379 fuel tank crossover questions

Peterbilt fuel tanks draw from the bottom there is no standpipe to draw fuel from the top. The crossover line setup was used by peterbilt for years. Fuel tanks not balancing could be the vents on top of the tank

 

Real easy. Put a tee at left fuel tank outlet. Run right fuel tank to it. Run the 3rd out let of tee to the motor. Let all the return in the left tank which is where it currently is

 

Incorrect -- Peterbilt, nor any other diesel powered vehicle, draws fuel from the cross-over line; this is not only illegal, but you wouldn't want to do it since you'd be changing fuel filters every week due to water & other junk.
Older trucks with dual tanks -- manufactured before mid-1994 -- drew fuel from the top of one tank, returned fuel from the engine to the opposite tank, and had a simple cross-over line between the bottom sumps of each tank (usually with a ball valve on each tank); dual-tank trucks manufactured after 1994 drew fuel from both tanks at the top & returned fuel from engine to both tanks and had no crossover line between the bottom of the tanks.

 

I realize this is an old topic, so my response here is more for reference.

The OP can do one of two things. He can simply unplug his cross-over line, and the truck will run as it should and equalize tank levels properly.

OR -- he can completely eliminate the cross-over by installing a simple tee with lines to pickups in both tanks, and installing in the return line a high-flow return splitter valve with lines going from it to an open 1/2" NPT port on the top of each tank. NOTE: THESE RETURN LINES MUST BE EXACTLY THE SAME LENGTH OR FUEL LEVEL WILL NOT EQUALIZE PROPERLY. A simple 1/2" NPT plug is then screwed into the bottom sump on each tank to eliminate the cross-over.

I converted my 1994 Pete to dual-draw/ dual return just like this, and it works great -- and is a bit of a safety modification, since I don't need to worry about ripping out a cross-over line!

 

good sir are you to tell me that every Cat powered Peterbilt that had a crossover between the tanks and drew from the bottom were not only unicorns but were illegal? I had a 1989 Pete cat powered B engine drew from the bottom of the tank with a tee 1 end up to feed engine 1 to passenger tank.#10 fuel line up #10 across. My 1991 Pete same way, My 1993 Pete 3406B same setup. Return to top of tank # 6 fuel line to top of drivers tank. Shall I discuss my MY 1994 and 1996 Pete 3406E Cats that draw from the bottom to a tee on top of the Transmission.

 

I went back & checked the regulation again, and I am mistaken there (see below, quoted direct from the regulations)

49 CFR 393.67(c) (5) -- Fuel withdrawal fittings. Except for diesel fuel tanks, the fittings through which fuel is withdrawn from a fuel tank must be located above the normal level of fuel in the tank when the tank is full.​

I must have skipped the words "Except for diesel fuel tanks..." when I read it. So, for diesel, I guess it is legal -- but I still contest the advisability of drawing fuel from the crossover, since you are going to be drawing in every single drop of water and plugging up fuel filters in nothing flat. And for that reason, I have to doubt your claim any truck manufacturer would willing design a fuel system to draw fuel from the bottom of the tank.
In fact, my old 1995 IH 9400 had a 3406E and it had a dual pickup/ dual return fuel system -- top draw -- right from the factory.

 

Well believe it because if it was CAT powered in a Pete during the B model era that’s how she came. Main reason is the B uses a diaphragm style lift pump, it performs way better if fed instead of having to draw. They also return so little fuel that the high flow return splitter you speak of was or could be a problem. This system also always equalized. I have never had a big issue with water or sediment but I keep good caps and lines on my vent fittings. I also do not worry about a pick-up tube cracking or breaking off costing God knows what changing parts till they narrowed it down to that’s gotta be it. There are pros and cons to both