940 having intermittent difficulty starting

[Laney760]

At this stage I'm not sure whether this is a hot starting problem or whether it's confined to petrol starting or applies to both petrol / lpg starting. I suspect it is worse the hotter the temperature is. Edited to say after some research and thinking that my problem is best described as sometimes due to poor hot starting but at other times to starting and then immediately stalling.

On Wednesday morning when the outside temperature was probably about 10 or 11 degrees I started the car up to go to work, no problem, drove just half a mile up the road when I switched off the engine to try and catch a stray dog, got back in the car and she would not re-start. Cranking over fine, nice strong battery / starter but she just wouldn't fire. Left it a couple of minutes, didn't give it any throttle for fear of flooding, eventually she started. Came out of work on Wednesday, the temperature was very high, in the twenties. She fired up immediately but then immediately died and refused to re-start. I gave up cranking it over, sat and waited a few minutes and then managed to start. Didn't use the car again until yesterday afternoon. She started fine in very hot weather but after being switched off after a short journey she refused to start again, took about 5 minutes, again after being left for a few minutes she re-started. Came out of work today in very hot weather, she fired up immediately but then died immediately and wouldn't re-start for ages again, again I had to leave her for a few minutes and re-started without giving her any gas. Just out of interest I went out to the car just now, now that the air temperature is quite cold outside now and she did start up immediately AND kept running but after I turned her off she refused to restart again.

The car had a new Volvo fuel pump just last October. I have eliminated the fuel pump relay, it plays up with it's new (last October) fuel pump relay inserted or it's old working one inserted. The throttle body was cleaned and a new lambda sensor fitted coming up to four years ago now, coming up to 40 thou ago, although I don't recall the hot start problem I had prior to that being like this problem. The car is booked in for full service in October, can a blocked fuel filter cause this problem? The car had a new radio suppression valve last year and a new MAF a few years back.

I have my own code reader, I will see if that brings up a code in the morning. I've just read the 940 FAQ on hot starting problems.

Any advice gratefully received, thanks