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308 Fuel Flow and filter/pump swap

Discussion in '308/328' started by mr308gtb, Nov 22, 2020.

  1. mr308gtb

    mr308gtb Formula Junior
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    So as previously noted in my other threads, my 308 is dead, lack of fuel. I got the decline and airbox off, and will ultimately rebuild and tune my carbs. It's on my bucket list...

    I disconnect one of the banjo bolts in the fuel line daisy chain. Started the car, which has a 1/2 tank of fairly old fuel in it, and nothing, no flow to the banjo bolt. I hear the fuel pump buzzing and the fuel lines are not collapsed or messed up.

    So. Where should I disconnect next to see if fuel is flowing? I want to replace the fuel filter and pump, they are old.

    Should i just take it all apart and I guess fuel should be flowing from the hose coming out the gas tank going right to the filter?

    Can someone explain what the little vacuum backflow thing does.

    Can I blow a little compressed air through the fuel line running up to the carbs to make sure it's clear of any debris.

    Thanks
     

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  3. lm2504me

    lm2504me Formula Junior
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    I would get rid of the plastic fuel shutoff valve. They do fail and shut off fuel flow. Connect from fuel filter to carb inlet.
     
  4. mr308gtb

    mr308gtb Formula Junior
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    Richard, what is the plastic shutoff valve?
     
  5. mr308gtb

    mr308gtb Formula Junior
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    There is a plastic T on the line going from fuel pump to carb.
     
  6. lm2504me

    lm2504me Formula Junior
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  8. mr308gtb

    mr308gtb Formula Junior
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    Thanks for the diagram. Yes, that's my exact setup. For my info, can someone explain what the little saucer thing does.
     
  9. lm2504me

    lm2504me Formula Junior
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    The fuel pump output pressure keeps the plastic flow valve open. If the fuel line from the fuel pump were to rupture, it would reduce the fuel pump pressure and cause the valve to shut, thus stopping fuel flow. These valves can fail closed even with pressure from fuel pump.
    A good way to get stranded. Just remove it and plumb accordingly.
     
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  10. lm2504me

    lm2504me Formula Junior
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    Oops, again it is a metal valve. It is a one way direction valve. They go bad. A USA item.
     
  11. mr308gtb

    mr308gtb Formula Junior
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    Ah thanks... so when fuel is flowing out from the pump, it creates some vac back to that valve and holds it open so fuel can keep flowing, kind of like a circular thing with some safety feature. I see your reasoning for eliminating it.

    So please tell me, if I disconnect the line at the inlet to that valve, fuel should come out (basically coming from the tank, passing through the fuel filter... gravity pressure?

    I am going to disassemble all these pieces, make sure all my fuel lines are clear, swap the fuel filter and the maybe swap the fuel pump (but at least have a new spare).
     
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  13. mr308gtb

    mr308gtb Formula Junior
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  14. mr308gtb

    mr308gtb Formula Junior
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    Ok, read a few more posts... so in all likelihood since my fuel pump is buzzing like it has for 20+ years. My little check valve is probably plugged up (and maybe shot). I can redo the connection to bypass,

    What do I do about the little T connection. Seems like changing that line that runs from the fuel pump outlet to the carb is kind of a *****. Are there any other options that would be safe? can I leave in the T, but somehow cap a little stub piece of hose? Any other thoughts?
     
  15. lm2504me

    lm2504me Formula Junior
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    I use a hose clamp on the hose from the gas tank. I bought a set from Harbor Freight. They work great. Remove the Tee fitting. Connect fuel line from filter outlet to pump suction. Connect hose from carb inlet to pump discharge. If your hoses are old, then a good time to replace them.

    The one way valve works on fuel pump pressure keeping it open for pump suction. If fuel pump pressure drops too low then there will be no flow from the filter to the pump suction. Hence a ruptured pump discharge fuel line. These one way valves fail over time.
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  16. mr308gtb

    mr308gtb Formula Junior
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    Yes, I see the hose clamp for when working on the car. I'm saying is there a solution if I dont want to remove the T. if I can just jump in a straight piece instead of the T. I guess having that extra joint there could create a potential leak.

    How hard is it to replace the line going from the pump outlet up behind and to the carbs?
     
  17. lm2504me

    lm2504me Formula Junior
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    Very easy. Use Tyraps to hold in place.
    Purchase new fuel hose, the existing looks old and damaged.
     
  18. Nuvolari

    Nuvolari F1 Veteran
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    I would re-plumb the entire fuel system from the tank to the carbs eliminating that valve and replacing all of the hoses for new. This is a very simple and straightforward job. A spool of fuel line is available from your local auto parts store (make sure it is FUEL LINE and not coolant line). Ensure your battery is disconnected and ground yourself to avoid sparks while working in a well ventilated area with a fire extinguisher handy.
     
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  19. mr308gtb

    mr308gtb Formula Junior
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    Thanks Rich
    Thanks Rob!
     
  20. BigTex

    BigTex Seven Time F1 World Champ
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    I will add a fuel pump can be "running" and still not be pumping fuel.

    I might start with that, and replumb the lines as discussed.
     
  21. mr308gtb

    mr308gtb Formula Junior
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  22. Nuvolari

    Nuvolari F1 Veteran
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    Your fuel system would need to be really nasty to have the in tank filter get clogged. I would check that last as it is a real pain to get to and a replacement one is shockingly expensive. Start with the low hanging fruit like re-plumbing the system (good maintenance anyways) and replacing the fuel filter.
     
  23. mr308gtb

    mr308gtb Formula Junior
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    Got it. thanks Rob... Seems like where I disconnected the banjo bolt at the carbs, I will need all new copper crush washers...

    anyone know where to buy these things just based on the size. I have the old one and can measure...
     
  24. Nuvolari

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    https://www.mcmaster.com/sealing-washers/metal-sealing-washers/

    I personally prefer the copper ones and am not a big fan of the fiber ones. If you are really in a pinch you can always re-anneal the old washers by heating them with a torch until they are cherry red and then letting them cool. It will discolor the washer but it will work good as new
     
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  25. mr308gtb

    mr308gtb Formula Junior
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    Big fan of you Rob!

    I'll let you know how my carb rebuild goes when I am done. I'm making progress, but take my time, just on weekends - but now that everything is open, it should go quick, once I get the fuel lines replumbed and the car running again!
     
  26. mauriciocaste

    mauriciocaste Rookie
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    +1 Replace the fuel filter. Also, replace all the hose clamps to the ones you have on pump / filter as I see some serrated ones by the carbs which can crack the hoses and leak when old. I'd suggest that once you have replaced hoses, clamps, banjo washers, and put everything back together, don't start the car. Just turn the key to active the pump and go over every connection point making sure there are no leaks. I do this twice.
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  27. mr308gtb

    mr308gtb Formula Junior
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    I did some work tonight. I bypassed the check valve and was still not getting fuel out to the carbs or to the hose that pull vac sonthe check valve. Fuel was running out my fuel filter... so conclusion, my fuel pump is shot. It still buzzes, but not getting any pressure out.

    So!!! What do I do for new pump. Indont see they make the expact same one?

    Which one should I buy? I saw the facet gold pro, but what size? Then I see I need some elbow fitting of a certain size??? And do I need some sort of pressure regulator as well? And then what about the connector. This seems like a major f'in pain in the ass.

    Anyone do it recently? Have the info?

    Thanks
     
  28. Nuvolari

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