When I am going to be driving long drives yes, I can get an extral 200 km's on a tank filling it right up to the filler cap

 

The other benefit is that you can fill up w/ the 18 wheelers and their "bigger nozzles". You are full in no time - never trips off! Saves time on a long trip.

 

Sorry, but I have to coment on this, especially on "But diesel doesn't expand." Please don't anyone believe that. I see it every day up here in Canada. Even had a corporate safety bulletin come across my desk on exactly that topic today. Diesel does expand - quite a bit as a matter of fact. I work in the heavy equipment business, and one should never really fill a fuel tank over 80% otherwise you'll be calling an environmental cleanup crew later in the afternoon when the temperature has gone up. In degrees F, a 15 degree change in temperature is equal to a 6% increase in volume. That is significant. I haven't looked into "harpooning" a tank, but those hoses are usually there for venting of vapours. On new engines, these are actually routed to the intake manifold. Some will set a code if disconnected or the tank pressure is out of spec. I think I'll stick to filling up slowly.

 

^

I agree with the diesel expanding. Its not near as much as gas but it does a little. I'm pretty sure the vapor deal doesn't apply to diesel engines though. I don't even know where that thing goes or at least I can't trace it to anywhere in particular. And since the Diesel tank isn't pressurized it won't throw any codes.

 

Thanks Liv. Like I said, I haven't looked harpooning. I also don't know where the hoses on a diesel go. That said, that's another reason why I wouldn't do this mod. Basically to me it's about the safety aspect of the whole thing. Considering expansion of the fuel, you would probably get as much a benefit from filling up at night or in the cool of the morning than from this mod. Here in Canada fuel stations actually have to have volume/temperature correction devices on their pumps to compensate for different fuel temps. Consider this, at 50 F in the morning vs. 80 F in the afternoon, one could have a 12% difference in fuel volume. Not exact, considering the fuel temp. won't swing so much as air temperature, but significant. Especially in places where temps can vary a lot during the day. Are fuel pumps in the states equipped with correction devices?

 

The vent just goes up to the top of the filler neck, I only ever fill it right up either at night or if I'm going to be driving immediately, no filling it up to the the cap and then letting it sit in the sun. You do not get the same benefit from filling at night or in the cool of the morning, it takes just as long no matter what. When the vent is below the top of the fuel the air no longer has anywhere to go so the fuel starts foaming up and thats what cause the slow fills, allowing it to vent right up to the top of the tank just allows for that much more full throttle fueling. It really sucks when I'm out at -30 fueling it up for a long trip and I have to stand there for an extra 5-10 minutes just to get enough fuel in the truck

 

The volume of gasoline expands or contracts 1 percent with each 15-degree temperature change, The Los Angeles Times reported on a State of California-sponsored study that investigated the effect of temperature on retail gasoline.

WikiAnswers - How does temperature affect the density of diesel fuel

Density of Diesel changes with an increase in temperature, but I also believe it is less than gas. I will track down exactly how much.

Where I live (I know it is different in other locations, but just bear with me) we see a MAX of 30 degree temp swings in a day. In a week it is a max of 60 degrees. Most of the time these quick/large swings are drops in temperatures, not rises. Assuming a 60 degree change, you will see a 4% change in the liquid volume in gas (less in diesel).

Assuming you fill the tank up all the way to the fuel tank cap, even a slight liquid expansion could generate some very high pressures (liquids are essentially non-compressible) ..... that is ..... "if your fuel tank cap does not allow the expanded liquid fuel to leak out". I do not know for sure, but I would bet that the fuel tank caps are designed to allow liquid fuel to leak out before allowing pressures to get high enough to damage anything. That being said then, the issue becomes vapor emissions (or at worst - a little liquid fuel leaking out your fuel tank cap).

A 4% expansion of liquid in a full tank will be about 1.3 gallons. I am pretty sure that even with my harpooned tank, when the pump clicks off I can get another gallon in it. I will check on exactly how much tomorrow.

