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Thread: Auxiliary Fuel Tank & "Spare fuel" questions

  1. #1
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    Capt. Mike, Checking out your aux fuel tank pic's on your web site. I can see that the tank is located under the sliding door. Do you use the main fill tube and then tee in a line to the new tank? I'm thinking of doing the same to my 83 1/2. mike m.
    Last edited by Capt. Mike; 05-27-2008 at 06:55 PM.

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  3. #2
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    Well, it appears my original topic on auxiliary fuel tanks has disappeared. Probably a casualty of Infopoop's last update that screwed up so many boards.

    First, my auxiliary fuel tank is in a Syncro. That means my main tank is in the rear and has a rear fill. Thus I was able to put in a new fill in the position used by the regular 2WD models. the sheet metal is even indented for it.

    My fill goes from the new filler through the wheel well and connects to a steel pipe through the cross frame. This was chosen so as NOT to have the fill line go below the protection of the frame and have a low spot. However running through the frame mean a large hole with the potential to weaken the frame. Thus we drilled an 'exact fit' hole for the pipe, ran the pipe through and then welded the pipe into position to restore any lost strength. A 2nd section of hose then runs to the tank fill neck. The hose in the wheel-well is very heavy duty, wire reinforced to withstand thrown up rocks, etc.

    The fill is a marine through-the-deck filler for small boats. Mine is a Perko brand with covered key lock. Since it does NOT have the fill pipe venting of a VW OE, venting is through the aux. tank's expansion tank and charcoal filter systems. Fill is a lot slower but this tank is only used as auxiliary, not to expand the capacity of the system in normal use.

    Examine your goals. I wanted auxliary fuel not just as emergency run-out, but to manage fuel stops (avoid the rip-off of little remote stations) AND to provide the fuel for my dual-fuel Coleman stove & lantern. I even keep 5 gal. in it as reserve around the house for my generator in case of power failure. Thus I wanted a slow pump and a quick-connect discharge so I can pump via hose to either my main tank or to someone else & equipment. This requires planning and understanding of the pump capacity and non-vehicle use.

    When used for the vehicle, I basically transfer the whole tank and pump dry. This gives me a known state for the next fill. You'd be surprised how much fuel you use in the Colemans camping. I once, not needing aux. fuel, camped for an extended period and found, when I did finally transfer the remainder, I was down to about 2-3 gallons out of the original 7. Now I routinely transfer the contents during camping trips so I'm typically refreshing at about 5 gallons.

    My pump (Facette 3psi) is deliberately slow -- about 3 minutes per gallon. This gives me a pretty good guestimate on what I've put in the tank and reduces overflow spills. Chose a pump specifically for that, not a new-car fuel pump -- they will be too fast.

    All fuel has a shelf life. I routinely use a stabilizer/preservative in every aux. tank full (except in the middle of a camping trip where I'm pumping out every few days). Even around home I transfer about every 3 months. I use a Motorcraft P/N FG14C filter in my discharge to pump line.

    Back to your original question. You can still put a front fill in the 2WD versions. There appears to be room to put a small second fill just below the OEM and the little deco indent, but you might also consider a steel neck filler in the manner of many dual-tank pick-up trucks since the higher (greater drop) the better. This could be a filler neck inside the wheel well clear of the tire range of movement. Obviously less convenient to fill, but doable. You'd have to bracket & brace the neck into position and install a cap that is very weatherproof.

    The type of underfloor aux. tank I have is not without problems. It is long and flat (1090x260x105 mm). Liquids don't like that, and compounded by my desire to vent EPA style, means my fills are slow. The slowest notch on the nozzle at best and hand top-off at the end. Since the fill enters the tank RF, I need to have the vehicle LR a little lower so it fills completely. Thus I pick the gas station island carefully and may even park at an angle. The opposite is true on pump-out. There my fitting is RR so that needs to be the lowest point. I try to park on that angle and slope for maximum empty.

    Any tank that long must have baffles. Carry a flat pan of water at a run and you'll see what I mean. Without, the freesurface effect (sloshing) of 7 gallons -- over 40# -- can damage the tank, its connections or strain the mounting during the more violent vehicle movement (which happens too often where I camp!). My tank has baffles dividing it into 3 sections; this means the drain holes in the baffle restrict fill. It's not so noticeable during pump out due to the slow pump. But I will get another pint or so if I let it drain after the first pump-out. Again, slope affects how quickly it will run to the rear.

