how do i go about fixing my fuel gauge in my 1986 ford f150

To be aware of what air pressure you are inflating it to after the repair.

no not enough mechanical fixing on a 15 gauge nail

Nitrogen-fixing bacteria

I don't think I does but I have had a low oil pressure reading on the idiot gauge as well(as do many). What I found is that its most likely the system the gauge uses, not your pressure. The easy way to find out is to buy a mechanical gauge and see how it reads. Or, this link is great for fixing it yourself.

http://www.rowand.net/shop/tech/FordOilPressureGaugeFix.htm

Good luck