I have two gas caps and dont know which one is the main line

[aveti]

So i bought my 74 bronco in the past year and its been in the shop for most of the time ive had it. Its a dual tank and im just wondering which gas cap leads to which tank? Is the gas cap closer to the driver door the aux and the gas cap closer to the rear bumper the main?

 

[phyler]

So i bought my 74 bronco in the past year and its been in the shop for most of the time ive had it. Its a dual tank and im just wondering which gas cap leads to which tank? Is the gas cap closer to the driver door the aux and the gas cap closer to the rear bumper the main?

Yes, aux is closer to the front.

Sent from my Pixel 8 Pro using Tapatalk

 

[gnsteam]

Thought I would add some information about using the tanks. There are two switches that control the use of the tanks. There is a switch located on the far left side of the dash. This switch selects the sending unit of the tank selected and displays the fuel level of that tank on the fuel guage. The second switch is located on floor below in front of the driver's seat. This valve (switch) selects which tank is supplying fuel to the engine.

 

[Tiko433]

Good info gnsteam…I remember when I first got my 69, one day it just died on me … of course I checked and thought of everything other then me using both tanks and I ran one dry. The valve has a handle on it . I thought the handle pointed to the tank it was selected for. However if you look closely at it the pointer is opposite of the handle. Maybe Im the only one how has done that but you have to put your head down there and look. Not something you can see while driving down the road. There should be a plate that says AUX -off- Main

 

[Scoop]

I remember the proper switch/valve setting is the valve handle and the switch toggle will point in the same direction - towards driver side for main and towards passenger side for aux tank.

 

[Blitzen72]

Wild Horses has an improvement on the original valve under the driver's side knees... an electric valve that ties into the dpdt switch on the dash - a simple flick of the dash switch changes both the signal from the sending unit AND flips the valve to the 'other' tank.

I haven't looked... the other bronco vendors probably have the same unit as well.

I put mine in when I replaced all of the fuel lines. A "3 beer" job at most. Now that valve lever is under my knee for looks only.

 

[Nothing Special]

I've had a couple of the electric valves (don't remember were I got them). The first one stranded me on the highway with gas in one tank but it wouldn't switch off the empty tank. The replacement failed in a different way. No matter which position it was in it would draw from both tanks. I don't know if it constantly drew from both or if it switched back and forth on its own. But it resulted in my not having the full tank I thought I'd have when I ran the other tank low.

I love the operation of the electric valves, where you don't have to reach down where you can't see to switch a valve and also flip a switch on the dash to get the gauge to read correctly. But I like the dead-simple reliability of the manual valve more, so I went back to the stock setup.

 

[gnpenning]

The GM valves will default to the passenger side when they fail. Depending on which tank you want to use as your main tank that is something to keep in mind.

For me I want the main as my default tank.

 

[OX1]

I liked the dual tanks and didn't want the larger road grader rear tank setup. I use a transfer pump on side tank, so
the main tank can use an EFI pump and return, but it does not have to be duplicated on side tank.

I still use stock guage senders and switch on dash. Switch on dash, when set to side tank, also turns on transfer pump.
I only need it set to that side long enough to empty that tank into main.

 

[Broncobowsher]

The rear tank was standard and every Bronco got one. That is the main tank.
The forward one under the drivers seat was an option. Only got that if the option box was checked. That is the auxiliary tank.