Aux Tank install on 2020

[Wiredawg]

So I read the tread on Cummins forum, and I think I am going to give Ltngdrvr's install a go. I have everything from the previous owner's install except the pipe with the check valve in it. Does anyone know if /where you could purchase just the brass valve? I would prefer to pull the filler tube and simply weld a bung in it, then re-install with out the extra pipes, etc.. and since I already have the shutoff valve on the tank and the vent / fuel lines, the only thing I need from the kit is the check valve. I am having a hard time with spending almost a $100 on the RDS kit for that valve. Is it just a simple differential pressure valve?

If you want to try my useless setup, bought all the hardware at Northern Tool and bought the fuel line at Advance. I just happened to go with the size that the factory TDS fitting supported.

EDIT: I dont keep RDS valve open, but when primary tank gets down to 1/4 tank, I open it and forget it. Never leaked a drop.

BTW, my application is for a Cab and Chassis. but the RDS tank doesn't care.

Cheers, Ron

 

[Ltngdrvr]

So I read the tread on Cummins forum, and I think I am going to give Ltngdrvr's install a go. I have everything from the previous owner's install except the pipe with the check valve in it. Does anyone know if /where you could purchase just the brass valve? I would prefer to pull the filler tube and simply weld a bung in it, then re-install with out the extra pipes, etc.. and since I already have the shutoff valve on the tank and the vent / fuel lines, the only thing I need from the kit is the check valve. I am having a hard time with spending almost a $100 on the RDS kit for that valve. Is it just a simple differential pressure valve?

Call RDS and I'm sure they will sell you just the check valve, just tell them you are moving the tank to a new truck.
It has a check ball inside with a float attached to the check ball to make it close when fuel reaches it.
By the way, the check valve is 1/2" NPT threaded, so you will need a bung that size welded to your filler pipe. And, it really needs to be installed where the check valve will be upright so the valve operated correctly.

 

[bcbender]

Call RDS and I'm sure they will sell you just the check valve

yeah, I'll try that.. I saw "parts" on their webpage but they didn't list the valve. I assume you have the "capless" fuel system on you 15'? no leaks w/o a fuel cap? I am new to this capless system.. take me a min or so to get the truck pump nozzles in / out.

 

[Ltngdrvr]

yeah, I'll try that.. I saw "parts" on their webpage but they didn't list the valve. I assume you have the "capless" fuel system on you 15'? no leaks w/o a fuel cap? I am new to this capless system.. take me a min or so to get the truck pump nozzles in / out.

No leak issue so long as you don't try to top off the main tank when filling up.
No issues caused by the aux tank install.
And, remember to always fill the main tank first, don't fill the aux tank then try and fill the main.

 

[bcbender]

yeah, that makes sense.

 

[bcbender]

OK, finally have a window to put the truck out of service to make the fuel filler pipe modification, I was looking at it last night and was not sure how to disconnect the DEF lines, as they seem to have some sort of quick connection and since I do not have the factory service manual yet, I don't want to damage anything. Also wanted to confirm from those who've done it that after removing the DEF tubes from the frame connection point and disconnecting the filler tube / vent at the tank / frame connection that I only need remove these 3 screws and I can drop the whole assembly?

 

[Ltngdrvr]

OK, finally have a window to put the truck out of service to make the fuel filler pipe modification, I was looking at it last night and was not sure how to disconnect the DEF lines, as they seem to have some sort of quick connection and since I do not have the factory service manual yet, I don't want to damage anything. Also wanted to confirm from those who've done it that after removing the DEF tubes from the frame connection point and disconnecting the filler tube / vent at the tank / frame connection that I only need remove these 3 screws and I can drop the whole assembly?

View attachment 127903

That's different than on my 2015, on mine I just drilled out the rivets that mount the fuel filler tube to the plastic flange at the fuel door. I didn't pull that whole assembly out with the DEF filler, so not sure how that all comes apart.

 

[Tuesdak]

And, remember to always fill the main tank first, don't fill the aux tank then try and fill the main.

This would be a bummer. I would use both high speed fill hoses at a truck stop and fill the aux and main tanks at the same time. Have to go slower on the main tank, but, the aux tank would take full speed. Putting in 28/48 gal is worth starting the second pump on the right and tossing the hose over the toolbox tank. Some auto diesel pumps are so damn slow I can pee faster than they pump.

