fuel pump relay

Hi all

I have a 51 plate 1.6 Zafira. Whilst driving on the motorway last friday the engine just cut out. I pulled over and the car then started fine and drove another few miles when it did the same. The green flag recovery man put the diagnostic computer on and it came up with "fuel pump relay open circuit" we could not get it going so i was towed home. I have got a new relay but this doesnt solve the problem. the engine will run fine for a while then just cut out. The mechanic said the relay was the pink one (number 3) under the bonnet. which is the closest of the two pink ones when you look in the engine bay. I bridged this relay and still had the same problem. So I shorted the second relay (the second pink one, the one furthest away from the front of the car, no 4) and the car runs fine. it seems this is the one that supplies the power to the fuel pump. So i think i have found the problem but cant work out what is causing it. whatever tells this relay (no 4) to switch on is switching it off for some reason. Can anybody suggest what might be causing this problem. Also can anyone tell me what relay 3 & 4 actually do????

oh dear!!!!!update


I have just gone to start it and i heard a clunk and wouldnt turn over. All it does now is a whizzing noise when i try and start it. Maybe the fuel pump relay was turning off as a safe guard. Anybody got any ideas??
PS i have just checked and i had the timing belt changed at 90000 and it has currently got 99k on the clock

Ok , i have had a new starter motor fitted, which seems to have been an unrelated problem. Just unlucky.

I still don't know why the fuel pump relay is switching off?

Anybody got any ideas what controls this and why it's being switched off?

Update

I have now tested the 12v supply to the relay. I have 12v supply when the car is runing but when it cuts i only have 0.1 volts. I have tested the 12v to the relay direct to the battery and it shows 12v - so the supply is working but the earth is off. any ideas what would cause an intermitent earth to go on and off ?

After about 5mins i then saw the voltage grow slowly over about 30secs back to 12.16 v

I could wire an earth direct to the relay which would proberbly solve it but i would like to know why its doing it and if i bypass this earth direct will it cause a problem. Is it the engine management switching this earth off?

can anybody help????!!