Or, get a pump with a long hose and pump it out. Let it air out, too. Don't use the infamous "lit match" method, however! 1 or 2 percent "petrol" in a refilled tank of diesel won't kill the motor. Just make sure you pump as much out as possible. Tapping the tank from underneath as you are draining will help you determine (along with the fuel gauge and low fuel light) if you're getting to near empty.
Your problem isn't just the tank, however. Your fuel pump, your fuel lines and your fuel rail probably have gas in them. Can you get to the fuel pump on a Volvo diesel? Don't know since they haven't been sold here in years. If you can, drain it and run diesel through it. (A 12 V battery should power it up.)
The fuel lines from pump to rail might need some air assistance. When both ends are undone, low pressure air should blow them out. Gravity should do most of the work, but they won't be any drainage unless you open the end at the fuel rail/distributor, too. BTW, if there is a fuel filter or filters, replace them if possible as they are mini resorvoirs.
I've never seen a modern Volvo fuel real and injectors, so I can't help you there. Removable without dissembling the intake and/or engine? Can they be "opened" to drain out the gas? Don't know. Sorry.
In the cold north where I live, diesel operators occasionally put a little gas (a small amount) into the diesel tank to keep it more fluid in cold weather. So a 1 or 2 percent mix won't blow up your engine. But you don't want pure gas entering the combustion chamber and exploding/burning out of sync with the engine's operation. That high compression is more than the engine can stand.
Last edited by malaka; 10-06-2010 at 04:09 PM.
Reason: more information was needed.