My wife has a '19 3.5 EB and this am tried to put fuel in with a little less than a 1/4 of a tank. The pumped kicked off, she thought too soon. She got in and it was about 1/2 a tank. She tries again and it kicks off spewing a little gas, like it was full. She tried fueling very slow and same issue. She ended up with the 1/2 of a tank. There did not seem to be a pressure build up, according to her. What would cause this? Truck wasn't running and has 5800 miles, so it has been fueled a time or two.

 

Maybe the fuel pump itself was faulty.

I’d try another fuel station before messing around with the truck itself, since it’s a simple thing to rule out at least

 

I’m with Seville009 on this one.

If this hasn’t been an issue for those first 5800 miles, I’d strongly suspect the issue is with the gas station pump, not the truck.

 

If it does this at another gas pump, the carbon canister is likely fuel soaked and the vent line is clogged.

This is caused by overfilling the tank. When the pump automatically shuts of when filling the tank, don’t force more fuel in. I’ve seen people pump and click several times trying to force that last gallon in unaware of the damage they are doing.

 

My first suspect was the pump, but she says it seems normal and that is why I asked. We'll try another station and see what happens. If it is the carbon canister, will it clear itself up with evaporation of the fuel?

 

No, it’ll have to be replaced. Never top off. When the pump clicks, it’s full.

 

I am looking at the same problem with a 93 351 bronco. It just started and I know it is not full (after new fuel pump at Ford dealer, the guage quit on 2nd day). No matter how easy I try to trickle fuel in, the pump clicks off. Did it at 2 different stations. The bronco cranks and drives fine. Looking at LMC catalog, there is a 2 port valve behind the fuel pump plate, probable the same type on later models---or close. LMC prices the 2 port at 119 bux, so it is more than just an open vent. I suspect it has a float inside that functions much like a carb float. It the "float" sticks up (like it would if the fuel level gets too high in tank) It would shut off raw fuel to cannister and other tank vent line. LMC also shows a 1 port valve that is cheep. If that valve is stuck closed, tank can pressurize at any higher but not full and not allow more fuel to be pumped.
I am doing the cutout over the tank, large enough to access the vent valve. I have already done it and it went very well, more on that later. I also need to pull the fuel pump plate to look at the connections to the float itself. The pump works fine. Hopefully someone on here know about this valve or has pulled it out. Maybe something like this is what the original poster is experiencing...even on a much newer vehicle.

 

That should be covered on the federal emissions warranty, if it is a defective canister.

 

It looks like it was just a pump gone wild. After we refueled yesterday at a different station and it went normal, I called the other station. The person on the phone told me they had to get one of the pumps worked on the other day. Thanks for the ideas.

 

FWIW on the overfill--I badly overfilled mine once, ran gas out of it. I did not get a CEL or have any issues at all.

So maybe that EVAP system will give you one.....

I go with auto stop for the most part now.

 

Me thinks she did not seat the nozzle in the capless fill neck all the way.