Fuel Return Lines

[mu2bdriver]

Is there an easy way to determine which fuel line is the return line to the tank without uncapping it to check?

The reason I ask...
I have an aluminum in-bed fuel tank which I would like to plumb into one of the existing fuel tanks via the return line. I was planning on running a line from the aluminum tank to the front or rear return line with a fuel pump between the two. Mount a switch in the cab to turn the pump on and pump fuel into one of the underbed tanks to be fed as normal. The aluminum tank has a venting cap. Do I even need a fuel pump hooked up or will gravity flow and the venturi effect of the return fuel be sufficient to suck the bed tank fuel into the underbed tank?

Or is there a better way for me to go about this?

If someone could post a picture of the fuel line schematic that may be helpful also.

Thanks in advance.

 

[79jasper]

I would worry about it backing up the return line creating back pressure.
I believe a lot just gravity feed, but depends how fast you want it to fill.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[icanfixall]

All supply lines for fuel are 3/8 tube and all retruns are 5/16 tube. Any return line from injector to injector is either 3/16 or 1/4 inch. That pretty much tells you what all the lines are on the engine or supply or returns to the tanks.

 

[snicklas]

Another thing to remember, that fuel is "heavy" sitting up in that tank in the bed.......

Travis had one in E-1 and left on a trip, drawing from the in bed tank, and using the ~40 in the factory tanks as "emergency backup"..... he drove MANY miles on that tank and had forgotten to turn the electric pump on. It ran fine, with the weight of the fuel, it fed the engine fine........

Another thing, make sure you draw from the top of the tank with some kind of pickup, like factory tanks do...... this was another lesson learned from that big tank...... when he first put it in, he drew off the bottom of the tank, from a bung at the bottom of the tank. He had plumed in an additional Pollak valve so all he had to do was flip an additional switch to go from factory tanks, to bed tank. The weight of a full tank ~100 gallons of fuel, at ~7.5 lbs a gallon, that weight would blow right through the pollak valve, no matter where it was switched to......... and once something that heavy starts moving (flowing) it doesn't want to stop......... he switched to a top draw with a "straw" to the bottom of the tank...... problem solved. I don't remember him having any issues with the return going to the bed tank.

I would say, go one of 2 ways...... plumb it in with valves as a third tank, or find a transfer flow tank fill tube, and plumb it in with a pump. But you have to watch if you set it up as a transfer...... if you don't pay attention, you WILL overflow the factory tank and start pumping fuel out of the fill cap........

Personally, if I wanted to add a tank (with my 2 diesels, this would not be the easiest, the Ex...maybe..... but) I would plumb it is with a set of valves, either manual, or a second factory style valve, one input coming from the factory valve, that normally went to the engine, and the second to the 3rd tank. So your factory front and rear switch would still do whey they always have, but a new switch would go from factory, to aux......... or they do make 3 way valves, 3 ins to one out........... choice is yours............

Or for those that don't have another tank, and wanting to stretch fuel range, (I wonder if Greg50HO still has the measurements) is pick up a factory Excursion tank. I mounts in the rear, same place the factory rear does, and it is 44 gallon (I know this for certain, just put 42 gallons in mine, and it wasn't "empty" yet). The bad thing about this mod, you loose the spare tire carrier, just like the Bronco 38 gallon tank. The Bronco carries the spare on the back door, and the Excursion carries it inside, in the sidewall like a 70's station wagon.