Anyone have a trick for tightening the bung nut on a 92 model 940 fuel tank.

I replaced the (In tank) fuel pump and apparently didn't get the nut tight enough because I smell gas fumes when driving the car.

There is no sign of gas leakage, so I know it's fumes leaking from the tank.

Volvo had a recall on the 91 model 940 for this very reason.

I made sure that the fuel pump assembly went in properly and seated in the hole.
The gasket looked OK, but the plastic nut on the plastic tank is hard to torque properly.
I know that there is probably a special tool for this, but I don't have one.

Any ideas? Homemade tools?

thanks in advance
steve