XC90 fuel pump replacement
There are plenty of guides online for this but I found them all lacking for the 7 seat version. One even suggests removing the 3rd row seats, another shortcuts this by cutting the carpet (!). Volvo says leave it in place and fold it out of the way.
The best tutorial is here volvoforums.com/forum/volvo-xc90-9/xc90-fuel-pump-replacement-tutorial-70880/
There's a 2003-2005MY recall in the US with the Volvo replacement instructions here www-odi.nhtsa.dot.gov/acms/cs/jaxrs/download/doc/ACM14888311/RCMN-09V483-9234.pdf
Apparently the pump was designed specifically for the southern hemisphere where liquids go down the plug hole the right way. Only pumps in the US fail presumably since this natural phenomena is reversed. This explains why there is no recall in OZ.
I'm not sure how mine spent enough time in the north to cause this defect to manifest itself in a vehicle delivered to OZ (!)
Access to the pump is poor with the carpet in place and it all needs to be cleaned to prevent dirt entering the tank.
To improve access, I removed the rear floor carpet without removing the third row of seats. It needed a thorough clean back there anyway. To do this:
1 - remove the front row of bolts (3 off) 1 under each seat and 1 in the centre (visible in photo below)
2 - lower seats. The two bolts each side (rear) are just accessible with a socket if you deform the trim slightly first.
3 - loosen the rear bolts using a socket (6 off) 2 each side and 4 in the centre (visible in photo below)
4 - raise seat backs
5 - lift the front of the frame (note short extension bar in photo below)
6 - remove carpet

This added about 30 min to the whole job. Volvo Service Bulletin says 2.3 hours. I'd suggest you allow 4 for the first time with cleaning.
FCP Euro delivered the pump in 5 days (thanks Philia bear). BOSCH OEM - check your VIN chassis number.
Also order the removal tool or be prepared to invest time in manufacturing one out of a 100 DWV socket and more time making it work in the confined space.
The best tutorial is here volvoforums.com/forum/volvo-xc90-9/xc90-fuel-pump-replacement-tutorial-70880/
There's a 2003-2005MY recall in the US with the Volvo replacement instructions here www-odi.nhtsa.dot.gov/acms/cs/jaxrs/download/doc/ACM14888311/RCMN-09V483-9234.pdf
Apparently the pump was designed specifically for the southern hemisphere where liquids go down the plug hole the right way. Only pumps in the US fail presumably since this natural phenomena is reversed. This explains why there is no recall in OZ.
I'm not sure how mine spent enough time in the north to cause this defect to manifest itself in a vehicle delivered to OZ (!)
Access to the pump is poor with the carpet in place and it all needs to be cleaned to prevent dirt entering the tank.
To improve access, I removed the rear floor carpet without removing the third row of seats. It needed a thorough clean back there anyway. To do this:
1 - remove the front row of bolts (3 off) 1 under each seat and 1 in the centre (visible in photo below)
2 - lower seats. The two bolts each side (rear) are just accessible with a socket if you deform the trim slightly first.
3 - loosen the rear bolts using a socket (6 off) 2 each side and 4 in the centre (visible in photo below)
4 - raise seat backs
5 - lift the front of the frame (note short extension bar in photo below)
6 - remove carpet

This added about 30 min to the whole job. Volvo Service Bulletin says 2.3 hours. I'd suggest you allow 4 for the first time with cleaning.
FCP Euro delivered the pump in 5 days (thanks Philia bear). BOSCH OEM - check your VIN chassis number.
Also order the removal tool or be prepared to invest time in manufacturing one out of a 100 DWV socket and more time making it work in the confined space.
Comments
This video shows the locations.
https://youtu.be/wyzeK1cEaxY
Remember you only need to remove the bolts to free the carpet - not all the side trims.
I've posted pics of the slides that I think you are talking about. I also posted the slide where it talks about removing the cover to access to the 2 outside rear screws. I think that is the cover you stated you can deform slightly to gain access.
https://www.fcpeuro.com/products/volvo-fuel-pump-assembly-s60-v70-xc70-s80-xc90-bosch-30761742
&
https://www.fcpeuro.com/products/volvo-fuel-tank-lock-ring-wrench-s60-v70-xc70-s80-xc90-cta-2493
From FCP..
Question: (Posted by: nxxx2@gmail.com)
Does this fuel pump come with a new o-ring or does that need to be purchased separately?
Answer: (Posted by: FCP Product Team)
The Fuel Pump O-ring needs to be purchased separately. For Plastic Fuel Tanks the part number is p/n 9183708 For Metal Tanks the part number is p/n 8634839 You'll need two of whichever seal you need depending on your fuel tank.
I usually zip tie a 1 metre length of hose to the wiring/fuel line to make it easier to re-route when fitting the new pump.
One thing he wants to do is run the car for a little bit afterwards to ensure there are no fuel leaks.. this is great and I'm glad he is going to take this extra care step.. but what does that do to the air bag system when there are no back seats in and the seat sensor wires disconnected? I'm going to guess and say it'll create error codes that'll need to be cleared.
Give everything including the the top of the tank a good clean first otherwise it'll end up in the tank.
Make sure you have good ventilation.
I'll ensure the sunroof, all doors and back is open for him. I don't think he smokes.
Also dont let the o rings get fuel on them or they will swell up
The fuel pump has possibly been changed before. The underlay has been cut. I pulled the carpet out anyway following the procedure and left the underlay in place and folded over the cut section.
The fuel pump looks fairly clean. However the sender unit on the passenger side is where it's obviously been weeping. Not impressed.
..Now my anxiety is high about benzene exposure. Someone make me feel better.