While doing 160 km/hr on my 1991 560 SEC, the car just suddenly died so
I pulled over on the shoulder and tried to restart, no way. I cranked
it 3 times as I remember. I noticed there is no hissing sound from the
fuel pumps every time I turn the ignition to ON. I opened the bonnet
and took off the fuel pump relay. I took the relay to my friend who has
1990 560 and tested the relay on his car, the relay is fine. Thinking
about the problem, I decided to jump start the fuel pumps by external
wire strait from the battery. So I want to the car with the help of a
friend, put back the relay and tried to restart, no way. I ran 2 wires
strait from the battery to one of the 2 fuel pumps. The pump runs.
While me holding the wires on the pump terminals, my friend cranked the
car and here we go, it started. Took off the wires from the pump, the
car kept running. Switch off the ignition and restarted, the car
started fine and no problems since then.
What could have caused the pumps to shut off and not allowed the car to
re-start? Appreciate some help on this as I don't want this to happen
again.

thanks

Saeef