danalex

Hi. I'm going to set up an aux tank for gravity feeding. ((sorry if I don't use the correct technical names that follow))
I'm laying on my back looking up from underneath the truck, looking at the fuel fill pipe. Got it; the large fill tube feeds directly into the tank...it is aluminum-like and then joins into a larger rubber hose section which goes into the tank. Also up near the mouth of the fill tube there's a smaller fill pipe/tube running along the side of the large tube (I'm thinking this must be for "overfill run-off", but not sure). The upper portion of the small tube is also like aluminum, but eventually it feeds into a rubber hose which runs to the "top plate" structure screwed onto the top of the tank. Coming from that plate structure is a fuel line hose which runs to my Raptor fuel pump.
Ok, now the questions:
1) Which tube should I "T" into, the large or small?
2) Should I "T" into the hose portion of the line or the aluminum pipe? (I'm alergic to explosions...)
3) There's sufficient fuel line hose running to the Raptor pump; should I "T" into that hose? This would take a longer length of hose coming from the aux tank, but that's doable...just not sure if it's recommended.
4) My tank is a small 50 gal; thin enough to fit between the tirewell in the bed (short-bed truck). I'm thinking about an inline filter, but I'm not sold on the idea. I could get one from Tractor Supply, and can find a bed rail someplace underneath to mount it...seems like extra work. I can also get a typical "in line" filter like for a regular gasolene (just pick off the shelf at autozone). The extra inline filter set-up seems overkill since the stock filter up in the engine block area seems sufficient....undecided...cost + hassle are factors.
5) The aux tank is from craigslist; it already has ball valve switch.

Any advise?

Lt.B

The factory tank is not sealed, the cap is vented and a 50 gal tank mounted in such a way will overfill the factory tank (34 gal) and you will have one big mess. Use a 3 way valve and tap the line feeding the raptor. The valve will cutoff the tank not being used. Your regular filter should do all the filtering you need.

danalex

HHmmm....cap is vented, huh? I hadn't figured that... I was really hoping to just have the aux tank feed into the main tank.

OldDodgeOwner

I ran mine into the vent on top of the tank. Looking at the top of the tank, where the Raptor ties in to, there's a 3/8" barbed fitting with a rubber cap. I ran the hose to that. This will allow it to overfill though.

I set mine up with a manual ball valve on the tank as well as a 12 volt solenoid valve inline. The solenoid valve is tied into the ignition, a toggle switch, and an LED in the dash. The valve will only open with the ignition on, closes when you turn the key off. While running, I can open it with the toggle switch, with the LED as a reminder it's on. I generally open it until it gets to about 3/4 of a tank, then shut it off.

Lt.B

ODO has a pretty good arrangement. There are lots of ways to do it you just have to find one thats right for you. If your tank wasnt vented it would collapse from the negative pressure. I saw that happen once on a little Isuzu Pup. The owner had put a non vented cap and it didnt take but one tank of fuel. Diesel is not as volatile as gas and doesnt evaporate as badly. I had a similar setup on my boat for when I went offshore and wanted a little insurance. I carried an extra 25 gal in an on deck tank and ran that out first and then switched over to the 160 gal below deck tank, disconnected the on deck and stowed up on the hardtop. that cleared the deck for fishing. I used a 3way valve and a quick disconnect and never had to slow down to change over. When I fish local of course I dont have to carry the extra tank. It is plastic lightweight and stores anywhere. I had to vent that tank as well because the outboards consume alot of fuel in a big hurry. On a boat we talk gal per hour instead of miles per gal.

