Fuel Tank Harpooning - More fuel, longer range

[SVO]

Ok this was brought to me today by an individual reading a diesel forum that I occasonally frequent.

Fuel Tank Hapooning = moving the vent tube of the fuel tank more towards the top of the tank as to not allow fuel to flow through it as soon (shutting off the filler hose from the gas pump), allowing you to put more fuel in the tank, rather than sit there and click the handle "X" number of times to fill the tank up as much as possible.

"Harpooning" means dropping the tank, taking a razor blade, and cutting off the vent protrusion. Then your tank should fill all the way the first time, each time.

Basically was wanting to know if anyone has tried this with successful results.

The diesel guys are saying that in there 38 gallon tanks normally they would only be able to fill thier tanks to about 32-24 gallons, after doing the "Harpoon" mod they are able to almost completely fill thier tanks all the way up before the gas pump clicks off, they spend less time trying to fill the tank by cicking the handle.






Jeff - :navajo:

 

[trucku]

wow thats kewl.

On my truck i can fill her up and she clicks right at the 21+ gallon (i drive her way into the E). On my 02 she clicks right at the top of tank specification of 22 gallons. I wonder how much more I could get in IF i tried to top her off like this.

I stop the fill at the click so my scanguage can stay calibrated properly.

 

[cybergasm]

This sounds like another one of those internet myths floating around. the one thing i don't see being covered is how much fuel is left in these tanks before there filled?? I doubt they diesel guys are gonna run their tanks bone dry before filling them and i know repriming a dry diesel system can be sometimes a major pita and it looks like when their gauges are showing empty that theirs actually 4-6 gals still left in the tank when they refill so they are filling to capacity but i guess they worrying about getting an extra half gallon or so in the fill neck? like this is gonna make a huge difference?. Dunno but this sounds kinda fishy to me.

 

[SVO]

http://www.forgotton.net/diesel/intank/index.htm









Jeff - :navajo:

 

[Stic-o]

This will be a problem for us California people. Smog laws are changing soon, and they will be testing your tank for holding presure

 

[sn0border88]

are we so busy that we cant wait the extra 20 seconds to top off our tanks?

 

[Bill Kemp]

YES! Time is money. Thats my 2 Cents worth.

 

[section525]

I use to drive a lot, stopping to fill the tank mulitple times in one day. I can see how these guys will do what it takes to get that extra few miles between stops.

I got it to where I could go nearly 800 miles between stops. That's about 7 states for you East Coasters.

 

[gijoecam]

The air gap at the top of the tank is designed to allow the fuel to expand and contract without forcint it to purge raw fuel out the evaporative emissions system. To defeat that is asking for trouble IMHO.

On a 2nd-gen Explorer, IIRC, the filler neck and vent tube come in through the end of the tank, angling downwards only slightly at the end. Furthermore, there is no plastic piece on the end of it; it's steel. (I worked on the line that made the tanks for 6 months or so, but that was a decade ago)

-Joe

 

[Mr_Evil]

This works for Diesels because we don't have evaporative emissions systems (at least my 2000 F250 doesn't) and Diesel fuel doesn't expand and contract as much as gasoline.

 

[gijoecam]

http://www.chevron.com/products/prodserv/fuels/bulletin/diesel/L2_4_6_rf.htm

A typical value of the coefficient of thermal expansion for diesel fuel is 0.00046 per degree Fahrenheit. Using this value, 1.000 gallon of diesel fuel at 20°F will expand to 1.037 gal-lons at 100°F.

http://reviews.ebay.com/Myths-about...0001229830?ssPageName=BUYGD:CAT:-1:LISTINGS:1

the coefficient of expansion of gasoline is 0.00060 per degree Farenheit.

Diesel expands about 1/4 less than gasoline... but you're also dealing with a much larger volume of diesel fuel than in an Explorer, so the actual volume change in a 40 gallon diesel tank will be significantly more than in a 16 gallon gasoline tank. However, it's a moot point.

And not to burst your bubble, but even the diesels have an evaporative emissions system.

-Joe

 

[Charlie]

I can't top off mine, mine fills all the way, every time. I have tried a few times to top off, but every time it spills, and makes me mad.

So I don't bother trying anymore.

 

[Ford_Forgotton]

And not to burst your bubble, but even the diesels have an evaporative emissions system.

-Joe

Dont know what Diesel you refer to, but on my 2000 powerstroke, there is no evap system. The superduty (99+) uses the same tank for gasoline as diesel, but the diesel tank vents are just tied directly to each other instead of to a charcoal can. There is no charcoal can on my truck. Nor is there any form of vent tube going into the intake to burn the evap gases. Only the crankcase vent goes into my intake, and all that is good for is coating my intercooler hoses with oil.

The Harpoon mod on my powerstroke enables me to fill all the way to my fuel cap. If you were to do this on a gasoline truck, you would probably flood your evap system.

I could still fill to the cap WITHOUT the harpoon mod, but it took FOREVER! Diesel fuel likes to foam up when agitated, such as when filling, and that foam triggers the shutoff mechanism on the fuel pumps. The harpoon mod allowed me to get the tank almost full before the dreaded click off occurs.

Ford lists my tank as a 29 gallon tank (shortbed), but I have gotten 31.5 gallons in it. Yeah, it was empty, as my fuel pressure gauge was going nuts from the air in the system. Not something I try to do often.

Oh, and while I wouldnt recommend it, you can run the powerstrokes out of fuel. The 94-97 trucks you'll need to manually refill the fuel bowl as they have a mechanical fuel pump, but the 99+ trucks have an electric fuel pump, and you just need to cycle the key a couple times before starting. The powerstroke injector is designed to purge air out the tips. Again, not highly recommended, but doable.

For a bit of history, the term "harpoon mod" comes from TheDieselStop.com, back when it was still called Ford-Diesel.com. A user there named "Maroon Harpoon" found that trick to cutting the vent tubes, and the mod was named in his honor.

Anywayz. Harpoon mod on diesel superduty =
Harpoon mod on gasoline exploder = :thumbdwn:

I did see an exploder a month or so ago running around Portland, OR that had been converted to Diesel. It was on the freeway, so couldnt stop the guy, but wish I knew what he put in it! He had stickers all over it to make sure everyone knew it was a diesel tho.

 

[96XLTRanger]

i cant pull the trigger all the way or else the filler overflows and i get gas on the ground, even when my tank is empty.

 

[Joe Dirt]

I usually go two clicks then up to the next full dollar, so I can get a somewhat consistent fill to base my mileage off of. I filled it once so well apparently- I drove 160 miles before it even started to drop below over-full. Gas was cheap that day...

Is there anything that bugs you more than having gas overfill and run down the side of your truck? (or on the ground throught the filler drain...) Man I hate that!