]

Hatzie I did find the relay at a few places on the web, 2 on ebay (one for $43.95 and $39.95) and another on some obsolete GM parts website for ($60). I bought the one for $43.95 the guy offered free one day shipping.

And thanks for all your help on this matter, I will save that schematic of the relay set up for future use.

[dannyboy]

My 72 K20 had two saddle tanks installed in 1972, but they didn't have 90ohm sending units at all. So I purchased 2 off ebay and installed them, purchased a dual tank selector switch BDW S9020. Ran new wires from saddle tanks to switch where I installed it by drivers door dash. I had a manual valve so no solenoid valve, darn it, maybe someday. I kept the original fuel gauge and just switched its reading point. I plan on removing the cab tank and selling it or giving it away. The fuse block fuel tank terminal has a automatic connection to the fuel gauge so nothing was needed to do there.
But in order to keep up with changes, if I ever sell this K20, very unlikely, I made up this schematic.
Was a very easy thing to do!
Hope it helps one person doing this same thing.
A 3way switch would of been needed if I were to keep cab tank.

[Nessmuk]

Does your truck have a fuel return line?
If not, it's easy peasy with a double pole, double throw switch.
Get a switch without the center off position.
Wire your OEM tank sending wires so that the wire to the dash is in the center position in one side of the switch.
Have your two wires from the tanks going to the same side of the switch, one to the top, one to bottom.
Run a 14ga hot wire to the other side's center terminal.
Run a wire from the top or bottom terminal, so that it is next to the second tanks sender wire. Run that wire to your valve.
Done.
A fused hot wire source of at least 2 amps. The 3 port valves draw 1 amp.

[dannyboy]

You do understand that I am 100% good and working with what I did and how it works. What I find, in doing research is folks want to turn a simple act into a complicated act with words.
WHY
Thanks anyway what I did works and is simple!

[kwmech]

I'm using this diagram and parts on my flat bed with an aux tank. Just eliminate the wires to the fuel pump, not using the module either. Solenoid powers both ways and switches the tank sender at the same time

[Nessmuk]

What's hard about a soft switch and a wire to the tank valve, and a wire from each sending unit to your gauge wire?
Hard is my setup with 3 filters, 2 valves, 3 pumps, two fuel heaters, two water in fuel sensors, and 3 fuel gauges, one for the water methanol tank. All pumps and heaters relay controlled to only work when I'm using that tank.

[El Dorado Jim]

http://products.pollakaftermarket.co...elector-valves http://eaccess.smpcorp.com/eCatalogs...8050-726-1.pdf http://products.pollakaftermarket.co...S_41-revdd.pdf this is good info on installing the 81-85 I think, motorized valves ,they sell these at autozone....

[Nessmuk]

I tried one the motorized valves. Talk about overpriced tinfoil and plastic. Those wind up toys that used to come in boxes of cereal when I was a kid were built better.