I'm rusty on pcs...
My PC is a clone i5 based unit with integrated video and sound. Nic is peripheral. So it blew 2 PSUs over it's 5 years. Last psu is used from another box. It dies.
What I need to do to power on PSU is DC the 12V 4 pin plug on mobo, then still I need to jumper green to ground to turn it on. I tried pulling all cables, still need to jump start and it hates that extra 12v output... If it's out and powered on, PSU dies once it's plugged in, pulling it doesn't resume power, you have to recycle the green wire.
Mobo, CPU, or PSU? THOUGHTS?
... I need to jumper green to ground to turn it on.
The PSU is turned on (in standby mode) once you plug it in. Grounding the green wire switches it from standby to fully on. This is how all modern PC power supplies are designed.
The 4 pin plug supplies extra power to the CPU. If you leave it unplugged, the CPU will close down the system when it senses it hasn't enough power.
Your problem appears to be that the power consumption of your hardware exceeds the rated power output of the PSU. That will shorten the life of the PSU.
Some common causes
Old CPU heat paste Can shut down both the PSU and the computer.
That can slightly be dependant on the paste used as some ages better than others.
Simple thermal tests that most motherboards have could confirm that.
If you add new paste NEVER throw extra on there as it is just meant to aid heat transfer over short uneven distances. Credit card method is best to apply it.
Inefficient fan system.
Always use a PUSH PULL and not a PULL PULL or PUSH PUSH.
Blow out the PSU and CPU heatsinks (and everything else) but do not forget to stop the fan rotating before you do it or you could simply burn out the fan bearings.
Internal hardware badly arranged.
More so hard drives and graphic cards.
Ensure airflow covers as many items as possible. Some cases have more hard drive bays than they will ever need so seperate hard drives by one bay when you can.
If its a mainstream box most were made with the minimum PSU required and it can be well worth an upgrade to the PSU itself.
Most boxes are also capable of extra fans and these can be well worth the investment.
Raise off soft flooring (ALWAYS) as some also depend on low surface air intake.
Also static is slightly more prone to some carpets and can cause issues of thier own especially in winter months
If your has any filters remove and clean at least yearly.
Front panels should also be considered a dust trap.
Some just pop out so it makes for easy cleaning but check first.
Oh and just because you can jump green to ground does not mean the PSU is 100% working.
You need to check the voltages are within tolerance. Quite easy to get a PSU running and then find a low or missing voltage.