Peterbilt 379 Fuel line diagrams

Most 96 379s draw fuel out of the bottom of both tanks thru 2 equally long hoses then into a T then going to fuel-water separator. Now it makes it way thru the engine. When the engine has used what it needs, the excess fuel exits the back of the head thru a single line. This line makes its way toward the fuel tanks. Before it gets to the fuel tank it is sitting between the frame rails and goes into a splitter (cant remember part #) it's a glorified T fitting that sends an equal amount of fuel into two hose of equal lengths that return the fuel to the top of the tanks. "bottom draw top return"

Its best to have 4 shut off valves, each tank gets 2 valves one on the bottom line and one on the top
There are other varieties top, draw top return with a stand pipe
Bottom draw with a crossover line. I think they quit using that by 96

 

The hose of equal lengths is an important part of the above post. probably the most overlooked part of when the tanks quit equalizing.


Good luck finding a Pete master repair manual….

 

Here's what I have on my buildsheet. '89 379 w/ a mechanical N14

Lines are: Part#, Description, Qty. I copied from a spreadsheet so it came out a little off. When the dealer printed the buildsheet some lines got cut off or wrapped to the next line down. I'm still in the process of sorting that out

If there's and opening parantheses "(" but no close there was info that got cut off. CTL at the end of a part number means Cut To Length

ETA- Forgot to mention that the fuel tank switch on the dash just switches which tank the gauge reads. It doesn't change which tank the fuel comes from

1100-302-A46 **NOTE-FUEL DRAW & RETURN LINES
**NOTE-FUEL DRAW & RETURN LINES FROM TEE TO FUEL TANKS MUST BE THE SAME LENGTH
SK18584 DUAL DRAW/DUAL RETURN

26-02735CTL, Hose Assembly, Wire Braid, #10, 1
26-01536, Socket (#12 Fitting) re (#12), 2
26-01551, Hose Fitting Nut (#12), 2
26-02682, Nipple (#12 Fitting), 2
GC2, 26-010 " #12 Press Hose, 10

FUEL SUPPLY LINE FROM TEE TO FILTER
26-02730CTL, Wire Braid Medium Pressure Hose Assembly (#10), 2
26-01535, Socket - Hose Fitiing (#10) Wire, 4
26-01550, Nut (#10 Fitting), 4
26-02681, Nipple - Hose Fitting (#10), 4
GA4, 26-01526 PRESS HOR .) 0, 20

FUEL SUPPLY LINE - FUEL TANKS TO TEE
26-02060CTL, Medium Pressure Wire Braid Hose, 1
26-01539, NIPPLE (#8 FITTING), 2
26-01534, Fitting - Hose, Socket (#8), 2
26-01549, Nut - Hose Fitting (#8), 2
26-01521, Elbow - Short, 90 Deg (#8), 1

FUEL RETURN LINE - ENGINE TO TEE
26-02724CTL, Hose Assy, Wire Braid, Med Pressure, 2
26-01534, Fitting - Hose, Socket (#8) Braid, 4
26-01549, Nut - Hose Fittting (#8), 4
26-02680, Nipple - Hose Fitting (#8), 4

FUEL RETURN LINE - TEE TO FUEL TANKS
26-02116, Connector - 90 Deg (3/8" MP X #10, 2
26-01715, Straight Connector (1/2" MP x #8, 2
26-01912, Connector, 45 Deg (1/2" MP X #8, 1
26-01779, 90 Deg Connector (1/2" NPTF x #8 Flare), 2
22-01379, CLIP RUBBER CUSHIONED, 2
22-00517, CLAMP-CUSHIONED 1", 2
26-02855-008, Tee (1/2" FP X 1/2 FP X 1/2" FP), 2
26-01650, Straight Connector (1/2" MP x #10, 2
26-02808, Connector - Elbow, 45 Deg (#12), 1

 

Replace the crossover valve.