Auxiliary tank fueling issue

[CThomsen]

I have an 86 gallon transfer flow tank in the bed of my 2013. It has no transfer flow wiring or controller. I have it plumbed into the vent line of the main tank. I use an electric pump with a switch on the dash to transfer fuel. Problem is now when I turn switch on, no fuel goes to main tank. I unhooked line where it t's into vent line and turned pump on and got fuel to flow into container. I hooked another piece of fuel line to vent T and blew into it. Very little resistance but air came back through line when I stopped blowing. Could the vent line be blocked somehow? Should I use more air pressure to blow out vent line? Any feedback appreciated. Thanks
Chris

 

[DavidC]

No expert here but shouldn't it be plumbed into the fill pipe ?. Did you try loosening the cap on the fill to vent the tank so you are not pressurizing the tank. Just a thought.

Dave

 

[CThomsen]

It's been working great for over a year-30k miles. I took cap off of transfer flow tank. Main tank fill just has a plug which I also removed. Made no difference.

 

[DavidC]

So much for that idea

Dave

 

[Hoefler]

Plumb a return line in from the vent line on the main tank to the aux tank. Move the transfer line to the fill line. The main tank is much tighter than the old ones that had fuel caps.

 

[Doubleclutch]

I'm guessing there's a problem with air in the suction of the pump. Not always, but I've gotten a lot of bit quite a few times because of air leaks.

 

[CThomsen]

It pumps fuel to the T in the vent line. I really think the vent line has an obstruction because when I blow into it the air blows back at me. Am I safe to blow compressed air into vent line?

 

[Powder Extreme]

I teed my aux tank with a "Y" just outside of the fill neck, when the pump is running the fuel actually flows in to filler neck that way. Very simple to do, all I did was cut the steel vent about an inch from the filler neck and used some rubber fuel hose and clamps. I do not have vent lines between the two tanks tied together. The fuel caps (or flapper system) on each tank will vent to prevent too much suction or pressure in each tank. No need for complex plumbing, only one 3/8" hose.

Since then I have put over 20,000 miles on the truck using the aux tank every time and never had any problem whatsoever.

On my GMC Duramax I removed the fuel neck and welded in a tee for its fill line, however the pump shot the fuel across the filler neck and some of it went down the vent line and filled it up. After using my aux tank to fill the main and then draining the main as well, when I'd try to fuel the main tank at anything less than an absolute trickle the fuel would spray back because the vent was clogged with fuel and didn't allow air to escape. After letting the truck sit for a day two the vent line would eventually drain out enough I could once again fuel the truck like normal.

My guess is pumping fuel into the vent has done something similar. Just drive your truck for a while without using the aux tank and see if it clears itself up.

 

[CThomsen]

I've been driving it without using auxiliary tank for a couple of months. Tried to transfer fuel last week and nothing happened. Main tank has 1/3 tank of fuel and I have about 40 gallons in auxiliary tank. Do you think blowing out vent line with compressed air would hurt anything?

 

[Tuesdak]

I would put suction on the vent line first just in case there is a check valve in it. (Don't use and blow up your shop vac! Use a hand operated pump.) Otherwise, yes, you have a restriction like a kinked hose or debris plugging the hose. I assume you have the main tank cap off while playing with air pressure and if it has the new flapper capless fuel fill (I know nothing about it.) you need to make sure to have it opened up to where air isn't trapped in the tank.

I would do a visual inspection of the entire length of the vent hose for kinks. Use mirrors if you have to.

Blowing air though it will only blow debris out if that is the problem. It can also blow the hose off the tank or blow fuel back in your face so be careful. This will not fix a kink as it can open it up and tomorrow the problem kink will be back.

As noted above: fill the tank on the main filler. So fix the vent line so you can fuel the truck properly and move the aux fill line to the filler hose. If the aux pump was running before I stopped for fuel with the transfer flow it always burped fuel back onto the fender due to fuel in the vent line. Never cared for that aspect of the hook up - it's just quick and dirty to hook it up. Over the long run a shortcut to be avoided.

 

[CThomsen]

Well, it turned out to be one of those dumb ***** moments. The small inline fuel filter was bad and restricted enough fuel flow so that it would not transfer fuel. Replaced filter and fuel is flowing like new again. Thanks for all the suggestions.

 

[S.Morris]

I mounted a fleetguard water separator/ filter and a 3micron fuel filter after the transfer pump on my aux to the tank ventline. I only fuel the aux tank now...

 

[mfurrh55]

I've got a BF1259 on my aux. tank with water sep.