Fuel pumps shuts off while driving

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
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Smart to immediately notice no fuel pump sound and then test and by-pass the fuel pump relay. But these relays become intermittent - tap them and they work - for a while - and then they fail again. They seem to get "tired".
There's another relay that you should also check. The "over voltage protection relay" (it has a fuse on its top) can cause strange things to happen - hard starting, rough running and then perfect running etc..
If the OVP relay is proven to be OK then I'd suspect the fuel pump relay or the pump itself.
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T.G, The pumps are Bosch one year old, could they fail that early? Yes, the OVP relay as you suggested, I want to check it out. Thanks
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Odds are that one year old Bosch pumps are OK.
How about that fuel pump relay? One year old???
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T.G. Lambach wrote:

TG, I don't know the age of the pump relay I never replaced it since I had the car. However, It seems OK when I tried it on my friend's 560.
Saeef
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It could be intermittent. I would replace it.
Marty
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In that case I'd make the fuel pump relay #1 suspect.
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I have replaced the fuel pump relay with a new one. Thanks to all who proided me with feedback.
Saeef
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The relay still seems like a likely candidate for this kind of intermittent issue. I would replace it personally.
Marty
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