Coal plants don't import fuel

[airsize]

I have 3 coal plant in my city.
After they ran out of fuel, no import replenished these plants.
I waited for fuel truck about 10 minutes before my city bankrupt and dead.
I am pretty sure I connected outside road, otherwise my city wouldn't grow to 2k people.
So I think it is a bug.

 

[airsize]

After I reload the save, for some weird reason, the coal plants get fuel trucks!
I didn't change any road or something, just reload, and they get trucks.