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?
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
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.
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.
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)
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.
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.
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.
How can I tell how much fuel is in my auxiliary tank?
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
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.
Is gravity feed legal?
You can gravity feed diesel fuel into your OEM tank but not straight to the
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.
How do I install the adaptor on vehicles with a double fill line?
You would install it the same way, cut out a section of the fill hose, install
the adaptor and clamp it down.
Do I need to secure the auxiliary tank in the bed of my truck?
Yes, use the tab welded on the tank and one bolt per side of tank.
Are the Auxiliary tanks vented?
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.
Do I have to ground the tank?
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.