Hello.
If you want the tank to stay put, you could make him start without fuel.
then you can use setfuel 1 on him when he needs to move and it will go
also when you want someone or some vehicle to hold at a certain waypoint, by using a trigger on it to make em go, you should not use that trigger on the waypoint they have to go to, but have a waypoint before that close to the unit.
the unit will wait at this one, till trigger is activated and then go to the next.