totally @ a loss - I need some Expert Advice :-)

[SAZ]

I have 1990 740 GL

[Volvord]

Interesting problem.
The first item I would check and possably replace is the ignition switch, they are prone to failure.

The second item I would check are all the electrical grounds and the neutral safety switch

[LaRy]

Use the interior light as some simple voltage indicator. Check the intencity of the light when trying to start. Of course the light should go down a bit but if it is getting almosts dark, then you have some problem with the battery, the connections to the battery including the grounding or maybe even a short circuit.
As Volvord said, check the grounding, especially the big blue wire grounding the engine going to the battery and after that to the car body. It happens often that it is broken. It also happens that the big red wire going from the battery straight to the starter gets insulation problems causing short circuit to ground. Of cource the problems will be found where it is most difficult to check, at the point where the cable is passing under the front of the enginge, just in that black, almost hidden, greasy dirty place.

[Guest]

Had this on my '66 P1800 and my wife's '92 245. In both cases it was "invisible" corrosion or insulation at the battery terminal. The insulation was caused by an anti-corrosion spray eventually sleeping inbetween the cable connector and the battery post and increasing what should be virtually zero resistance to high resistance. The car would appear dead an instant after trying to start it. Waiting ca 10-20 minutes and it was "live" again (i.e., light would work), but it could be killed by another attempt at starting. Both cases were cured by removing the terminals and thoroughly cleaning/scrubbing all the contact surfaces.

[petershen1984]

Could the above post be from Irv Gordon, with his 3-million mileage Volvo?