4.5 HP Briggs & Stratton Engine keeps dying out

Older mower but used to run great for 15+ years. Changed carborator diaphragm last year and ran great. This year it would start then cut out within 10 seconds. Once warm it ran well for the first month. Then Started dying and would not stay running. Changed diaphragm and it did not work. Starts well and can run for 10-15 seconds at most or any load and it dies. Sounds like it isn't getting enough gas. Changed spark plug and emptied fuel. Still no change. Changed diaphragm a second time in case it had a pin hole.

I don't have a compression tester. Any other idea. The spark plug connector had some tarnish but it runs smoothly for 10-15. Any help would be great. Have to DIY this :)