Since the end of June(!!!), my 780 doesn't start anymore. My wife (Volvo 740 1990) had such a problem in Mai this year, which could be solved (no power at the fuel pump relay, jumpered to drive to the garage, module changed (700$ !!!).
My 780 was in the garage during our summer holidays. When we came back, i tried to start, but didn't succeed: The starter was cranking, but no start. Sometimes it started, but died after about one minute, after changing from Park to Drive. Now it doesn't start anymore. I remembered the problem of my wife's car and jumpered the relais (30 to 87-2). The fuel pump runs, the engine cranks, but doesn't start. Then I read my books (Haynes and Chilton), knowing that the 780 is technically equivalent to the 760. No idea how to proceed from there (except the electrical schemes in Haynes). Then I read the FAQ's in brickboard and tried some of the hints, but still no start. Then I started to interchange the known good parts from my wife's car to my car (radio emission relay and fuel pump relay, but still no start). Then I switched the ignition power stage from my wife's car and everything worked just fine. The old power stage had no more contact to the fender and must have got to much heat (I thought). I (virtually) run to the shop, bought a new power stage (200 $ !!!), went home, switched the part and tried to start the engine: No start!!! (My dad told me, that with a small chance you even get a dead original part at the volvo dealer). The next weekend, I switched all the three power stages. All three work just fine in the car of my wife, but with all of them, my car doesn't start (now). At the moment, I can't move the car to a volvo expert (most of the electrical components are open, the interior looks like a battle field). So I decided to look for professional books. As the original manuals are very expensive in switzerland and as a computer pro, I decided to look for a copy of the VOLVO VADIS-System (CD's or DVD). I ordered a set of two cd's in Poland. After a week, i got the cd's, with an installation manual in polnish. Some days later, the guy sent me a short manual in english. After some days i knew, that one of the cd's was defect. At ebay, I bought another copy of a dvd. This one came with an excellent installation manual. I tried to install the software at my home, but no success. I tried to install the software at my office, but no succes. Last weekend, I succeeded in installing the VADIS System at home. I looked for a troubleshooting chart (starting problems etc.) but found nothing. There is a lot of information about newer cars (1994 and up), but only a few about 760 or 740. I finally ordered a troubleshooting manual (hard copy), but i have to wait about a week. Today i first thought about selling my 780 (when it runs again), but i don't believe, that i can do this. It is to nice to look (italian design) and the best Volvo i ever had (220, 144, 240, 740 and now 780). Please help !!!

Perhaps it may help when i tell you, that the garage was cleaned during our holidays and it was very damp for about a week.

Perhaps somebody out there nows the special symptoms: The engine cranks and after about ten turns, there is a sudden stop (like an ignition spark at a completetly wrong time). There is no hall sensor in this car (it has the newer sensor at the flywheel which is said to be better). The tacho moves, when the engine cranks, but only very small "pulsed" movements (By the way, how many rpms should the tacho show during cranking?).

When I turn the ignition on, the valve over the inlet hose has a strange sound (to me). It sounds like opening and closing all the time. Perhaps this is another hint for one of you.

What i haven't tried before is the diode-resitance test mentioned in one of the articles to read out the error codes. Perhaps because i hope that i don't have to change one of the heavier ($$$) modules in the passenger compartment...

Thanks a lot for every hint or idea.
David