I don't find any torque specs for the copper washer connections in the Volvo green manuals. I suspect specs for copper washers are unique to the washers not the applications. Here is a similar question on https://www.benzworld.org/threads/crush-washers-how-much-to-crush.3072989/. They show a torque chart for different diameter copper washers in Nm.

For the B230 fuel filter, the Volvo 700/900 Pocket Data Booklet reference has the torque spec as 15-26 ft-lbs for the Bosch filter, same one used in your 240. 15 is not a lot, so I'd lean closer to 24.

My preference is to do it be feel. It's all about the copper crush washers. My tendency would be to just firmly hand tighten them using a 3/8" ratchet against a combo wrench used as a counterhold then with extra effort try to get an extra 1/16 or so turn to get a crush. As a final check once the system is pressurized I'd probably do a quick wrap of a dry paper towel around the banjo fitting just to be sure.

For more experienced hands, the proper way to do it is by feeling the crush happening and taking it until the crush feels like it's done. After the bolt makes contact with the washer, one should gently turn the bolt, feeling the crush of the washer happening until that magic point where resistance suddenly changes.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi,

I don’t think there is a torque specification for that aluminum housing of the fuel filter.

I know it has to get very tight to crush copper that is technically harder than the aluminum.
That washer appears to get buried into the aluminum more than just a very tight contact of malleable molecules.
As I remember it’s was all I could do to hold down the filter to keep it from twisting the body.

I got it as tight as I could manually and it still leaked a drop.
I ended up just zapping it lightly even more with my air impact wrench.

I put marks on the flats of the banjo bolts, over the fittings plus onto the body of the filter.
This way I could tell what movement I had made with any upward increase in air pressure.
An electric torque wrench would have to have a slipping clutch mechanism or a very astute finger response but I’m sure it’s been done by a few of us!

If you are under a car, that’s against the ground, it might be the only way to insure enough twist and then test it.
Pulling long wrenches with the filter held within its band clamp is awkward but doable.

Phil