MacBook stays on grey startup screen with no apple logo

Hello your problem is a falling GPU , remove the logic board and wrap in aluminium foil put your oven to 350 f when is ready set your Logic board inside keep for 8 min NO MORE after the 8 min turn off the oven and wait 30 min to cooling down DON'T TOUCH OR MOVE WHEN IS HOT put all together use thermal paste good cuality and Install after boot the SMC Fan controller put max speed and keep this setup all the time I hope works for you!!

On my Macbook Pro 2009 this is the cable, depending on your macbook it could be smaller. If you click adams disconnecting cable link he has a photo of his. Oddly this did fix my issue as well.

Fixing a Mavericks Installation Problem

How to manage a failed OS X Mavericks installation | MacFixIt - CNET Reviews.

1. Intel-based Macs: Resetting the System Management Controller (SMC).

2. Repair the Hard Drive and Permissions - Lion/Mountain Lion/Mavericks

Boot to the Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Repair

When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu. Select Restart from the Apple menu.

3. Re-download and reinstall Mavericks.

Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.

When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the main menu.

Reinstall Lion/Mountain Lion/Mavericks: Select Reinstall Lion/Mountain Lion/Mavericks and click on the Continue button.

Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.

Kappy,

Please re-read what the OP wrote. I'm having the exact same problems, but the hard drive is empty and I cannot even boot to my disc. I followed this guide from a different thread, Mac OS X: Gray screen appears during startup - Apple Support, and still nothing works.I replaced the logic board with a refurbished one that was certified to work. Although I'm not counting out that the refurb could be the problem, I'm highly doubting that it is. I'm able to eject the Disc I tried to boot to, reset the NVRAM, and also got an error when I pulled the memory out, so the logic board seems to be working fine. What else could be causing this? I've tried other memory, and it doesn't make sense that the hard drive could be causing this. Need suggestions please. Thanks!

I am having the same issue. My macbook pro late 2008 model fell off of my bed and usually I have no issues like this and it is fine. However this time when I opened the screen nothing was broken but I just had the spinning beachball on the screen and it was making all usual sounds. I restarted it thinking that it might just need the restart but it made the normal apple chime and all the normal sounds of starting up but will not go any farther than the gray screen and will not respond to any key responses of safe startup trying to get any screens to appear to fix any issues. I have tried all of the articles from apple and I can not get any technical help without paying $30. If I could get some help on this issue it would be wonderful. I have a feeling that it may be that the hard drive came up taped but I can not get any symbols of that happening like the flashing folder with a question mark.

I thought I'd post this here incase it helps anyone. I had the same problem. No responsiveness to any key I held down when booting, just a grey screen with no apple logo. (On a mid 2010 macbook pro 15".)

From playing around inside I figured out that after disconnecting the camera cable from the logic board the computer booted up as normal. Previously I also had problems with pink lines on white areas of the display and green lines on black areas of the display. So far this also seems fixed.

Are you sure about this ? I have the same issue

Disconnecting the camera cable also worked for me. Cheers to you, adamgx!

Can you send me a picture of what does a camera cable look like? Yes im stupid, im new in mac and having the problem of whitescreen no apple logo keyboard not work