Raspberry Pi doesn't boot after electrical outage

[guidof]

Raspberry Pi doesn't boot if electrical power is connected to the raspberry and to the external USB disk at the same time. Need to switch on USB external hard disk before, and the Rspberry after a while.
If an intermittant power outage occour, Raspberry remain not working

[pepedog]

Is rootwait in cmdline.txt? It should wait forever for drive to become available.

[guidof]

Yes, there is:

[root@blek ~]# cat /boot/cmdline.txt
sdhci-bcm2708.enable_llm=1 sdhci-bcm2708.sync_after_dma=0 smsc95xx.turbo_mode=N dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 loglevel=2 root=/dev/mmcblk0p2 init=/bin/systemd rootfstype=ext4 rootwait
[root@blek ~]#

[pepedog]

You are going to have to e2fsck that second partition somehow.
And remove init=/bin/systemd

[guidof]

The problem is not the SD card (at least I think so), the problem is the external USB hard disk.
Withou external disk Raspberry starts fine. With an external USB hard disk she doesn't.
It looks like the external USB disk must be powered on before raspberry.
After a power outage, USB disk and Raspberry starts togheter but somehow the kernel detects the USB device connected but not yet ready and fails to start.