FIXED: Samsung Galaxy S4 wont turn on (Troubleshoot and solution)
Why Android Enthusiasts Stack Exchange recommends it
Android Stack Exchange answerers point people to it when an S4 will not power on or shuts off after a couple of seconds, since it shows how to test and replace a stuck or faulty power button.
Recommended by 3 people across 3 different months, 2015 to 2015.
What it is
A 20-minute repair walkthrough by an individual creator showing how he revived a Samsung Galaxy S4 that would not turn on or charge. He disassembles the phone, uses a voltmeter to trace the fault to a faulty power button component, replaces the roughly $5 part, verifies the fix and reassembles the phone.
What people said
Recommends user104192 · 2015-04 · Android Enthusiasts Stack Exchange · on “Samsung Galaxy S4 will not boot, turns off after 2 seconds”
I think this might be the power button that got stuck and need replacement. Here's the link for troubleshooting and solutions. You might need some simple electrical skills. [this video]
Recommends user114429 · 2015-06 · Android Enthusiasts Stack Exchange · on “S4 Wont turn on unless removing battery then turns off after 2 seconds”
I had the same problem. Most likely it's the power button problem, where it's always stucked inside, or depressed in. That makes your phone turns on then turns off by itself. I had the same problem. I found this great video on how to fixes it. [this video]
Recommends CKKho · 2015-07 · Android Enthusiasts Stack Exchange · on “My samsung galaxy s4 won't turn on”
I think most of not starting up and flashing are related to the faulty power button. Here's the link you can follow on how to troubleshoot the power button if it's working properly or not using a voltmeter. [this video]