Had my v70 for about ten years now and had this problem for 5 of them. Most times it turns over, fire and stops. Thought it was either fuel starvation or immobiliser. Would the immobiliser allow it to even fire?. Checked fuel pump relay and fuses. all ok. Once it does start, its fine. Its never actually failed to start eventually, but sometimes takes 5 or 6 attempts. Any ideas? My local mechanic put his test equipment on it recently and all readings were good. (And of course it behaved perfectly while he was there!!.)

 

When was the last time the car was at stage 0? New plugs, cap, rotor, wires, filters, etc?

 

Just had new plugs, cap,wires, rotor. Filters about 6 months ago. No improvement.

 

Check fuel pressure before starting, while it's running, and 30 minutes after you shut it off.

 

Might be a exhaust cam sensor failing...

This is commonly overlooked. Might be worth inspection.

 

I had the same issue and went to a dealer and had the diagnostic done and replaced a few parts and kept having problems until the only code coming up was immobilizer however like your situation, it worked fine every time i took it in to the shop. The service dept. suggested next time I try my other key because sometimes it is the chip inside the key that goes bad, so you probably just need new keys. They also cleaned the connections to the immobilizer but that has to be done by a volvo mechanic.

Good Luck