Sounds like you are gravity feeding so don't open the cap when it is full. I have a aux tank but I use a small pump with a normally closed solenoid and I have never had the code pop up but I do wait until the main tank is about 1/2 empty before I start to transfer and I shut it off when it gets 3/4 or 7/8 full. Also from your pics it doesn't look like you used a bulkhead connector to pass the fuel line through the box - be careful you don't wear a hole in the line.

 

Yep, gravity feed. I’m thinking of installing a 12V electric block valve with a switch in the cab. I thought about just using the manual block valve. I was thinking how hard could it be to get out on one of my stops to open it (while towing 5th wheel on a long trip). But what if it’s raining really hard or some other inclement weather condition I don’t want to deal with? It’s also been suggested to leave the valve open, gauge goes to E (and check engine light comes on) then when auxiliary tank gets empty and main tank level starts dropping gauge starts working again. I’m guessing check engine light would stay on until it was reset though. Decisions, decisions!

 

takes about 5 on/off with key then will clear itself
my 11 and 15 wouldn't set unless driving for about 2 hours straight. My 18 will set after about 20 minutes ;(

 

I took that valve off of mine I couldn't get any fuel in with it.

 

same here!

 

Now I am reading where if you use a 12 V solenoid fuel valve that when the power off is normally closed and with power on it’s open, the valve heats up fairly quickly. You can’t just drive for hundreds of miles leaving the power to the solenoid till the valve is open, it just overheats. So unless I can find one that doesn’t get hot that’s not a possibility either.

 

Mine works fine - it is not on for hundreds of miles though. These valves were used on vehicles with dual tanks to switch the tank that feeds the engine - pretty sure they do have them on for hundreds of miles

 

Yes, you are “overfilling” from the reserve. A “manual” valve is best, IMO. It will probably never fail for hundreds of cycles.

A “transfer pump” could be solution..https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/fuel_pumps/carbureted_fuel_pumps/carbureted_electric_fuel_pumps/parts/12D

 

Or this..

U.S. Solid 3/8" Brass Solenoid Valve - 12V DC Normally Closed, VITON S

U.S. Solid normally closed (N/C) electric solenoid valve is constructed with a durable brass body, 3/8" female threaded (NPT) connections, and strong VITON gasket. Suitable for use with hot or cold water, natural gas, air, very low viscosity fluids (< 20 cst) and gasoline or other petroleum...

ussolid.com

rig it to gravity feed into main tank when you notice the tank getting low.

keep plenty fuel in main tank.. it helps cool the pump..

 

I'll see if this is what my buddy needs for his truck. We're installing an aux tank after we finished installing the suspension and kmc wheels on the current Silverado project. He's been looking for a better solenoid valve.

 

I don’t know what kind of solenoid valves the truck world uses, but if you want something that will do 100% duty cycle with no problem, get one meant for industrial use. I’ve seen Asco and Skinner solenoid valves run energized in chemical plants for months at a time. They aren’t cheap but you won’t have to worry about leaving it powered open for a few hours straight.

 

See my Build thread here many other guys here have done the same thing. A few pages in I installed the Aux tank price went up on the valve I paid $26. I Am also installing a gauge and sending unit

Amazon.com: Standard Motor Products FV1T Fuel Selector Valve : Automotive

Buy Standard Motor Products FV1T Fuel Selector Valve: Selector Valves - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Single to Dually

Well I have been slowly and I mean slowly gathering parts. after realizing I Had to much money wrapped up in the 2500 it was not worth starting over so I figured build what you got. So here is whats been done over the summer. All new fuel lines New Red head steerign box Complete front end via...

www.duramaxforum.com

 

i think the OP has the six tank backfeeding the primary tank. So, this valve you used would choose which tank supplies the fuel pump.

my solution controls flow from AUX to primary.

 

Ok works fine for me to run main down to 1/4 full area then open the auxiliary tank block valve. Problem is I have a vent fuel cap, which looks like a radiator cap, but it builds up pressure inside auxiliary tank if block valve is closed. There’s another 2” plug in top I was thinking of installing a vent in. Don’t like that pressure building up, I live in 120 degree summer heat.

 

Yes, vent the top of the aux tank. I usually wait till the factory fuel gauge reads about half then stop and adjust valve to fill just fast enough it keeps up with what your burning. If you fill while guage reads full it will error out.

BTW love the tires. They'll last long time pulling.