So a 1.3 gallon expansion acting on the smaller vapor space from a harpooned fuel tank will certainly generate more pressure than if the vapor space is larger (from the PV=nRT equation for the chemists and engineers). This just means that the vapor emissions from the fuel tank cap will initially increase slightly from a harpooned tank. That being said, in actuality the temperature increase acting on the vapor space itself AND changing the "partial pressure" property of the liquid will affect the fuel tank vapor space pressures ( and consequently the emissions) by 2-3 times more than that of the liquid expansion.

That being said, as long as you drive 20 miles pretty soon after filling up, then no matter how full you fill your tank you will be fine and any effect from the harpooning will be negligible. Even if you do not drive after a fill-up, just do not add any more after the pump clicks off the first time. As I said, you really won't be able to squeeze much more than 1 more gallon into it anyway.

 

FWIW - I found a source stating that diesel fuel changes 1% every 22 degrees (F) instead of the 15 degrees F that gasoline changes.

http://www.krausglobal.com/petroleum...mpensation.php

 

I'm pretty sure that it does expand. Ground temperature is in the neighborhood of 55*. Once that fuel warms up to ambient in the summer, it will have a tendency to expand some.

 

As referenced - diesel fuel expands and contracts 1% for every 22 degrees F change. What it does NOT do is "compress". You can not appreciably change the volume of a liquid through application of pressure. The expansion is NOT the 12% change in a 30 degree F temperature change (or 6% in 15 degrees F) that was mentioned previously. IMO - The worst case would be a spill of a gallon if it was filled all the way full AND the temperature increased 65 degrees F (for a 30 degree change the spillage would be 0.5 gallons). Any negative consequence to harpooning is extremely low probablility and even if you see some slight liquid spillage, it will be very small.

 

Let's not forget that Ford only make 2 tanks for F250/350.

That would be the big one and small one, doesn't mater if it's a gasser or diesel SAME tank.

SSOO anybody that can guarantee me a 50 to 100 mile increase between fill ups for FREE has got my attention!!


Been harpooned for 40K miles, not a drop on the ground yet.
ab

 

going back to the original poster, if you run it til 20 miles remaining there is a good chance that due to normal sloshing you will suck air. this reduces fuel pressure which is VERY BAD for the injectors. many times you won't hear a misfire or think there is a problem, but if it has an air pocket in the right spot when you shut it down, it will show a rough or hard start,"just like it ran out of fuel"

 

I like this especially since there is no cost besides time. Is there a link to removing the bed?

 

BPounds talks about it here -

Powerstroke Fuel Tank Modification

To begin, remove your tailgate because it will just be in your way getting into the bed, and it might cause interference with the bumper. On my longbed truck, there are 8 bed bolts. They are torxs style bolts. I removed the 6 forward bolts. The rearmost 2 bolts I backed out about 3/4", but did not remove them. These 2 bolts will serve as the hinge point for tilting the bed. I suggest you try loosening your bed bolts a day or two before you start this project to make sure they will come out. Bed bolts often are difficult to remove and a shot of penetrating lubricant on the threads a day in advance will help. If they just won't budge you may want to drop the tank instead. On the other hand, you could take this opportunity to cut the offending bolts out and replace them. Mine all came out without fuss. The bolts thread into captive nuts in the truck frame.

Once you have the bed bolts removed and the rear 2 loosened, disconnect the filler spout from the bed. Open the fill door, remove the fuel fill cap, and remove the 3 sheet metal screws. You cannot get to the 3 screws unless the plastic cap is off, so be careful not to drop the screws or your socket wrench down the fill opening. This will ruin your whole day. There is no need to remove the fill or vent hose from the spout. The spout will simply drop down.

You won't need to disconnect any electrical connections to the tail lights unless you are completely removing the bed. When ready to tilt the bed, use a suitable length of lumber on your floor jack pad up to a cross-member on the bottom of the bed. You should have some scrap lumber available to make lifting extenders and blocks as needed.