The TransferFlow I had would use the vent line to fill the tank. Sometimes if it was running the transfer pump before stopping for fuel the vent line would still have fuel in it and cause the tank to burp fuel out.

 

[bcbender]

Now its getting interesting, I disconnected the filler to tank lines (bottom) and it was free down there. Well then I drilled out the two rivets in the back holding the filler pipe weldment to the plastic part and now it will not fit through the hole in the assy, the green flange on it the top side is bigger than the hole in the filler assy.... anyone ran into this one? Doesn't seem like it wants to come off and I think it's part of the capless filler? Looks like I still have to take the whole thing out so now how to disconnect the DEF lines? anybody?

EDIT: Looks almost like the filler pipe has to be "tipped" into the assy due to the shape of it. No where near enough room in there for that, not sure how to get the whole thing out either as its tight between the wheel house inner stamping.

o

 

[bcbender]

Another pic of the monster Im dealing with I miss working on my 04 it was simple... It sure doesnt seem like something that want's to be messed with..

 

[Ltngdrvr]

Another pic of the monster Im dealing with I miss working on my 04 it was simple... It sure doesnt seem like something that want's to be messed with..
View attachment 127919

WOW!
They sure complicated the hell out of that, didn't they???
If you had an exhaust tubing cutter, maybe you could cut the pipe for the inlet hose adapter without taking it all the way off.
I don't know, looks like a real booger.

 

[GBBrown]

I changed out my fuel door to a SS locking door..there was silicon holding the fuel housing assembly to truck bed that I cut loose using a hack saw blade. Whole assembly was loose then.

 

[bcbender]

Did you pull the assembly? I think I need to disconnect the DEF lines now and maybe pull the inner fender liner, now that the rivets are out, things have gotten more interesting for sure. Do you simply compress the green tabs and pull. I really dont want to damage the DEF lines, ... or any of it for that matter.

 

[Ltngdrvr]

Definitely pull the tire off and the fender liner out, opens up the working room a bunch.
I didn't do it when I pulled the filler tube on mine, and sure wish I had.

 

[bcbender]

As promised, I put this in awhile back but here are the steps I took.. I hope it helps someone out.

Step 1. jack up the truck, take off the left rear wheel and wheel liner if applicable ( remove all screws and push in then lift / tilt down to remove.

2 Remove the filler neck from the truck. Take the 3 screws off on the outside, remove the ground strap on the inside, both hose clamps on the fuel lines, and release both DEF tank lines.

3) Disconnect and remove the steel filler (leave the rubber lines in the tank) and cap the DEF lines to prevent contaminates from entering they system. (I used zip lock bags and rubber bands)

NOTE--> I cut the zip tie and left the tank vent in the truck as it seemed to be too hard to disconnect from the pump module. I left it and temporarily supported it with a hand clamp.


4) Remove filler neck out of the vehicle, you are now prepared to modify for the Aux tank filler port.

 

[bcbender]

Now with the filler neck on a bench, you can modify the part easily to add the port. One way is to cut the metal tube and add the supplied aluminum T with rubber hoses.. I chose to make a steel bung on the lathe and then drill a hole on the top side of the filler tube and TIG weld it in so as to prevent additional leak points.

Welded pipe with leak test plug:

Paint to protect from corrosion and check fit of fill port

 

[Cummins12V98]

NICE write up!!!

 

[bcbender]

internet is soo slow... there's more comming

 

[bcbender]

Now its ready to put back in the truck.

After install put the T in, use FUEL SAFE thread sealant and point it forwards to facilitate running the fill hose to the aux tank. (shown is installed with filler hose for AUX tank running to left front corner of the bed.

 

[bcbender]

Now to the topside......

Drill a hole to run the filler tube through,, I installed a AN bulkhead fitting so I could cap it when I take the tank out and prevent dirt, etc to enter, but this is not necessary, just make sure you protect the rubber line with a grommet at a minimum.

Finally when bulkhead fitting is installed, you can install the RDS (or other brand) tank and connect to the outlet port.. I kept a valve on mine so I could use the tank (or not ) when I wanted so I typically drive until my main tank is about 1/2 then turn on the valve,... the tank will slowly fill, but you burn it about 1/2 as fast as it fill so I drove all day without it ever completely topping off... Tank filler port has a check valve so it will not over fill / flow.

NOTE... I can disconnect the AN fitting and replace with a AN cap when I remove the tank which is usually when I need the full 8' bed or not towing alot.