About a year ago my '92 960 started a wierd deal. It would die while driving but then restart after 10 or 20 attempts, then run fine. This would happen infrequently, maybe once a month or sometimes several times a day.
I couldn't find anything wrong. No codes and of course it never acted up while I was working on it. After getting advice from this group I resoldered the circuit board in the fuel pump relay. The car ran fine for about a month, then started the same thing again.
After a few months it got worse. It would die almost every time I drove it, usually 2 or 3 times in a row, then run fine.
I took the fuel pump relay apart again and found cracks in the soldered connections that I had previously resoldered. The first time I did it I didn't add any solder to the connections, just melted the solder. I guess that was a mistake. The solder connections were paper-thin and recracked. This time I added a drop of solder to each connection. So far, so good.
So, if you resolder a circuit board, add a little solder to each connection. Of course, don't use acid-core solder and be sure to get the connections hot enough for the solder to flow freely but not hot enough to burn the circuit board.
Steve Elms