C5 1.6 HDi Is there a low pressure in tank fuel pump?

[NutsAndBolts]

On my C5 1.6 HDi mk2 (2007), there are 2 electrical connectors which plug in to the top of the diesel fuel tank (Accessed through a circular black plastic panel under the rear seats - Note this panel should be prised off and not turned as it has cables clipped to the back of it).
I think that one of the connectors goes to a float sensor which detects how much fuel is in the tank. (When the connector is removed, a resistance can be measured between the two pins on the top of the tank)
I would appreciate any help to understand what the other connector is for. My initial thoughts were that this was to a low pressure electrical fuel pump.
When I removed this connector and measured the resistance between the two pins on top of the tank I found that it is open circuit. I then measured the voltage between the two sockets in this connector and when I open the drivers door it reads 12Volts for a short period before returning to 0Volts. This again sounds like the behaviour of a fuel priming pump.
However when I contacted Citroen spares they advised that they don't sell a priming/low pressure fuel pump and therefore don't think there is one!
I also had a look on the Citroen service website: http://service.citroen.com" onclick="window.open(this.href);return false; and can confirm that a low pressure pump is not available there.
Note: the service.citroen website can be a good resource. You have to create an account to login - then you can get a list of parts and their costs bases on a VIN. You can also purchase the ability to read car technical manuals and log a ticket for help with resolving a problem (though I haven't tried them out yet).

So my questions are:
1. Does my C5 Diesel have a low pressure fuel pump or does it run purely off the mechanical high pressure pump on the engine?
2. If it does have a low pressure fuel pump then where can I buy a new one as I guess mine is broken (open circuit)?
Also will the car run without a working priming pump?
When does this low pressure pump run - is it only before you start the engine or does it run all the time or perhaps it kicks in at certain rpm?
3. If not then what is this thing in my fuel tank that is open circuit and gets a 12V feed?

[wheeler]

There is no low pressure pump in the tank, this can be confirmed if there is a hand primer in the engine bay. On models that do have a electric pump in the tank the wiring for it is normally in the same connector block as the sender which is normally a 6 way connector with 4 wires in it, cant think what the second connector is for, can you post a pic ? be aware that your car may have the wiring present for the fuel pump and it also may have power to it as the looms can be generic. This is certainly the case on Xsara HDi's, later models changed to a Siemens injection system & done away with the in tank pump although the wiring & power feeds are still present, the tank units look almost identical apart from when you unplug it & there is on 2 pins in the unit rather than 4. This can often lead to misdiagnosis of a faulty electric fuel pump, the problem with that is the person checking it will order up & fit a fuel pump when there wasn't one there in the first place, the problem with that is it usually lasts no more than a week before the hand primer bursts.

[NutsAndBolts]

Thanks Wheeler. That has saved me a lot of trouble. My car has a hand primer in the engine bay so there is definitely no low pressure pump then. As you say, my car must have the wiring present for a pump but perhaps this is just terminating at a dummy connector on the top of the fuel tank. Thanks again for your help.

[citroenxm]

Dont think ANY 1.6 DV6 engines had a lift pump as its built into the Engine pump as per older XUD type setups..