Rear tank not filling properly
 

The rear tank on my truck is not filling properly. I have to sit there and babysit the pump other wise it will keep shutting off. It seems as though the tank isnt venting as it is filled cause the fuel will back up and slowly "glug" down. I have looked and cant find a tank vent. can anyone tell me or better yet have pictures of what I need to be looking at to fix this issue.

Truck is a 1996 F250 single cab long bed 2wd diesel.

Don't have pics but vent is on top of the tank. To find it you have gain access by removing tank or lifting the bed. My front tank just had that problem. Se nding unit needed replacing as well I lubricated the vent and all worked like when new. It may come back on me but will give me time to find new vent found one but really pricey.

The vent on top has no impact on filling. The filler tube/neck is one pipe inside another. The fuel goes down the inner pipe and the air it replaces comes up the outer. See that little curved hole at the top of your filler pipe, just inside the cap? That's where the air vents out while filling.

This is a very common problem with the PSDs. Options:
* Expand that curved hole - I pried mine out larger with a screwdriver, and it helps, SLIGHTLY.
* Bring a 4x4 block and drive the LR wheel up on it at the pump. This puts the filler neck at a more favorable angle for venting. Yes, there are guys who do this every time they fill up.
* Look up "fast fill mod" on the diesel forum sites, and in the PSD section here. This is a mod that DOES employ the tank-top vent. In a nutshell, you remove the inner pipe-within-a-pipe. Then put a pipe fitting in place of the vent/cap on the top of the tank, and weld a bung to the filler pipe up by the cap, and put a hose between the tank top fitting and the bung. That hose becomes the air-out vent. You'll need to find the thread(s) for full detail.
* Try different positions of the nozzle, different pumps, different stations. That restrictive venting system is very picky.

I agree with most of igned to work. However,what you have said and yes it is true that is how the system is designed to work. However, when you take the filler neck off and nothing is misaligned. Or clogged for any reason there must be another reason for this to occour.
The vent at the top of the tank works to follow air to escape as well. This vent is pressure sensitive as far as I have been able to determine. I am not sure exactly how this works in conjunction with the top vent. But I know this for sure, if you remove this vent gas will flow in freely.if this vent is cleaned and replaced it will still flow freely. This happens without doing anything else to the tank or the filler hose.
With this method there is no welding or messing around with parking on an angle or filling the tank slowly.
I have performed this "cleaning" and I know it works. Why it works I'm not sure. But it does work!
The only point I am making about this is that when the vehicle iwas new there were no issues with filling either tank. Why? There was no parking on a block or moving the nozzle to achieve proper filling of the tank. Why?
The only thing I can say is that the two vents work together to allow adequeate amount of air to escape during the filling process. But, over time something changes and slowly filling issues come on. This cleaning of the vent returns it to the new status and no issues with filling. How long it lasts is another matter!
Not trying to create an argument but I feel that there is no need for welding etc if this Vale is cleaned or replaced. Just how long will this last is the question. From experience this cleaning lasts a pretty long time. Replacing? All I can say is that it took 26 yrs to occur before the tank would not fill.
Now this may not work for all years but it dues work on 93 to 96 models.
I also want to state that this may not be a permanent fix! But it works!! On this i am sure. How do I know this? I am driving it!!
Further discussion welcomed!!

"Gas" better never flow in, or out of, any part of the OP's truck. That would be a Very Bad Thing. Have you had your method work on a diesel truck?

No I have not used this method on a diesel.thought this was on a gas model.
But I have seen on diesels that the vent on top of thtank is taken out and drilled out. Don't know if this worked or not was just told that it would take care of the prohlem.

Mine does the same thing only on the front tank. I have to "squeeze in " the fuel and it's really annoying especially when itshe cold out.