FUEL PUMP RELAY

Any ideas where to source a new fuel pump relay for a 1983 GTi (1.8 DX).  I bought a replacement one of eBay, however the new relay is continuously switching (clicking), when the engine is running.  The original part number was 3.300.210.  The one I got off eBay was 321 906 059F.



Any help or advice would be appreciated!

Ta,
Ross

If the relay is O.K. it sounds as though the system isn't maintaining pressure. Why did you replace it. i.e. what was the problem with the relay you replaced? However I am not an expert on these things. I wish I was

The original one stopped working completely.

Looking at your " problem" in more detail and having a think. I believe the relay is triggered from the distributor hall effect sensor, i.e. the relay will run whenever the engine is turning.
I have taken the top off my relay and had a look inside. As well as the relay, there is a 555 timer circuit which switches the relay when a specific voltage is reached across one of the capacitors.
This is repeated ad infinitum whilst the engine is producing a spark. There is no pressure transducer in the fuel circuit to modify the fuel delivery. It seems that once the required fuel pressure is reached a valve opens in the fuel distributor and the excess fuel is fed back to the tank via the return pipe. Therefore the fuel relay should always be running - and will be clicking - whilst the engine is running, and therefore fuel is always being pumped. The frequency of the relay will be dependant on the components in the 555 timer circuit.

This is supposed to be the safety feature I was initially worried about. That the fuel pump wouldn't switch off in an accident - it does rely on the engine stopping tho'. If the engine is still running in an accident it is still pumping fuel at goodness know how many bar

Does anybody disagree with this analysis?

The fuel pump is turned on and off from the Coil circuit for every spark.  I wouldn't think that I have ever heard it
 
Everything you ever needed to know about fuel pump relays:
https://www.cabby-info.com/files/electrical/Relays_Kjetronic.pdf

I don't think the fuel pump is turned on and off every revolution. I think you will find it is kept on by the 555 timer circuit in the relay. The ignition pulses are averaged out in the timer and the pump is kept on whilst the engine is running