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Auxiliary Diesel Fuel Tank Installation Kit

     Having been and installer of auxiliary fuel tanks for many years I have decided to post a small how to web site as it pertains to one of the most common tanks used by not only my self but others. This would be the RDS Manufacturing auxiliary tank(s) and their gravity flow installation kit. I will deal with some of the most frequently asked questions regarding this setup as well as installation instructions.  

The one thing I'm asked more then any other is, do I need to remove the little black cap from the rollover valve / vent? 

Yes, if you do not remove this cap your tank will not work as it should. You can find more information on this in the Frequently Asked Questions part of this site.

1)              Auxiliary Diesel Fuel Tank Installation Kit. What is this?

   This device allows the diesel fuel to gravity feed from the auxiliary tank into the OEM (truck fuel tank) and prevents overflow with a rollover valve that comes on the fill pipe adaptor. This is designed to work with any auxiliary fuel tank with a 3/8 inch female pipe thread drain fitting. This kit comes with the fill pipe adaptor, fuel hose, hose clamps, and a shutoff valve. The kit is designed to allow fuel to fill the OEM tank with out causing overflow when installed correctly.

2)              Installation Instructions.

       Take your time and look where the original fill spout comes into the OEM tank on your truck. For Dodge and Ford the hose size will be 1 ½ inches. Chevy and GMC the hose size will be 2 inches. Carefully calculate how much of the fill hose has to be cut away. Remember measures twice, cut once. You cannot add hose back if you cut it to short without making a trip to your local auto parts store. Install the adaptor as horizontal as possible with the brass rollover valve upright. Secure the adaptor tightly with hose clamps provided.

      Now you are ready to install the auxiliary tank. Remove the aluminum plug from the drain and install the shutoff valve. At this point hook up the fuel hose and secure with a hose clamp. Now we will drill a ¾ inch hole into the truck bed where the shutoff valve will align when the auxiliary tank is secured to the truck bed. Run the fuel hose through the ¾ inch hole you drilled and attach it to the rollover valve on the adaptor and secure with a hose clamp.

     Now is the time to check for leaks and proper operation of auxiliary tank and installation kit. Fill auxiliary tank with fuel. Open the shutoff valve on the auxiliary tank, this will top off your OEM tank causing your fuel gauge to read full again, if not already. Look over all areas where you installed hose clamps looking for any signs of fuel leakage. Once you have determined there are no leaks you are ready to hit the road. While driving your fuel gauge will stay on full because fuel is flowing into the OEM tank as it is used. When you see the fuel gauge moving off the full mark you know the auxiliary tank is empty.

3)              Troubleshooting your installation.

   Sometimes for what ever reason things don’t go as well as we would like. Should fuel overflow from the cap of your OEM tank you will need to use the shutoff valve to stop the flow of fuel to your OEM tank. Run your vehicle until it reads ½ tank of fuel. Again open the shutoff valve to start the fuel flowing to your OEM tank as before. If the overflow problem persists call customer service at RDS Manufacturing (1-850-584-6898)

Some newer vehicles are equipped with computer operated gauges and will go into protect mode if the gauge does not move off the full mark in a selected time set by the manufacture. If you have one of these vehicles you will need to control the fuel flow by using the shutoff valve to refill your OEM tank.


Frequently Asked Questions

Q. What does the gravity Feed install kit consist of?

A. This kit consist of the fuel hose adaptor with rollover valve, fuel hose, shutoff valve, and hose clamps.

  Q) How does the gravity feed kit work?

A) Fuel flows from the auxiliary fuel tank through the shutoff valve and hose into the adaptor attached to the OEM tank fill hose. This fills the OEM fuel tank.

Q) How can I tell how much fuel is in my auxiliary tank?

A) Your OEM gauge on the dash board will read full until the auxiliary tank is empty. At that time your OEM gauge will start to move from the full mark towards empty.

Q) What prevents fuel from overflowing from my OEM fuel tanks fuel cap?

A) The adaptor you installed in the fill hose has a rollover valve that is designed to seal off the flow of fuel as it fills up into the fill hose.

Q) Is gravity feed legal?

A) You can gravity feed diesel fuel into your OEM tank but not straight to the injector pump.

Q) I have my gravity feed kit installed but I do not get any fuel flow, why?

A) Make sure you removed the plastic cap from the vent on the auxiliary tank you installed. Remember this is a simple gravity feed system and if the tank is not vented fuel will not flow. Also check to ensure there is no obstruction in the line or rollover valve which is rare.

Q) How do I install the adaptor on vehicles with a double fill line?

A) You would install it the same way, cut out a section of the fill hose, install the adaptor and clamp it down.

Q) Do I need to secure the auxiliary tank in the bed of my truck?

A) Yes, use the tab welded on the tank and one bolt per side of tank.

Q) Are the Auxiliary tanks vented?

A) Yes, All tanks have a rollover valve vent that is normally located near the fill. Make sure to remove the plastic cap to allow the vent to work.

Q) Do I have to ground the tank?

A) The bolts used to secure the tank to the truck bed should be good enough. Make sure the truck bed is grounded and if needed run a ground to one of the bolts used to secure the tank to the bed.