fuel selector switch

[ken0275]

Hello,

I just installed a new aux. fuel tank and new sending unit in my 76 Bronco.

I need the wiring diagram for the dash mounted fuel gauge selector switch. The factory plug was removed and it appears to only have 2 wires with crimp connectors going to the switch. OF COURSE I had to unplug both wires and now both gauges read empty. Since switch is still in the dash I am not sure where the 2 wires go.....I am such a boob

Any help would be appreciated

 

[Rons beast]

I don't have a diagram for a 78, but my haynes manual shows pnk/blk or red/wht into the switch, and out to the pumps are 1 red wire and 1 brn/wht.

Hope this helps.

 

[ken0275]

I found a third wire with a crimp connect on it. I assume it really only needs 3 wires to operate the gauge. I just need to know where to reattach the wires.

I have 2 orange very thin gauge wires and another color, which I cannot remember for the life of me right now.

 

[Rons beast]

A guess would be to check to see which wire has power with the key in the run position. I would then use a jumper wire with a 10 amp fuse to temp connect to one of the orange wires. This would complete a circuit just as the switch would. With luck this will energize the gauge, sender, and fuel pump. Then try to jump power to the other non powered wire.

That will complete the circuit to the other tank/pump, sender and gauge.

If this works, you will have to attach the wires and try each combo to the switch. Again a guess would be to attach the powered wire toany lug that is appart from the others.

Good Luck and let us know how you did.

 

[Bully Bob]

I'm not seeing what this has to do with fuel pump(s)

That switch, as far as I know, changes the signal fr. the rear to the aux. tank...up to the gage.

If you look in the parts cat. there's 4 plug/blades on the switch.

Beyond that, it's by me... older (mine) rigs didn't come with dual tanks.

I've hooked up a few way back when.... :-" as Ron says..., testing & using a volt/ohm meter.

 

[Rons beast]

Could be my bad....the diagram I'm looking at showed the wiring going from the tank selector switch to the fuel pumps and senders, but I didn't have one for a 78.

I am guessing here a little.

 

[Bully Bob]

No biggie.., (I think you mean'76)

On one EB., I forgot that switch changed the tank sender signal only. threw the switch & soon ran out of gas...gage reading 1/2 full. :blink: (Didn't move the valve below the seat to the tank with gas)

NOTE: there is a schematic for wiring an "electric" tank switch-over valve to this same dash switch.... allowing you to do What I couldn't. (above)

i.e. one switch changes tanks & gage reading.

 

[ken0275]

My bronco has the manual switch just below the drivers seat to switch from one tank to the other. The switch on the dash shows how much fuel is in each tank.

 

[Bully Bob]

YEP...! All dual tank EB's came fr. the factory with that same set-up.

My point was., folks can eliminate the valve under the seat by using an electric valve, & wire it to the dash switch. Thereby, changing tank feed & gage reading with one throw of one switch, if they chose to do so. >-

 

[Bronc76]

Ken,

My '76 also has two tanks, if you like, I could post a pic of the wiring on the selector switch if this helps you.

 

[ken0275]

Jeffs Bronco Graveyard had this schematic for a 74 Bronco

http://broncograveyard.com/dia/6/wirschem1_16.jpg

I am by no means an electrician, but I just can't see how it would work.

 

[Bully Bob]

BTW., we're assuming your rig had two tanks fr. the start.

There should be two wires (one fr. ea. tank) leading into the switch.

There should be one wire "out" from the switch up to the gage.

Ya that schematic is a bit technical.... however you can see the tanks/switch in lower right. (Two in., One out) (This switch is reading the left tank)

Bronc76's pics would likely help you.

 

[ken0275]

Welp, After a few trial and errors I think I figured it.......BUT!!!!!

I am almost positive my manual selector switch is not working. One gauge reads almost full. Which would be about right since I only put 6 gallons in the new Aux. tank.

The main tank shows about half. It was almost full when I started this project and I drove the obsession a few times.

When I move the tank manual selector switch to the off position truck does not shut off at all. So I will now have to replace that.

So.....J.B.G. is going to take more of my money again.

Thanks for all the help.

 

[Bully Bob]

Good job...!!

BUT.,

"When I move the tank manual selector switch to the off position truck does not shut off at all."

I don't think this is possible..

First, it takes quite a while to burn the fuel in the lines.

Second, I believe those valves are all metal...probably a "ball valve" in there..! (& maybe a 'lil seal or two)

I could imagine one getting plugged.., but not continuing to flo when off.

However., easy to remove & test by mouth or air pressure.

 

[ken0275]

Welp.... I ran it about 20 minutes over the weekend in the off position and it kept running.

After ordering a new valve, I decided to try one more time.

I started the truck, moved the switch to off and almost 3 minutes later the truck died. I repeated it and samething happened.

It still apppears to be sucking on the main tank only not the new Aux. tank.

I have had this bronco for almost 4yrs and from day one I discovered the Aux. tank had a bad leak and I never used it.

I do not know how long the previous owner drove on the main tank only...

I ordered a new valve and when it comes, hopefully that will fix the problem.

I did check all the gas lines and the previous owner replaced them all except for one.

Which I need to do when the Aux. tank is empty.

The rubber hose at the new sending unit drips a little. I sliced it when I was removing the old tank and forgot to replace it.

With any luck the new tank starts working I will be able to change that hose.

 

[Bully Bob]

"The rubber hose at the new sending unit drips a little."

This will allow the pump to pull air into the line...prob. more so than fuel.

Could be why it only runs on main tank.

 

[ken0275]

My drip stopped. The manual selector switch maybe working, but I am not sure.

I ran the truck for 4 yrs on the main tank, so I never used the selector switch. So I cannot remember which way it was pointing.

There is a new placard at the switch which reads Aux, Off and Main.

I see that the handle on the switch is held on by a ****** can that be reversed?

How do I know which tank is being used?

Does the little hand point to which tank is being used?

OR

Does the big hand cover which tank is being used?

I am such boob!!

I should take pics before I start a project

 

[ken0275]

"The rubber hose at the new sending unit drips a little."

This will allow the pump to pull air into the line...prob. more so than fuel.

Could be why it only runs on main tank.

That little drip was coming from the only rubber line I did not replace. I slit it with a razor blade in order to remove it from the old sending unit and I forgot when I put it back together. I believe I need to get the tank empty before removing that line or else I will have 6 gallons of gas all over my garage

 

[Bronc76]

The big side of handle points to the name of tank:



The handle could be reversed I suppose. To be sure, you can also trace the hoses from the lever to each tank but I think you have to drop the aux. tank to see them.