Auxiliary Fuel Tank

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I bought a fuel tank the other day from an RV sales place here thats going out-of-business. It came out of a diesel powered motor home, fits perfectly under my across the bed toolbox, and holds 36 gallons. My plan is to gravity feed this tank into a T in the main tank fuel filler tube and to also T the vent line and run it back up to the vent in the fuel filler neck of the aux tank. Have any of you done something like this? Iwould appreciate feedback, hints, possible problems,etc.
Thanks,
Russ

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99 3500 4X4 Quad 5-speed 3. 54LS White/Agate 235/85 Michelins, Rancho RS9000s, Reese 15K 5er Hitch, Stainless Bedcaps and Wheelwell trim, Mopar Dually flaps with Geno's Chrome tips, Geno's Monster Exhaust Tip, Scotty style K&N, Bosch 275 HP Injectors. Purchased 16June99, 1OK Miles so far. Average MPG: 17 City 20 Highway

 

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I did something similar. my truck is a flatbed with a 50 gal aux. tank hanging under the bed. I use an electric fuel pump to tranfer the fuel thru a "T" plumbed into the vent line by the filler neck. Have not had any negative experience doing it this way. At the time this was hooked up I could not find a "T" to fit the filler neck so used the vent line thinking it be a temp hookup as I was loaded to go Ma. and was pressed for time. As to the vent on the auxiliary tank I attached a plastic inline fuel filter with a small piece fuel line to the vent port on the aux. tank. It worked so good on that trip from TX. to MA. and back I never changed the hook up. I've been runnin this setup for atleast 180,000 miles. I do believe it would be better to "T" into the filler tube though as you described.
We hooked a friends Ford up with a gravity feed setup into the filler neck and used the fuel filter attached the vent port, it works great.
good luck

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97 cab/chassis 1 ton,11'flatbed, bd injectors, K&N filter,Cobra 29 CB, pulling 40' flatbed g/n,vac/hyd brakes
200,000 miles and counting

 

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If you want to T into the fuel filler here are a few points of interest: There is a green plastic ball in a white nylon (?) cage at the end of the filler tube. It is an anti-fuel drainback in case the truck rolls over. It also restricts fuel flow enough that you have a problem at big rig fuel pumps.

The older Dodge Ramchargers used a steel pipe of 1/2" diameter between the fuel filler and the tank. The pickups and the Ramchargers used a steel 1/2" vent tube at the side of the fuel filler tube. You can cut off the last 2" of one of these tubes and have a nice end which is bulged to retain a hose.

These parts are easily available at the junkyards. I like the screw cap fuel inlet used from 1981-up for auxiliary fuel tanks so both it and the standard Ram tank can use like-keyed locking fuel caps. You can solder the last few inches of such an inlet to 1. 5" pipe and adapt it to the pipe thread inlet of an aftermarket fuel transfer tank.

Drill about a 7/16" hole in the side of the Ram's fuel filler tube near the bottom of the vertical travel part. You can position this hole and the stub of tubing so it lays horizontal and against the Ram's vent line. Find a 1/2" diameter bolt, heat the filler tube (after rinsing the fuel out), and drive the bolt into the undersized hole. This creates a concave area around a hole that is now large enough for the stub. Clean off any paint and solder (former on the Ram's inlet, latter on the vent stub). Silver solder the stub into the filler tube, filling up the concave area. Silver solder the stub onto the Ram's vent line for added strength. I would use home air conditioning grade silver solder as it is strong, but it will require an oxyacetylene flame to melt it properly. Because of the heating, you will burn the black paint off the Ram fuel filler, and if the green ball and nylon cage are left in, they may melt... Be sure to use a wire brush to remove any damaged paint from the inside of the Ram's filler tube.

With such an inlet arrangement, you would have plenty of room under the bed, outboard of the frame rail and forward of the fuel filler, to install a bulk tank filter such as Cummins #33074549 (takes Fletguard FF246 cartridge), and perhaps even Fleetguard FF5079 screen filters as prefilters if rust is a problem. One way to to this is dual screen filters in parallel (they have 5/16" hose connections) and then 1/2" hose to the bulk tank filter.

Hope this helps.

 

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We have added axillary tanks to several trucks now. In all cases we "T" into the vent line with no return line. We add a silinoid valve (1 in, 2 out valve from older Chevy right left tank) inline to allow control on the go from the cab. Using gravity you CANNOT over fill the main tank it you forget to shut the valve off.

It drains slow but on several heavy pulls getting 8 MPG I was able to keep the gauge from dropping.

We add no filters as the main system has a good filter design. BUT, we designed the intake inside the tank using a 90 elbow point down within a 1/4 of the bottom of the tank to deliberiatly suck every drop out.

I have passed over 10,000 gallons trough my tank in the two trucks I have had it in. This system also works well in cold weather and #2 fuels.

BTW these tanks are homemade 1/8" STEEL treadplate. No rust issues if you keep them full.

jjw
ND

 

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I added 90 gallon motorhome tank to my '97.

The tank has a sending unit and fuel pump built-in, so I put an extra gauge under my dash, and a switch to activate the pump.

I cut the truck tank vent hose, and connected the new tank to pump into the vent connection at the top of the filler tube (near the cap), and connected the truck tank vent line to the aux tank filler neck.

