The fact that the solenoid is not clicking indicates that either you do not have enough power to move the solenoid (back to battery, cables, cable clamps and ground straps) or the low amp signal from the ignition switch to the solenoid is not happening. There is nothing here to indicate a bad starter yet.

Did you jump the car with negative cable to some part of the chasis or to the negative battery terminal? If you can get the chance, hook the negative cable directly to one of the grounding points on the engine and try again. This all but elliminates cables, clamps and bad grounds if the car does not start.

Now if the clutch switch is similar to American vehicles (likely) it will have two wires; one from the position III of the ignition switch and one to the starter. You can jumper it by unplugging the connector and sticking a paperclip in both connectors. WARNING! I do not have a wiring diagram on this car or any Volvo with a clutch switch so this might be wrong advice. Now try to to start the car. This eliminates the clutch switch from the trouble shooting.

Now we are down to two basic possibilities; ignition switch/switch wiring; solenoid/big positive cable to the solenoid. Now a brave man can bridge the terminals on the solenoid with an insulated screwdriver or attach the positive jumper cable directly to the lug where the big red cable goes into the solenoid. Before you do this make sure the small red wire is connected firmly to the solenoid because I still think you are not getting the low-amp signal from the iginition switch to the solenoid. Either of these brute force methods of testing the solemoid may have negative effects on the sensitive electronics in you car so test at your own risk. I have never fried anything this way, but that ddoes not mean you won't.

The reason I asked about the keys is that all my old 240's had a bad ignition switch due to owners carrying 5 pounds of key on their chain. This can cause a host of phantom, intermitent problems.

Good luck!

Onkel Udo