Fuel spilling out: A discussion

[Gsmblue]

My recently acquired dually (see sig) is a joy to drive around. But at the gas station she is puking out gas when people try to fill her up. Remember, in Oregon we are not trusted to fill our own tanks!

I have looked around and found a couple of old threads and the docs page:

http://www.garysgaragemahal.com/#nabble-td35678|a35781

http://www.garysgaragemahal.com/fuel-filler-pipes.html

And some posted on other dark corners of the interwebs. This would seem this is a relatively common issue.

I was wondering, what causes this problem and how have people gone about diagnosing/fixing it?

Full disclosure: My dually has an 87+ bed on it so I do not know what type of pipe assembly it has at this point but the fuel caps are the standard bullnose non locking ones and are new as of a month ago.

[kramttocs]

Both tanks do this or just one?

My understanding is that the later years have a better vent ratio.

Both tanks on my 86 fill at full speed- I hit the lock and leave it unattended. My 80 though is a flat bed hack that requires 1/4 speed. Just mentioning that to say that the factory setup does work if working correctly.

I have seen a lot of the vent tubes shoved down or twisted to where the venting is severely restricted. A pain to remove the hose from the tank but I'd start there with an inspection of the inner vent tube.

[Gary Lewis]

Both tanks do this or just one?

My understanding is that the later years have a better vent ratio.

Both tanks on my 86 fill at full speed- I hit the lock and leave it unattended. My 80 though is a flat bed hack that requires 1/4 speed. Just mentioning that to say that the factory setup does work if working correctly.

I have seen a lot of the vent tubes shoved down or twisted to where the venting is severely restricted. A pain to remove the hose from the tank but I'd start there with an inspection of the inner vent tube.

If they kept the '87 fuel filler hoses and used the '84 tank you have a problem. They did that on Big Blue and it was a huge pain to fill the tanks. Somewhere in Big Blue's Transformation thread there's a pic of how those two went together, but it wasn't pretty as the tank wasn't designed for the later vent hose.

[ArdWrknTrk]

'87 & + trucks feed fuel down the center tube and vent in the annular gap while Bullnose trucks vent up the middle and feed around the center tube.

How these two tubes are held in place at both ends means there's going to be a conflict.

While some (especially diesel) Bullnose owners have switched to the later style to reduce the fuel nozzle clicking off, I can't say, and I'm sure Gary knows better (now that he has later tanks in big Blue)

[FuzzFace2]

Both tanks do this or just one?

My understanding is that the later years have a better vent ratio.

Both tanks on my 86 fill at full speed- I hit the lock and leave it unattended. My 80 though is a flat bed hack that requires 1/4 speed. Just mentioning that to say that the factory setup does work if working correctly.

I have seen a lot of the vent tubes shoved down or twisted to where the venting is severely restricted. A pain to remove the hose from the tank but I'd start there with an inspection of the inner vent tube.

My 81 is like Scott's, set is and forget it on both tanks.

It is all in the vent hose I took a lot of time when I worked the tanks to make sure the vents were in place.

You are going to need to remove the filler hose(s) and make sure the vent tube is in the tanks holder and up top before the outer rubber hose is put back in place.

Dave ----

[Gsmblue]

My 81 is like Scott's, set is and forget it on both tanks.

It is all in the vent hose I took a lot of time when I worked the tanks to make sure the vents were in place.

You are going to need to remove the filler hose(s) and make sure the vent tube is in the tanks holder and up top before the outer rubber hose is put back in place.

Dave ----

Great input. On the 84 dually both tanks do this. My other two bullnoses are fine.

I have to drop underneath and check it out properly. I guess whoever put the later bed on half arsed something. I won’t be able to check until the weekend.

[Gary Lewis]

Great input. On the 84 dually both tanks do this. My other two bullnoses are fine.

I have to drop underneath and check it out properly. I guess whoever put the later bed on half arsed something. I won’t be able to check until the weekend.

