I am putting an auxillary fuel tank in my bed and looking for input on best way to tie it into the main tank. Is there an auxillary tank connection on main tank or do I need to tap into a line? I am planning on running a pump and filter between the auxillary and main tank with switch in the cab. Any ideas and or pics????

Hello Woody, this job is not for the weak hearted. The way I handled it was:

Buy the six port switching valve from JC Whitney. Your vehicle has no fuel pump in the tank...it sucks the fuel just like the older vehicles did. You must cut the two fuel lines running from the main tank to the engine area (the larger one is the supply and the smaller one is the return) and use flexible fuel lines to connect the switching valve to the main tank and the aux. tank. Be sure and use in-line DIESEL fuel filters between the tanks and the valve. The transfer switch needs 12VDC for operation, and also a DPDT switch in the cab.

As you can see, this is a pretty big job for the basic mechanic. If you feel you have the skills then go for it. I have used this procedure to connect a 60 Gallon fuel/toolbox combo from RDS (northern hydraulics) in three Duramax trucks and one gasoline truck with excellent results.

Good Luck!

yesterday I ordered a 98 gallon tank from Transfer Flow ... I chose it largely due to the fact that it is DOT approved and comes with everything needed to install it and from what I have been told, it also somes with a good set of install instructions :cool2: ... the above mentioned caution is well taken, their sales rep. told me to expect a 6 hour install :eek:

Jim

Thanks for info......I am going to get to 6 way valve. I will try to take pics and post how it goes.

Thanks for info......I am going to get to 6 way valve. I will try to take pics and post how it goes.

OK, good luck. A few hints are in order:

1. When you cut the steel fuel lines you will need to have a source of compressed air ready to go because the diesel will start to siphon from the main tank. Of course you will have some sort of container to catch the flow! Take the fuel cap off of the main tank so that when you blow the compressed air into the line (to empty the line and stop the siphoning) it will have a place to disperse to.

2. When connecting to the larger steel line (supply) use 7/16th inch fuel line, Not 5/16th.

3. If you want a fuel sender, order the one from JC Whitney that is for the Stewart-Warner guages....33-240 ohms. You will need to turn the resistive unit backwards from the way it is mounted on the sender to get it to work properly.

4. Read the owners manual to learn how to re-prime the system and remove all air from the fuel lines.

5. Plan on a lot of time, this is not a quick job.

Don't forget to run Aux tank through the fuel heat exchanger! My installer did'nt and I had some problems this summer in the heat out west!

Hi Drfab1967, just curious...what kind of problems? I tapped into the lines after the return fuel cooler for the aux. tank. I guess you COULD tap the lines between the cooler and the engine. Thanks.

I think they call it "out gassing." Had 3/4's fuel in the aux tank and could only get "bubbles" out of it! I took the return line from the engine and fed it to the intake of cooler, then ran the return side of the cooler to the switching valve. That way all fuel goes through the cooler. problem solved! Of course the poor thing may need a "jacket" this winter. :eek:

Very Interesting....I'll keep my eyes open for this problem. Thanks for the info.

Northern Tool has a gravity feed aux tank install kit for diesel tanks. The one they list is for Ford and Dodge, don't know if this kit will work on GM or if the kits mfr makes a kit for GM. If you're interested, here is the link.
http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=6970&productId=200315501&R=200315501

Northern Tool (northerntool.com) has a gravity feed unit to keep the main tank full automatically. The unit they have is listed for a Ford and Dodge, but maybe the mfr has one for GM apps. No switching, no screwing around with any factory plumbing, other than the filler neck.

wassup Wood! Isn't that your idea for the auxillary to refill your main tank? The previos posts are for a switched set of tanks. If you use that Northern setup is it DOT approved if it can be switched closed to avoid overfill? Also when your ready to do it I know someone that makes a great laborer!

Well, I had an aux tank installed in Houston, and they used one of those 6 way valves. That valve failed switching on the pickup side. ended up feeding what was left in aux tank to the main tank over filling the main tank. Emergecy repairs on the side of the road crawling around in diesel fuel is no fun. I also had aux tank pickup problems...all done by someone who does this for a living. I will NEVER have a aux tank like that again. In my opinion, I would always want the fuel pickup from the factory tank, and do a transfer via fuel pump from aux to the main tank. I ended up tieing mine in to the filler neck. I also suggest a return line from the filler neck back to the aux, in case the pump is on to long.

Yes, I plan on running the aux tank to the main tank. I am going to put a fuel solenoid in-line that is connected to 12v ignition only, so that it wont overflow accidently. After looking at my install more, I plan on tee'ing into the main fill neck and keeping a closed system by running vent line into a tee in the vent line. Both fill and vent lines are very accessible.