    I sit here looking back on my plans and materials list and am still amazed that we did it! But I had the help and advice of a master race-car fabricator who mades it all look easy! This one is .090 aluminum which is easy to fabricate and relatively inexpensive but my next will be stainless steel. Aluminum requires extensive anti-corrossion coating due to winter salt and calcium chloride road treatments in the far NW. We did line the inside of the tank with one of the liquid liners. I suppose galvanized or aluminized stock would suffice in some areas.
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    Last edited by Capt. Mike; 01-23-2009 at 07:24 AM.

  4. #3
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    On our Type II Bay Window '79 Westy, for our AK & NW Canada trips, we carried an extended bumper with racks for either 2 x 5-gal. jerry cans or one can & a small generator. Simple to make -- U-channel stock drilled & tapped for original mount hardware; plate welded to end to mount wood bumper face on; small lip on end plates for mounting lights. Bumper made of 2" x 6" wood and tray between body & bumper made of 1" stock. Brackets for cans mounted to tray; bungee tie-downs for when carrying generator. The gas can bracket on the generator side could be removed with just 2 nuts.

    It worked very well, though one had to remove the cans to check engine oil. I made it such that the entire bumper -- on its own brackets -- would just slide into the frame and bolt, much like the original bumper. I could then swap back for normal use. Each bumper had the auxiliary light brackets so swapping bumpers didn't cause problems for the lights -- they just need a little extra wire to reach the added length which was wire-tied out of the way when on the short bumper.

    There was additional weight, but I'd guess <100 lb., counting the gas. Since I removed the steel bumper and, when camping, I moving the spare to the front of the vehicle, it seemed to balance so there wasn't any drop to the rear of the vehicle. Headlights remained aligned. [Hint: notice the silver reflectors on the cans? They are USCG marine rescue reflectors (for life vests & rafts) and extremely bright. They help keep tailgaters back.]
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    Last edited by Capt. Mike; 11-11-2009 at 03:15 PM. Reason: Update

  5. #4
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    I think this is one of those cases where the cure is worse than the disease. To have a venting that is spill-proof, it would have to be piped to an expansion tank or chamber. One should then vent the vapors in a safe &/or EPA approved manner (to the charcoal cannister). Most of the venting systems I could find are either large or too complex to add to a gas can. I did find Arrow Thrust makes a vent check valve for " hose. You could mount it somewhere that pipes into the charcoal filter system, install a " nipple on your can and just connect/disconnect the hose when you remove the can. This only vents excess pressure -- it does not prevent overflows.

    All of the DoT approved cans I found are strengthened and 'spill proof' and infer they can handle the expansion. The round ones with the spring pressure caps, would theoretically vent when the internal pressure reached the equivilent of your hand strength to open them, but they are lousy shapes for carrying as a strap-on. I prefure the tried & true real GI gas can. Blitz sold their Model #11010 as:
    Rugged, corrosion-resistant heavy-gauge steel Polyethylene screw-on cap. Dome top design for fuel expansion with vent. Perfect for automotive, recreational, marine, farm, and ranch usage. Made in USA, Weight: 8.94 lbs., Manufacturer: Blitz
    Mine has a 1/8" vent hole at the 12 o';clock positing in filler flange. Since it is covered by gasket when the cap is on, I presume it's really meant as the vent for pouring when the nozzle is on as that gasket does not cover the vent. Blitz has discontinued that model for the #81733 with Enviro-Flo. That appears to be a spill-proof vented pouring apparatus. They can appears the same . It was built to conform to California EPA.

    You will find that your can (if a quality unit) has a maximum fill line that leaves sufficient space for reasonable expansion, although it will still have pressure that must be released carefully before using the can to fill anything. Blitz cans are rated at an expansion pressure of 20 psi.

    The coefficient of expansion of gasoline is 0.000528/F. Assume an underground station tank's fuel at 55F that heats to 120F in the sun. The expansion of 5 gallons would thus be .03432 gallons or 4.4 oz. Most commercial quality steel cans -- the true DoT approved -- will have at least this much expansion room and still handle the pressure. If in doubt, leave your can's fill short by an additional pint. Also, if you release your pressure in the heat of the first day, subsequent contraction & expansion should leave you spill-free.

    My built-in auxiliary fuel tank has both an expansion chamber with overflow and a vapor vent system to the vehicle's EPA charcoal cannister.
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    Last edited by Capt. Mike; 01-23-2009 at 09:11 AM. Reason: Update

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