GRUB is running but OS not booting, RAM could be defective

Question

My laptop got slightly water damaged and, before I learned it was a really bad idea, I tried turning it on to see if it was working. What happened was the following:

1. I pushed the power button and it lightened.
2. The splash screen of my Dell Inspiron 15 7580 showed up, which, unless I'm mistaken, means the POST (power-on self-test) was performed.
3. Grub appeared and, as always, allowed me to select between my two OS, Ubuntu and Windows 10. I can also press ESC and go to the Grub shell.
4. When I selected any OS, the screen became black and nothing else happened. The computer stayed turned on until I forced a power-off with the button.

My hypotheses

I might be mistaken in any of these points, but I hypothesize that:

• If the computer manages to stay turned on and run code from the UEFI, this must mean that the power supply and the motherboard are OK.
• If I can enter Grub, this means that the boot loader can be accessed from disk, so the hard drive should be OK.
• If things start failing when I choose an OS, then it looks like the OS cannot be loaded into memory, hence my RAM could be damaged because an OS cannot run without RAM (see Does every OS need RAM?). But isn't Grub loaded into memory also?

My questions

• Can Grub be run without a functioning RAM? Is there any other memory or cache that the computer could be using to load the bootloader? I suppose it is a really small program in comparison with an operating system, so maybe the UEFI could fit it somewhere else.
• Is there any other reason that seems possible for a failure booting up the OS, considering the setup I described?
• Can you get any clue of what piece of my laptop could be failing, based on the fact that Grub runs but not any OS?

Current state of my laptop

After learning that you should never turn on the laptop after water damage, I haven't started it again. Turned off and unplugged, I opened it, found a few small water drops around the battery and the memory, which I immediately dryed. I will wait for a couple of days before turning it on again, in an attempt to make sure that all water goes out with some help of gravity.

For this reason, I don't know yet what's the state of my laptop right now, after it was dryed.

Answer 1

There is a good chance that your OS is corrupt (could have been a crash, bad update, bad shutdown) or it could be faulty hardware. Your first troubleshooting step is reinstall Linux (which is to also reinstall GRUB, which could be the issue).

If that fails, format the hard drive and install your OS(s) again. You may just need a fresh start.

From what you posted, power supply, graphics, and CPU can be ruled out as hardware issues. The motherboard, however, can't. It could be a faulty port.

Hardware wise, here is a couple troubleshooting steps: First,if you can, open up your computer, and check that all of your cables in there are firmly connected, along with any hardware connection (ex, CPU sitting on motherboard, RAM all the way in slot(s)). Next, unplug your machine and hold down the power button for at least 30 second. That will ensure everything is fully off.

If all of that fails, I'm afraid we will need more details to troubleshoot. I'd advise running hardware tests (through BIOS/UEFI menu or off of USB/disk), and update your question with them (and I'll update my answer when you provide more info)

Just a side note, though: if your PC got wet, turning it on before a couple days was a very bad idea. You may have caused more damage