I have a volve 760, if i leave it for more than two days it will not start. I can drain a battery then switch to a new one and it will eventually start, runs badly until warmed up. If i use it every day there are no problems. Any suggestions? My mechanic has been through it and as yet has not found a problem, he's usually pretty good by the way.
I might add that there is a smell of petrol so it may run rich at first

 

What are you missing when it will not start?
Fuel,spark,injection pulse?

 

everything is there, I assume that there is a sensor not doing it's job but which one? It tries to start at first and then nothing, recharge the battery overnight and then it will go, battery fine, spark fine, I suspect it's something to do with the mixture but everything seems fine. I had hoped that this might be a common problem and I wish they had a diagnostics system. It gets to be a pain having to use it every two days, work from home and I resent wasteing the gas.

 

Pull the hose off the fuel pressure regulator and make sure the regulator is not bad and leaking into the intake and flooding the motor.

 

Or you may have a major short which drains your battery over the two days sitting idle.

 

I'm with Tech. I think your fuel pressure are bledding off while not used for a day or two. Maybe a bad regulator.

 

Hi, thanks for those, half term, need I say more?

Pulled of vacuum hose to regulator, no obvious signs there but car not a happy starter after that, did start eventually but sounded like it does after three days. Forgot that when it does restart after period of time, tends to hunt for a bit, runs rough until warmed up and can stall if the pedal is pressed to fast, once it's warmed up absolutely fine.
Battery is fine.
Wondered about fuel pressure but there are two pumps, had one go on another 760, so I assume if it was left for a few minutes the system would recharge, tried that and no difference.

 

Maybe the check valve in the main pump under the car is bad and it is bleeding back from that. Also maybe the main pump is weak.

 

Ok, if you run the car in the am, then let it cool down for more than 4 hours so it is totally cold, then try to start it, will it start ok? I believe those cars have an AIR CONTROL VALVE (like a cold start valve) that controls air input when the car is cold. If that is bad, it may cause problems until the car warms up.

 

I'll get my man to check the fuel pressure, needs to go in at anyrate.

Starts absolutely fine at any time of day or night, day one, day two, dependant on if it's cold or hot, will sart fine and generally OK unless it is cold in which case it might whinge a bit, day three, forget it, might get a fire first time but never catches and after that it's drain battery with not a hint of firing.