Bought an old Coleman 425D 2 burner stove at a yard sale a couple of years ago but never even looked at it till I started on my camper. Cleaned it up enough to see if it worked and sure enough it didn't. Did a few of the basic clean all tubes and valves and make sure all fittings were tight kind of things and when it still wouldn't hold pressure for more than 3 minutes, did a search for info.
Found this site:
http://www.oldtownyucca.com/coleman/ which quickly showed me the things to check. Turned out to be the first thing I had checked

which was the seal on the tank fill opening. Was cracked and wouldn't hold the amount of pressure that was needed for a good flame. Bit of cutting and scraping to remove the old seal and a trip to the plumbing repair parts box for an o-ring to replace it with and it fired right up.
Now to get off the computer and go finish the camper so I can go camping and use the stove...
