I recently purchased a used 93 379 with the 3406b cat that has the older gravity-fed fuel crossovers at the bottom of the tanks, but the passenger side tank has been plugged at the outlet and it's only drawing off the driver's tank. I would like to get them both back in proper working order but am unclear how they are plumbed.
Years ago I had run over something on the highway in an international cabover and ripped the crossover line off but was able to turn off the valves and limp it to the next truck stop. Now after thinking about how vulnerable that setup is I have been considering looking into upgrading to top draw, but is that even possible for these older trucks? Has anyone here done that or has any advice? Is it a pita and expensive or should I just leave it as is and fix the original low hanging crossover?
379 fuel tank crossover questions
Discussion in 'Peterbilt Forum' started by Dennsco, Dec 27, 2020.
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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
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Thanks for the reply Roger, I am not very knowledgeable on the fuel setup for these petes, and since most of the lines are missing except the main draw and return to the drivers side I have to make new ones and figure out how to route them properly so I can use both tanks. I am guessing I need a fuel line splitter valve and a return line splitter to equalize them both.
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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
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Thanks Wore out! I am working on it today!
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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. -
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! -
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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. -
Flint1, Roger McG, Oxbow and 1 other person Thank this.
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