Let's see if I can do this. Here's the post from Big Blue's Transformation thread:

Well, Scott, it turned out to be a big deal. The fuel tank filler neck that was on Big Blue says "FNF-027" on the side. And if you look that up it is for the later model tank/truck, as shown here on Amazon.

So, I already have one of the two filler necks that I need. So I called the salvage and explained that to them so they are only looking for the rear filler neck. But, I learned that they always cut the hoses, so I will have to replace them.

Which brings me to why BB was horribly slow to fill. In the pic below you see the filler neck that was on BB laying on the Bricknose tank on top, and the correct Bullnose filler neck laying on Big Blue's side tank on the bottom. Notice the size of the hoses protruding from the necks, with the Bricknose neck having a much bigger hose as that's where the gas goes and the air comes up around it. But the Bullnose hose is smaller and corrugated, and it is what the air goes through on a Bullnose.

Then if you look at the inlet on the tanks you'll see the problem. The Bullnose tank has a fitting into which the smaller vent hose is supposed to go. But that fitting is too big for the Bricknose hose to fit over, and too small for it to go into. I'm not sure how they had it in there, but however they had it there was some interference with fuel coming in and the air coming out, and that must be what caused it to be terribly slow to fill.

http://forum.garysgaragemahal.com/file/n69427/Bricknose_vs_Bullnose_Fuel_Tanks_%26_Pipes.jpg

[ArdWrknTrk]

Let's see if I can do this. Here's the post from Big Blue's Transformation thread:

Well, Scott, it turned out to be a big deal. The fuel tank filler neck that was on Big Blue says "FNF-027" on the side. And if you look that up it is for the later model tank/truck, as shown here on Amazon.

So, I already have one of the two filler necks that I need. So I called the salvage and explained that to them so they are only looking for the rear filler neck. But, I learned that they always cut the hoses, so I will have to replace them.

Which brings me to why BB was horribly slow to fill. In the pic below you see the filler neck that was on BB laying on the Bricknose tank on top, and the correct Bullnose filler neck laying on Big Blue's side tank on the bottom. Notice the size of the hoses protruding from the necks, with the Bricknose neck having a much bigger hose as that's where the gas goes and the air comes up around it. But the Bullnose hose is smaller and corrugated, and it is what the air goes through on a Bullnose.

Then if you look at the inlet on the tanks you'll see the problem. The Bullnose tank has a fitting into which the smaller vent hose is supposed to go. But that fitting is too big for the Bricknose hose to fit over, and too small for it to go into. I'm not sure how they had it in there, but however they had it there was some interference with fuel coming in and the air coming out, and that must be what caused it to be terribly slow to fill.

http://forum.garysgaragemahal.com/file/n69427/Bricknose_vs_Bullnose_Fuel_Tanks_%26_Pipes.jpg

Like they say. "A picture's worth a thousand words"

[kramttocs]

Like they say. "A picture's worth a thousand words"

Agreed. A helpful post

[85lebaront2]

The standard bed 1980-86 trucks can be a bit finicky, but the DRW models take the cake. The filler necks as the others have posted are a pain due to the design where the incoming fuel down the outer tube runs across the end of the inner (vent) tube. If due to age and possibly having a tank removed and reinstalled the inner hard plastic tube has broken, filling can become almost mission impossible.

In 1987, Ford reversed the design, so incoming fuel runs down the inner tube and the outer one is the vent, this greatly improves the filling process. The other change is in the tank venting, at the top of each tank is a roll over valve, which also incorporates a float to block any overfill from going into the evaporative system. Up to 1986 the line to the canisters is quite small, 1987 up use a 3/8" line and even in 1996 the over 8500 GVWR trucks still had an open to atmosphere small hose.

FWIW, here is a picture of Darth with the original bad removed so the length and some idea of the contortions of the filler necks can be seen:

Note that there is a short section where the cap goes then a long hose into the tanks, inside this is a hard plastic vent tube. I don't have any pictures of the inside. Also you can see the metal piece around the hoses, this is clamped to the bottom of the bed so the hose is essentially horizontal as it runs over the frame.