Auxilliary/Transfer Fuel Tank

[PLevesque]

I have been giving some thought to installing an in-bed auxilliary/trasfer fuel tank to increase towing range as well as to service equipment. I have seen the RDS tanks at Northern Tool and wondered if any of you have installed one on a 2007. 5 using a gravity feed to the OE fill tube and how good it works. Thanks in advance for the input.

 

[MMeier]

FYI, gravity feed is illegal.

 

[PLevesque]

The install kit Northern sells ($69. 99) is said to automatically control flow to prevent overfilling and also has a shut-off valve. I want to be legal as well as safe. This system is not legal? If not, how can they sell it and what is a legal alternative? I need to know for sure before I buy.

 

[Sled Dog]

I have been giving some thought to installing an in-bed auxilliary/trasfer fuel tank to increase towing range as well as to service equipment. I have seen the RDS tanks at Northern Tool and wondered if any of you have installed one on a 2007. 5 using a gravity feed to the OE fill tube and how good it works. Thanks in advance for the input.

It works Great. And allows me to shop for the best diesel price rather than being bent somewhere on the interstate. But with an extra 150 gal. capacity you better have 6 or 7 C-notes in your pocket for fill-up.

 

[GAmes]

FYI, gravity feed is illegal.

That is an internet myth that was started by taking the federal regs out of context. I believe Transfer Flow started it. The reg reads that it is illegal to have gravity feed to the injectors. I'm not sure how that could be accomplished, but that is what it says.



393. 65

 

[boatpuller]

It works Great. And allows me to shop for the best diesel price rather than being bent somewhere on the interstate. But with an extra 150 gal. capacity you better have 6 or 7 C-notes in your pocket for fill-up.

I just got a tank and am trying to decide if I want a pump or to just go with the gravity system, on the gravity system I am just worried about having fuel up against the factory fill cap. Do you know if there is fuel backed up against the factory fill cap or does the fuel ony go up to the level of the fill line where you place the fitting from Northern. I like the idea of the gravity feed much better(keep it simple) than having a pump. I did decide to just put a momentary type switch on a pump so that it wouldn't get left on accidentally.

Thanks for any info you can give me on if there is fuel up against the factory fill cap.

 

[Sled Dog]

I just got a tank and am trying to decide if I want a pump or to just go with the gravity system, on the gravity system I am just worried about having fuel up against the factory fill cap. Do you know if there is fuel backed up against the factory fill cap or does the fuel ony go up to the level of the fill line where you place the fitting from Northern. I like the idea of the gravity feed much better(keep it simple) than having a pump. I did decide to just put a momentary type switch on a pump so that it wouldn't get left on accidentally.

Thanks for any info you can give me on if there is fuel up against the factory fill cap.

If it fills behind the factory cap don't worry, It Does NOT Leak. Personal experience. If you install the float/ball valve plumb, I don't know, but I don't believe it will fill up much past the valve, to the cap.

 

[CKelley1]

we found you can gravity feed through a 2 micron filter and it works perfect have made my own and used northern's the filter is carquest 86377 $9 and the base was a napa 4309 i had to change the center , the filter has 7/8-14 threads we read the law and what it says it is illegal to feed the motor from the aux tank but ok to feed the stock tank from the aux , confirmed with dot

 

[MountainMan1]

Beware of aux tank size... I have heard many times that if you exceed a 119 gallon tank you are considered to be distributing. You'll then need to be commerical and also need hazmat placards! One hundred fifteen gallons is the common largest sold by aftermarket dealers by my experience.



There is also a 60 gallon oem replacement but in combination with the 115 you'd be illegal.



Now as I think about it I read that I my company info board, we're RV haulers, and it is a rather complex piece to read. I just know that I am legal with the 115 gallon aux.

 

[jelag]

A couple of thoughts... most semi's have several tanks and they gravity feed to one another... I have a second tank on my 5500 and it gravity feeds to the main tank... . its a 80 gal tank and functions well... . and has just gone trough its first DOT safety check with flying colors... 80 gal aux tank and 52 gal main tank... photos of the 5500 with its aux tank were posted on the TDR...

All my 3500's have a 120 gal tank in the bed... we have a 1/2 lb back check valve to keep it from over flowing the main tank as its plumbed into the main tank... we turn on a pump, and run it for 15 min and pump the main tank full... no one has ever asked the size... . no one has ever measured them... . they have been dipped for dyed diesel more times than I can count and once, one of the trucks was inspected at the border to make sure it didn't have an empty cavity to hold anything... . they are the size they are because of the space available and we didn't want a tank that was over the top edge of the bed.....

Between the main tank to the engine is a 10 micron main filter, a 2 micron secondary filter and than the factory filter on the engine... The aux tanks in the bed are custom made in our shop... again these trucks have DOT numbers and have been through a lot of inspections... with no problems... .

The installations are clean, safe, and professionally done... . we just traded a 2000 F550 with the same set up with 500K miles, our 04 3500 has 250K miles...

Each installation is different..... each has it own merits or downfalls, we just wanted something that worked and was inexpensive and would last the life of the truck... . all our 3500's have the same set up... but our other trucks are unique because of the issues we faced when we did the install...

