[Quote franje] Can i attach the plug+wire directly to the coil outlet? So the distributor does not take part? [Quote]

Yes, that's the best way top check.
If you don't have any help, you can use a jumper wire with alligator clips on the end.
Clip one alligator directly to the spark plug end (where it screws into the engine) and the other to the negative (-) battery post.
This way you can lay the spark plug in a place that you can see when you crank the engine over.
Also check the coil wire for continuity...they go bad too.

Also, as no one has mentioned it yet, you car does have a EZK ignition module. It is located under the driver's knee bolster below the steering wheel.
You will need a torx screw driver (I forget the size) to remove the panel.
It is a black (or silver) plastic box about 5" square with a electrical connector attached
The way to check this is simply replace it with a (known) good module.
You can get a good used one on E-bay for less than $100.

I keep a spare that I bought just for troubleshooting, along with a spare Air Mass meter, Fuel pump relay, RSR relay, Ignition Amplifier, Jetronic II module and Crank Position Sensor.

These ignition problems can make you pull your hair out sometimes, and I find that having good replacement parts can be a huge help in locating them.
They call it "plug and play" at the dealerships but I'm in these Volvo's for the long haul and I'll (maybe) need them eventually anyway.
Why not have them now and use them for troubleshooting?

Hope this helps
steve