When you serviced it, what did you set the plug gap to? Should be 0.65-0.7mm.
Next, what are you like using a multimeter? If you're ok, locate the CTS (Coolant Temperature Sensor) located more or less under #3 inlet tract on the head. The one inf front sort of between #1 and #2 is the temperature gauge sender - don't confuse the two!
The CTS has two terminals, each goes through a thermistor inside the sensor to the body of it which also happens to be earth so make sure no bright spark has wrapped PTFE tape round it!
Check from each teminal to earth is about 2.5k Ohms +/- about 10% (2200 - 2800 ish) when cold and that the resistance between the two pins is about the sum of the two separate resistances. If it's within those ranges then the CTS should be ok. Further information can be found on Pg20 (by document viewer page number) of this pdf :
http://www.myvolvolibrary.info/Tech_...DataPocket.pdf
Also worth checking the carbon brush inside the dizzy cap, these can easily break if the fitting of the cap was a bit ham-fisted.
Also while cranking, do you notice if the rev counter flickers very slightly or not? If it doesn't, there's a good chance the CPS (Crankshaft Position Sensor) is faulty. THese aren't expensive and are fairly easy to change if you lift the bonnet vertical and have a reasonable reach on you. Being at the back of the engine bay, the wiring is subject to a lot of heat which does the insulation no favours and eventually cause the wiring to break and/or short together, rendering the output nil.