Now, I never loosen the truck cap. I always fill thru the aux tank. (unless you run them both dry)

If I forget to turn off the aux pump, while going down the road, it fills the main tank, then just pumps it up the vent line and back into the aux tank. (as long as that truck CAP is tight) No problemo!

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4-Rams

 

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Russ;

The Correct way to do it is with a motor selector valve to switch between the two tanks. It can switch both the feed and return of both tanks. Thus no chance of over filling the main tank. This requires the main feed and return to be cut and the selector valve spliced in there. Install a inline fuel filter on aux. feed at tank. this will get filtered again through the main fuel filter. A toggle switch in the cab Will switch between the two tanks. A fuel gague can be put under the dash for the auxiliary tank.

I have two 40 gal. aux. saddle tanks instaled in my truck with no problems.


Y2K,2500, 4x4, K+N,4"exh. ,2-40 gal. aux. tanks

 

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Russ, definately a good investment. When I had my bed built I got an aux. tank built in the front under my sleeper. We did basically what you have already been told. Came out of the tank to a ball valve (to shut off fuel for maintenance), into a spin on type fuel filter from NAPA, to a 12V fuel pump from Autozone, then T-ed into the vent line close to the tank. Both of my filler necks were relocated to the side of the headache rack on my haulin' bed. When I use the main tank, just flip the switch and filer back up without stoppin'. They other day I was fuelin' up and a lady stop filled her car up with gas went in paid for it came back out and asked if I was still fillin' up my truck. I smile and said yes ma'am but when I get through I can go about 1000 miles before I have to again... ... lol.

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99' 3500 SLT Med. Red Metallic 163" W. B. Cab & Chassis with custom haulin' bed, sleeper, rear light bar, stainless runnin' boards, stainless cow catcher on front, 5" dual stacks behind sleeper, hadley "bully" air horns, galaxy 44 c. B. with texas star 350 and wilson 5000 whip, etc... ...

 

[Archive]

Added an auxiliary fuel tank in the bed of my truck. Ran a line from the new tank through the bed and connected it to the vent line. Put a ball valve and filter in line so I can gravity feed into main tank. Works good EXCEPT when main tank fills, the gravity from aux tank will force fuel out of the regular filler neck when the main tank gets completely full. You have to watch your gauge and turn off the aux tank when main tank fills or it will run out the filler neck through the vent tube in the filler neck which is now connected to nothing. I know this may be hard to follow, but I'm sure some of you have done this and experienced the same problem.

How can I fix this?

It also makes the main tank very slow to fill since it is unvented and the air can't get out as fast as the fuel is going in.

Thanks for your help/advice.

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99 3500 QC 4X4 5sp 3. 54 K&N air filter, DiPricol gauges, 275 hp injectors, Pacbrake, Westin nerfs, GN hitch, Tekonsha Brake controller, Mopar seat covers, Husky mats, silencer ring removed, Draw-tite front receiver

[This message has been edited by Ninearrow (edited 06-24-2000). ]

 

[Archive]

Did you remove the hose from the vent line and hook up to the line going into the tank? If so you could hook up a hose to the top end of the vent line and run it back to the top of your aux. tank and tie it in. This would solve the transfer problem and the overflow problem but if you try to fill the original tank, it may blow diesel back on you unless you remove the cap from the aux. tank. I think the way most people are doing it is to weld a new nozzle on the filler line and the vent line and tie into them. I believe you can remove the upper end of the filler nozzle/vent line from the fender well to do this. bg

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White 99 3500, QC, 3:55, auto. most options except leather, Line-X bed liner, fiberglass running boards Ranco 9000s, bug shield and window vents, black vented 5th wheel tailgate, aluminum tool box, 100 gal. aux. fuel tank not mounted yet.

 

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Russ99
I have a tank set up just as you are talking about. To tee into the fill and vent lines I went to Tractor Supply and bought plated insert fittings for spraying use. On my '01 it took 1 1/2 inch for the filler and 3/4 inch for the vent. These are the male thread by insert type. A 3/4 black tee with an adapter from the auto parts store is used in the other opening in the tee. On the fill line I used a 1 1/2 inch coupling and drilled ond tapped it to screw a hose adapter fitting into and then cut a couple of the ridges off to get it to fit in the hose between the filler neck and the tank.
Larry

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Ram Rod
'01 3500 white quad cab sport 4x4 ETH DEE SLT+ 4:10s posi Pac brake tow/camper pkg.
35' holiday rambler 5th wheel

 

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. 02 from an amateur.

I made a two port manifold from brass part that I could simply screw together. I cut a section out of the vent line and inserted the manifold.

The top port got connected to the vent on my 50 Gal aux tank. The bottom port went to an electric fuel pump and valve. I found on my first truck that gravity feed was great when the tank is full but was too slow when nearly empty.

A side benefit of the electic pump is that you can hear it rattle when it is sucking air so you know when the tank is near empty.


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John S. '99 QC 1T 4. 11 A/T Leather Driftwood, 50 Gal aux tank/tool box, gearvendors, BD brake/autolok, BD ISB comp, guages.

Just a Little BOMBed and liking it a lot.