Here is my reply to another post on this same topic:
The best way to fix the problem is remove the latch assembly and thoroughly clean it to remove all the grease and grime. Once clean, you can locate the offending broken spring. Mount the latch in a vise where you can have good access to make the repair. You will see that the spring is held in place by 2 short tabs that are bent at a 90 degree angle to the latch and pinched together to hold the spring. Use a propane torch with a narrow pinpoint flame and heat the 2 tabs until they are almost red. While still hot, you can then bend them SLIGHTLY; just enough to remove the spring without damaging the tabs. (Be careful with the tabs - you'll need to use them again). Install the new spring in the latch mechanism making sure it's nestled in the right spot and heat the 2 tabs again then take a pair of pliers and pinch them back together to firmly hold the spring in place. After things cool down, use your favorite spray lubricant on all the moving parts and you should be ready to reinstall. I would test it by inserting the handle and make sure it returns to suit you. You can do it!
