When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Yes it could be the rings but it could also be due to it not being run in 15 years. If you checked the compression before running it then I'd run it through at least one warm up then check again.
Or squirt something like Gumout into that cylinder, let it sit a while and run it a little to see if compression improves. Then change the oil, now that it's been diluted with Gumout, and you probably should anyway after sitting for 15 year.
Well, I finally got the truck running for a while. I checked the compression in the one low cylinder, and it came up to match the others. Thanks for the help.