Hi Grumpy. I've been trying to think of which one is the main tank. All that I can think to do is to use both tanks until both are almost empty and then fill up both to see which one takes the most fuel when you re-fill. That one is probably the main one. If you figure it out let me know.
The rear tank is the main tank, not all broncos have two tanks and those with one have it in the rear Siggi
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