I just got my very first car, a 1973 F-250 camper special custom. It has 2 gas tanks and one of them doesn't have a key. The other one has a key but doesn't lock (it fell out on my way to school once - that was fun) and I am going to order 2 new caps from LMC or Kragen. The only problem is that I'm not sure how to tell if they have evaporative emissions control or not. How can I figure that out?

 

Look on the passenger side frame rail and look for Line 2 here Truck Parts and Truck Accessories. If you have it, you need non-vented gas caps. If you don't, then you need vented gas caps. You will need vented gas caps if a PO removed those lines and blocked off the vents.

 

Alright thanks a lot. It turns out they're non-vented. I got 2 new caps with keys and now I don't have to worry about my caps falling off on the road!