 

[KnightR]

I have a 76 gal. TRANSFERFLOW aux. Can't seem to see any fuel filter other than the factory. Like the idea of pumping from aux. to main, and the extra fuel filters. What kind of project do you think it would be on my 98 3500 dually?

 

[CKelley1]

we have installed several of the 105 gallon L tanks and 2 micron filters, gravity feed. my shop is a little better than some but only took about 4 hours to mount tank, filter and fittings even added a fuel gauge to the L tank

 

[steved]

I would research that fuel neck deal from Northern prior to buying... I remember a thread about it being too restrictive and the gravity feed not being able to keep up with demand.



I run an auxiliary in my toolbox, force feeding the main tank with 3/8" lines through a 10 micron filter... works well.



FWIW, I have yet to plug a filter that is half the size of a OE filter (I use an FS1251)... so our fuel must be somewhat clean. I have ran this tank 45k, only replaced the filter once (only because I have a dozen filters sitting there!).

 

[wheatman]

I have a Northern Tool Auxillary/tool box. Set it up for gravity flow and it works with no problemo... no leaks... so simple its amazing. There is a valve so you can manually shut off the tank at the tank. There is a breather nipple just under the fuel cap, i attached about 2ft of fuel line with an inline gas type of fuel filter on the end to keep the junk out and allow tank to breath (may not even really need this but made sense to me). I run down my main tank then flip open the valve to start the transfer.



There are connections on the tank to really properly hook up an inline fuel pump and to accomodate a return line if you needed. Eventually when i get a bored day off I will mount a pump under the frame along with a filter, guess gravity flow would work with a filter but there really isn't much of a drop from tank to the filler hose connection.



In the end I took a chance with the NT but it was so many more $'s in my pocket than the TF that i had to try it. One of the best mods i've done.

 

[Sled Dog]

I would research that fuel neck deal from Northern prior to buying... I remember a thread about it being too restrictive and the gravity feed not being able to keep up with demand.



I run an auxiliary in my toolbox, force feeding the main tank with 3/8" lines through a 10 micron filter... works well.



FWIW, I have yet to plug a filter that is half the size of a OE filter (I use an FS1251)... so our fuel must be somewhat clean. I have ran this tank 45k, only replaced the filter once (only because I have a dozen filters sitting there!).

Northern kit( fuel neck-gravity flow)=No Problem Keeping Up. Alone or pulling Heavy, OEM tank stays Full until reserve is empty, then needle starts to drop. You may think it fills the OEM slowly, But its faster than the Cummins can take it out. Three years now with it and No Problem.

Gravity flow makes so much sense, compaired to the cost of pumping down hill. JMHO

 

[steved]

Three years now with it and No Problem.



Gravity flow makes so much sense, compaired to the cost of pumping down hill. JMHO

This was a recent thread... maybe the design changed? I know it is on this forum, and the owner removed the guts of the thing in order to make it work... IIRC, they stated it was smaller than a 1/8" hole and it wouldn't keep up.



There is some advantage to having a pump:



First, I can run my auxiliary dry, pull into a station, and force feed the main tank while filling the auxiliary... when I leave the station I have two completely full tanks, and very little wait time filling the main tank through the auxiliary (I prefilter all my fuel using the auxiliary tank).



Secondly, filters between the auxiliary and main can be used longer since you can actually pump through them with a little pressure.



There are advantages to both setups... I like mine because I can gravity feed through the pump (vane-style pump) and still have the advantage of a pump when needed...

 

[Okie-Go]

I have a 66 gallon aux tank in the bed also. I have a small pump mounted on the frame to transfer fuel from it to the oem tank. There is a filter between the two. It is controlled by a switch in the cab. The only bad thing with mine is to not let it overfill. Some folks I have heard have a light on the switch to remind them it is pumping. I have my tank and pump on the third truck now.

 

[steved]

The only bad thing with mine is to not let it overfill.

Agreed... I have accidentally bumped the switch before. Mine is lighted and has a standalone light... it wasn't enough!



It will start forcing the fuel out the rollover valves on top of the tank.



I've found I just need to get the setup primed, it will gravity feed on its own unless it loses the siphon (mine is a top draw).

 

[Sled Dog]

Agreed... I have accidentally bumped the switch before. Mine is lighted and has a standalone light... it wasn't enough!



It will start forcing the fuel out the rollover valves on top of the tank.



I've found I just need to get the setup primed, it will gravity feed on its own unless it loses the siphon (mine is a top draw).

My tank in the bed drains from the bottom to OEM, no siphon required

If aux tank is empty and OEM is low, I fill with the big trucks, both tanks at the same time.

 

[Joe G.]

I had a small problem with gravity feed. The pressure relief valve on the fuel tank module would leak a little bit if the main tank was full and the aux tank had plenty of fuel. The aux tank feeds from the top. I changed the system. I installed a tank selection valve on the frame rail in front of the firewall. When the aux tank is selected the stock lift pump draws from there. Return regardless of which tank in input is to the main tank. This setup really moves fuel!! The stock lift pump on a 12 valve is rated at about 55 GPH so most of the fuel it pumps goes into the return line. I don't know if this will work on any truck with an electrical lift pump.