I've received some responses to this problem on my '87 740 Turbo (199k miles), but haven't isolated the problem yet.

When the car is warm-- 10 minutes at idle, taking 5 minute drive-- it won't start. I've changed the main fuel pump (got it cheap, so it seemed like a good idea), filter and pump relay, and there's no gas in the vacuum side of the fuel pressure regulator. Also cleaned the connectors at the radio suppression relay, and an unknown (brain?) relay in the trunk. (Not shown in Haynes, as I can find. But I've usually found Haynes basically useless aside from routine maintenance issues.) So now I'm thinking there is a sensor or other relay problem causing this.

However, the car always starts when cold (air temp under ~50 degrees F) AND has sat for a good 6-8 hours. But yesterday: car sat all night, temp around 50, but would not start when I went to work on it, around 65 degrees, balmy for this time of year. The passenger side of the car faced the morning/early afternoon sun, and even after nightfall and a 10 degree drop-- nothing. It's back up to 55 this morning, and it fired right up.

Though they look clean I'm re-plugging it today, and will check for leaks at the intake manifold (thanks FAQ). I'd like to check/replace the following, but I'm not sure where they are (again, either no useful pictures in Haynes of the issue was not addressed at all):
Cold start injector
Power stage
Hall sensor (found, but not easily accessible)
In-tank fuel pump (I can't disconnect the electrical-- suggestions?)

I've done basic maintanence and other small repairs in the past--rebuilt and reinstalled slave cylinder (works great), blew two belts and replaced them no problem-- so I'm confident of being able to do this work. This is my second Volvo (drove an '85 240 to 223k) and the first one I've worked on myself, thus I find the help from pics/schematics/etc a very useful tool.

Thanks for any help.
Tim