How can I find out where my application is timing out?

I'm making a rest webservice call to a system. I can run the rest call outside of my application and get a response in about 2 mins directly to the browser. However, when I make the call in my application it times out too fast. I can get some data back, but any request that takes more than 30 seconds fails.

I think the issue is a timeout. My site/application uses Liberty for the webserver and Ruby on Rails. I don't have a timeout set in the Javascript, so it has to be in the webserver or the framework.

It's a pretty big application. What is a good way to find where the code is timing out?