Difficulty refueling both our XC70 T6s

I'm used to the frustrating process of refueling our 2013 T6. The pump shuts off just seconds after getting fuel flowing. I have to hold the filler nozzle, and lightly squeeze for about 1/2 the flow rate to prevent automatic shutoff. Even with that, it'll shutoff 10 times during a refill. It takes way too long. I've been planning my next steps....to borrow an endoscope/inspect the filler pipe, and test the EVAP Canister Shut-off (vent) solenoid valve to make sure it is still passing air (normally-open).

Today, our other T6 (2015.5) did the same thing! Two cars with essentially identical everything mechanical -- and the same fueling problem?

I've had the 2015 about 6 months, and have refueled it maybe 2 dozen times....this is the first time it balked.

I wish I knew more about how the shut-off mechanism is triggered on the pumps (Arco). The shut-off works fast when the tank is truly reaching full, but something is
making it think the tank is already full prematurely. Does anyone else have this problem? Suggestions?

Fuel filler nozzles use a venturi system to shut the trigger off. Fuel backing up to the venturi is supposed to shut the trigger off. A build up of air pressure could do the same thing.

Sometimes where you hold the nozzle in the filler neck can make a big difference. More difficult for you in CA with vapour recovery systems. Don't remember if all of CA has them but I do remember they can be a pain in the backside.
Try holding the nozzle at a different angle or distance in to see if it changes the fill.

(HowStuffWorks.com "The Automatic Shut Off"):

When the customer removes the pump handle from its place on the side of the dispenser, this action activates a switch that starts the dispenser operation. (In some cases the switch is spring-loaded and activates automatically; in others, the customer must raise a small lever manually to begin the process.) At that point, the customer simply inserts the nozzle into the car's gas tank and pulls the lever. Stopping the flow of gas is just as simple -- the customer need only release the lever to cut off the stream of fuel.

But what if the tank fills unexpectedly to the brim and the gasoline threatens to overflow? As anyone who's ever operated a gas pump knows, the pump will switch off automatically. But how does the pump know when to stop pumping?

As the gas level in the tank rises, the distance between the dispenser nozzle and the fuel grows smaller. A small pipe called a venturi runs alongside the gas nozzle. When the end of the venturi pipe becomes submerged in the rising gas, it chokes off the air pressure that holds the nozzle handle open and shuts down the flow of gas.

Unfortunately, this shutdown can sometimes happen before the tank is full as the rapidly flowing gas backs up on its way into the tank. This can cause the gas handle to spring open before pumping is complete, leaving the annoyed customer to squeeze the handle again and risk the possibility of overflow. Pausing briefly will allow the gas to continue into the tank and the pump nozzle to start pouring gas again.

I'm in CA and just becoming aware that I'm dealing with 2 generations of vapor recovery engineering at the same time:

OBVR. The original OBVR (On-board vapor recovery) concept was, as the fuel tank is being filled, shift the air/fumes displaced into a charcoal canister with a vent open to the outside so the fumes can flow into the canister. The charcoal soaks up the fumes, and then when you're back on the road, a purge valve opens and the engine sucks in these vapors and burns them. The idea was to make vapor recovery completely self-contained in this EVAP system, which was further evolved to detect fuel vapor leaks.

EVR Phase 2 (in CA). The entire gasoline delivery system, from refinery to vehicle, is one giant 2-way path with gasoline flowing out and fumes flowing back. For instance, when the fuel transport truck fills up, its air/fumes are sucked back into the refinery. When the truck is filling underground tanks at your local gas station, the hose is 2-channel, pumping gas out and sucking back in air/fumes displaced from the underground tank. The last 6 feet is the gas pump, which contain the main pipe and a smaller vapor suction pipe. Active suction is applied to the recovery tube -- you can see a small hole on the side of the nozzle where fumes are being sucked in. The auto-shutoff of the pump is monitoring the vacuum on this return line, and will see it dip slightly when the liquid level in the car's filler pipe rises to cover up the hole.

That's the theory.

EVR Phase 2 was implemented in CA in 2009, but there were exemptions for smaller gas stations.

This just confuses further.

But I think ssicarman is on the right track about where suction hole on the nozzle is located in your filler pipe. And, the flow rate of the gas pump is going to matter, the slower flow rates leading to fewer false shutoffs. There's also the issue of how air flows from your fuel tank to the top of the filler pipe -- there is a small vent hose that "T"s into the filler pipe near the top -- the other end attaches to the apex of the fuel tank. It's hard to imagine this vent path becoming clogged. [How wrong an assumption! See graphic in post #5]

It's been 3 years, and the solution to this problem of difficult refueling has been discovered.
The root-cause of the problem and its solution are posted here:

https://www.matthewsvolvosite.com/fo...p?f=31&t=95306

and the serpentine process of discovery here:

https://forums.swedespeed.com/showth...f-prematurely)

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Originally Posted by ssicarman

Fuel filler nozzles use a venturi system to shut the trigger off. Fuel backing up to the venturi is supposed to shut the trigger off. A build up of air pressure could do the same thing.

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If the Tank Vent Pipe has a clogged filter, inadequate venting becomes the problem. Pumping fuel into the filler throat will raise the pressure in the tank, and air will be pushing back up the filler pipe, slowing the fuel flow rate. If the fuel flow rate is higher coming out of the pump nozzle than the flow rate into the tank, liquid fuel backs up very quickly (1-5 seconds) and floods the Venturi orifice. The gas pump is fooled into thinking the tank is full. This is how improper venting screws up refueling. You can easily get "spitting" of gasoline on your clothes as you withdraw the nozzle -- due to the pressure.