Q: Early 2011 MacBook Pro won't start up

Is ti plugged in? Fully charged?

Give us some facts!!!!

Check out this link: If your Mac won't turn on - Apple Support

Kim

If you could give us a few clues that would help.

What is the screen showing?

Are you getting error messages?

Kim

Hi Bummy:

Here is some stuff you can try.

Computer Won’t Start Up:

Then try reseting SMC. Reset the System Management Controller (SMC) on your Mac - Apple Support

Try reseting NVRAM. How to Reset NVRAM on your Mac - Apple SupportThen try a Safe Boot. Try Safe Mode if your Mac doesn't finish starting up

Also check out this help file. If your Mac won't turn on - Apple Support

Also check out this help file. Troubleshooting Startup and Login Items

Also check out this help file. Top 10 Troubleshooting Tips for Mac Startup Problems

Tackling Macs that always boot to Safe Mode. Tackling Macs that always boot to Safe Mode

Startup Screens :  About the screens you see when your Mac starts up

Make a Genius Bar appointment:  Genius Bar

The evaluation will be FREE.

Kim

Here is some additional information for you to try.

White or Blue Screens of Death:

White Screen of Death: Startup chime, no boot, white screen of death

White Screen of Death issue: Get stuck with white screen at Apple logo during El Capitan booting

Startup Screens : About the screens you see when your Mac starts up

Kim

It look like your problem may be the SATA cable or hard drive failure.

MacBook Pro 13" Mid 2012 Hard Drive Cable Symptoms: Symptoms

MacBook Pro hard drive SATA cable issue. MacBook Pro Hard Drive Cable Failure-Free fix and preventative maintenance

To test whether the problem is your hard drive or SATA cable:

You can remove your hard drive from Mac and install in an external enclosure OWC external case or using a USB to SATA adapter USB to SATA adapter and connect it to your MBP via USB. And then try to boot from it using Startup Manager. This will help to identify if your hard drive or SATA cable are at fault. If it boots the MBP, most likely the problem will be the drive SATA cable needs to be replaced.

Boot from the disk using Startup Manager: How to choose a startup disk on your Mac

Kim

1. try booting into what's called "safe" mode. It disables pretty much everything except the core OS - hold shift while booting. If that works it is some conflict in 3rd party add-ons.

2. Kim mentions that it could be a drive or cable. Possible.  Do you have an external drive you can boot to? (everyone should, few do). if so boot to that and then we can do diagnostics on the internal drive.

3. In fact, can you boot to the recovery partition and then do diagnostics on the main partition and drive itself?

Grant

Hi Bummy:

OK, so you replaced your hard drive. Chances are your hard drive is good. It could still be the hard drive SATA cable.

To test whether the problem is your SATA cable:

You can remove your hard drive from Mac and install in an external enclosure OWC external case or using a USB to SATA adapter USB to SATA adapter and connect it to your MBP via USB. And then try to boot from it using Startup Manager. This will help to identify if your hard drive or SATA cable are at fault. If it boots the MBP, most likely the problem will be the drive SATA cable needs to be replaced.

Boot from the disk using Startup Manager: How to choose a startup disk on your Mac

Kim