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Fuel system help

Discussion in '1982-Present GM Diesel' started by afroman006, Aug 2, 2005.

  1. afroman006

    afroman006 1/2 ton status

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    I am plumbing the entire fuel system in my 6.2L diesel truck and need some help. First off, what sending unit do the fuel tank use? 2 or 3 hoses? If its 3, whats the third for? Second, the fuel goes from the tank to the lift pump, lift pump to filter, then filter to injection pump correct? D, I have the spin on filter bracket and it has 3 connection holes, the third is for the fuel return hose if I'm not mistaken, which is where I get confused.

    On the Hayne's diagram, it shows that the injectors' return lines all connect to a single return line, but where does that line go? It shows that it splits and goes to the fuel filter and the tank, how does it do that? Thanks for the help.
     
  2. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    The return line on the injectors goes to the fuel tank only not the filter there is also a return line off the injector pump to the tank . The sending unit has 3 lines one is to take the water out of the tank . lines come oof the tank to the lift pump then to a primary filter then secondary then to the IP hope that helps
     
  3. savagek5diesel

    savagek5diesel 1/2 ton status

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    not too sure...

    i just did a bunch of fuel line work on my 6.2 a week ago and the fuel tank line goes into the primary (water seperator) filter, down to the lift pump, back up to the secondary filter, and then into the IP. And the 3 lines out of the tank are exactly what 6.2MAN said.
    If memory serves me correct, on the front of the block there is a metal fuel line that the small, rubber injector fuel return lines connect to. That line splits, so some of the fuel return goes into the bowl of the IP and any excess is then pushed back down to the fuel tank. But i'm not 100%.
    I've found that the haynes manual is really hard to go by when you need it most because it vaguely describes what you need it to. Like the diagram you talked about...... that's a rough discription of a diesel fuel system in general. The 6.2's setup is a bit different.
    Good luck, and i hope this helps.
     
  4. afroman006

    afroman006 1/2 ton status

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    Man it looks like I'ver gotten myself in a can of worms. I have a spin on filter bracket but was not able to locate any fittings to screw into it today so I decided to go with the box type filter and bracket that I also have. Is this box filter a "primary" or "secondary" filter? On the truck it came off of, it was between the lift pump and injection pump. Sounds like it was the "secondary" filter, but in that case, where is the primary filter? I'm doing this whole thing from scratch and do have a parts truck to look at but its a cab and chassis with no rear axle and a fuggin huge utility bed on it so its kinda hard to trace the fuel lines all the way back to the tank.

    To make this party even more fun, the sending unit I am using is from a gas tank. Does the third connection still serve the same function? If this is a problem, I can get the sending unit out of above said parts truck. Thanks for the help.
     
  5. savagek5diesel

    savagek5diesel 1/2 ton status

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    Primary is whatever is on the firewall, the secondary is bolted to the back of the intake manifold. On my truck (screw on primary) the 5/8ths fuel line that screws into the filter connects to a rubber hose about 4inches off the frame that then connects to the main fuel line to the gas tank.
     

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