Defying the laws of physics

I have a strange issue with the petrol pump on Bertie, our 1994 Punto Cabrio. The pump has stopped working, but there is not a problem with the pump, I have a spare which I have tested off the car, but when I connect it, it doesn't work. I have tested the live feed to the pump and it is fine, it becomes live when the engine is cranked, which is correct. I have also checked the earth, which again is fine. However, when I connect the pump the live feed goes dead. Disconnect it and it is live again. It seems like the car recognises when the pump is connected and kills the live feed.
I have posted a thread on the Punto forum and Facebook page, but as the car is not a GT and I am not lowering the suspension or painting my wheels nobody is able to assist. Commer owners, however, are a helpful bunch and have assisted me with this car in the past. Any ideas?
 
Google suggested phrases says pump relay. Could that be faulty?
Yes, I considered that. There are two identical relays, one for the pump and one for the ignition circuit, so I swapped them, but it made no difference. However, I think you might be onto something.
 
There is a resistance somewhere on the live side that let's the colts through but not the amps. Start by cleaning any contacts in the relay and switch
 
I'll have a go at cleaning the relay contacts tomorrow. I knew I would get more help here than anywhere else! If I fix it, I shall get the suspension lowered and paint the wheels.
 
Not much help I'm afraid, but my son just had a Punto diesel multijet and I had to fix the turbo, the blown door speakers and a delaminating silencer for the MoT:rolleyes:
Edit-obviously not speakers for MoT.
 
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I have a strange issue with the petrol pump on Bertie, our 1994 Punto Cabrio. The pump has stopped working, but there is not a problem with the pump, I have a spare which I have tested off the car, but when I connect it, it doesn't work. I have tested the live feed to the pump and it is fine, it becomes live when the engine is cranked, which is correct. I have also checked the earth, which again is fine. However, when I connect the pump the live feed goes dead. Disconnect it and it is live again. It seems like the car recognises when the pump is connected and kills the live feed.
I have posted a thread on the Punto forum and Facebook page, but as the car is not a GT and I am not lowering the suspension or painting my wheels nobody is able to assist. Commer owners, however, are a helpful bunch and have assisted me with this car in the past. Any ideas?
Scrap it
 
Never ever heard of a duff speaker failing an mot, somebody is at the wind up, I would be taking it else where.
 
Bertie lives again!
Many thanks to Paul for pointing me in the right direction. I knew the relay was fine as it also serves the injectors which I knew were working, so I traced the wire from the relay to the connector where it joins the fuse box. A little wiggle and it came alive. It was obviously not making a good contact and as Paul suggested, I was getting the volts, but not the current.
Now to look for some lower springs, big bore exhaust and silly wheels!
 
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