nickg

the fuel caps have a vacuum and pressure valve, vacuum valve is designed to maintain a certain vacuum valve, this aids in removing air from the fuel due to sloshing and filling, most times the valve sticks in the cap causing issues, every thing from hard starts to collapsed tanks.
I had a GMC diesel that I "T" into the smaller line next to the filler neck, and my aux tank in the bed had a manual shut off valve, I drove clear across Canada (5000kms) it never overfilled once!, that being said there are some things to be aware of.
1) you need a properly working fuel cap.
2) shut off the ball valve when not in use
3) shut off ball valve if fuel cap is removed, should you be filling the main tank, or it will overflow
4) The lower tank will stay at what ever level it was before you opened the ball valve, and it will stay at that level until the upper fuel tank's fuel is burned off, THEN the truck tanks level will start dropping(as seen on the fuel gauge)
4a) your aux fuel tank needs a proper valved fuel cap (just like the truck fuel cap) If it does not allow air in, it will not allow the lower tank to fill
5)This set up is not legal (automotively speaking, because it is a gravity feed), so should you have an accedient or be pulled over, you might have some explaining to do. filling your tank when stopped would work as well, ie open your truck tank fuel cap, then open the ball valve, and wait while the upper tank fills the lower tank, then close the ball valve, this will be slow because of the size of the fuel line.
Or hook it up as mentioned above so that your fuel pump sucks from the tank (harder to do but in the long run safer)

johnh

that's the way i have mine, but i have a electric pump to speed up the transfer, effectively stopping gravity flow..
(not planned ) mine won't over fill unless i forget to turn off the pump............

marathon

Northern Tool has a kit for the fuel line for $70. It includes a ball valve that will cut off the flow once the fuel level in the fuel tank reaches it. Make sure to teflon tape the joints or they may seep. Diesel has a flash point way higher than gas, so I just used a razor blade to cut out a section of the hose and installed it.

Works fine for me.

danalex

Yeah, I noticed the Northern Tools kit...so does the long hose go down the fill tube into the tank? If not, how does it prevent overflow...especially if I have a 50 gal tank feeding it? (wish the ad on N.tools had a .pdf instructions sheet). thanks

infidel

Be careful how you deal with the return fuel. If it isn't going to the tank you're drawing from an overflow is possible.
Common mistake.

marathon

The Northern kit comes with a manual valve for the bottom of the aux tank. Attach the small hose to it. Cut a hole in the bed nearby and route the small hose through it. Find a place that's relatively flat and take about 1.5 inches out of the filler hose. Put the large pipe inbetween the cuts with the valve upright. Cut some of the extra length out of the small hose and attach to the top of the check valve.

There is a diagram on the kit. All the parts and clamps are included except for the teflon tape which I would recommend for all the metal fittings.

Most of the time I just fill the aux tank and go.

danalex

Thanks marathon; I think I'll do it that way. So, you typically fill-up the aux tank. I presume you do that when your fuel gauge indicates a certain level (perhaps 1/4 tank). This, I assume, in turn causes your stock tank to fill gradually... And you don't have any "overfill" overflow issues? Come to think of it, this method sounds alot like my original post/intent to put in a T-intersection...the kit (with a built in tap) just sounds like a "cleaner" organized way to do...

marathon

I like the effect the extra weight the full aux tank has on my ride quality, so I look for about 500 miles on the trip meter and refill the aux tank. My fuel gauge doesn't move from full.

On long trips I'll refill when I want, or when I know it's cheaper, starting with the regular tank and then the aux tank. No overflow problems and there is always a void at the top of the regular tank because the valve cuts flow off before it gets to the fill cap.

rebal

I tied into the top of the tank theres is a fitting with a rubber cap . I also used a electric solinoid valve to shut off the fuel so as to not get an overflow
sitchyation

danalex

Great! I picked up the kit yesteday; plan to install this weekend. The instructions say to mount the hose adaptor-thing as horizontal as possible with the "valve" upright. Crawled under the truck and notice the main fill hose is relatively flat nearer to stock tank (further away from the top/fuel cap). So, I should be able to manage to position the adaptor-thing per instructions (aprx 1 foot away from the stock tank).
Now, about a "vent"...do I need a vent valve? The aux tank only has one "drain" hole (no additional vent valve). I'm assuming the aux tank fuel cap (with pressure spring) should provide suffient "venting". Additionally, the regular fuel cap should allow venting too. There are a couple of "nubs" on the stock tank, but I don't know which (if any) of these are "vent" nubs. Do I need to be concerned?