So my car is 2013 XJ supercharged but I think it would be the same on XF 5.0 sc cars. Looking for a simple way to rewire maybe through the fuse box for auxiliary pump to be on with ignition instead of engine on. This might help somewhat with cooling when I am at the drag racing track as heat soak is quite an issue waiting around for the next run.

 

The pump is controlled by the ecm via can bus, actually I was under the impression that the pump turns on if the SC is getting too hot, regardless of engine status. But I might be wrong on that.

According to page 42 of the 2012-2013 XF wiring.pdf, relay 18 does switch the aux coolant pump via fuse 40. The relay feed is on B+ and controlled by the ecm, I'd not mess with that. The pump will run constantly if you just bridge the relay, regardless of ignition status. You could do that, but then add a switch and do not forget to turn it off at the end of the day.
Better feed power behind relay 18 by adding a bridge between fuses F40 and F37. That will bypass power from the IGNITION ON relay 19 directly to the aux pump. Please verify these fuses to be sure they are the correct ones. See also page 96 of 2012-2013 XF wiring.pdf
Fuses 37 and 40 are both 15A, but with the bypass you basically add F40's load to F37 and its cabling. The cables are probably ok to take the extra load, but you want to make sure to connect your bridge on the 'hot' side of Fuse 37. That way its just on the cabling and not on F37. Bring some extra fuses with you anyway.

The relevant wiring diagrams are on page 42 and 96 of the 2012-2013 XF wiring.pdf found in this forum (I believe).

Chris

 

Adding to this thread because my '15 R-S has something a bit different (no wiring diagram I have seen yet reflects my exact setup).

My pump has 3 wires. I have performed continuity tests for each by looking at RRS, Ftype, and XF diagrams and have come up with the following.

Pump:
Pin#1 - Black wire, chassis ground
Pin#2 - Brown wire, ECU Pin#55
Pin#3 - Yellow/Green wire, goes to Fuse #40, which goes to Relay#18
Relay#18, pin#2 ALSO goes to my ECM, pin#35.

So in my car's case, it appears I have a ECM controlled relay18 like Chris has described, but also another ECM connection at the pump itself. I have asked around about this a lot and I am not getting much info. The 2019 RRS diagram shows this 3rd connection as a "PWM" likely to mean pulse width modulation, at the pump and "O_S_CACWPR" label at the ECM. My goal is to figure out if I can run the Bosch Pump which only has two wires, but with an ECU that might be looking to manage variable flow im wondering if I need to cancel this idea, seems like I might be in rare/unchartered territory.

@AlexJag not sure if any of this helps you, it might if you also have a 3-wire pump, but it appears later cars have some additional control potential.

 

From what we are seeing I "think" it's the 2015 cars and up that have the 3 wire IC pump. I have a 2014 XJR and it's a 2 wire setup.
Interesting to see how this 3 wire pump compares to the Bosch 010 or the Johnson C-30 pumps too.

No one here uses it but the Johnson pump has replaced the Bosch unit for a lot of MB guys with AMG cars.
It's a good bit more expensive at almost $200.
Johnson C-30 IC pump
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Anyone here have a 2013+ Bosch (8speed) 5.0 car that can measure your intake temps?