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My U.S. 77 308 won't start - I'm determined to fix it...

Discussion in '308/328' started by mr308gtb, Oct 2, 2020.

  1. mr308gtb

    mr308gtb Formula Junior
    Rossa Subscribed

    Sep 12, 2004
    533
    Full Name:
    MeestahBig
    Hi -

    my 1977 308 won't fire up. If I use starter fluid or pour some gas into the carbs, it fires up and runs, but dies in few seconds. So I know its running. Engine is good and strong. Fuel isn't really too old, as to where I thought I would have been having this issue. Maybe its a year old, and was sitting a few months, now several more months. Never had an issue starting her in 20 years.

    I've decided, I'm going to learn how to resolve this myself. A fellow F-chatter sent me a great article on the Weber 40 carb. Before I take these carbs off and clean them, I'd like to try and logically conclude the blockage is actually at the carbs. I will then remove/rebuild and sync as needed. Im fine to spend money on tools.

    Please humor my dumb questions - and I really appreciate the help. I am passionate Ferrari owner.

    1) how can I determine if the fuel blockage is indeed at the carbs or before... can I pull off a fuel hose (or several fuel hoses) going into the carbs and see if its pushing out fuel when I turn the car on? I can hear the fuel pump going when I turn the key. If I cant get any gas to the carb inlet then I will look downstream for collapsed hose, line filters, fuel filter, etc.

    2) would it be odd that all 4 carbs are so jellied up that the car simply won't even start right now?

    3) is there any sort of vacuum I should be testing on any of the hoses to determine if the system is compromised?

    4) I never ever use the choke, never in 20 years have had to. I see based on the manual that the choke is a totally separate fuel supply within the carb? Should I try and use the choke? I just thought of this tonight after trying to get this car started several times this year.

    Sincere thank you...
     
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  3. mr308gtb

    mr308gtb Formula Junior
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    Sep 12, 2004
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    MeestahBig
    Starting from square one - I am at this stage with the trumpets and airbox on top of my carbs.

    http://308restoration.com/2019/04/refitting-the-airbox/

    The site owner - commented that getting this airbox back on was a *****, he even mentioned something about putting the car on the lift to get the hoses connected?

    1) Am I going to need a lift to rebuild there carbs? Assuming its not a fuel blockage downstream?

    2) any additional insight about removing this airbox and then putting it back on?

    Thanks.
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,900
    Texas
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    Steve Magnusson
    Do this:

    before considering disassembling/removing the carbs. Just pull the fuel feed line off the 5-6 carb inlet and run the hose into a jar or can. Turn the key "on", confirm audibly the fuel pump is running, and see if any fuel comes out. If yours is a 1977 US version you also have a pressure regulator (item Q in this figure) that can fail (and bypass the fuel back to the fuel pump inlet rather than send it up to the carbs):
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    PS If your fuel pump runs with just the key "on" and no one sitting in the Driver's seat = switch R has been bypassed (and most have been).
     
  5. cscott

    cscott Formula Junior

    Dec 31, 2002
    478
    New Orleans
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    Chris Scott
    When you turn the key on do you hear the fuel pump running?
     
  6. mr308gtb

    mr308gtb Formula Junior
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    MeestahBig
    yes, I hear the fuel running - like it always has for 20 years. A nice little hum! I'm pretty certain the pump runs even if I am out of the seat.

    @ Steve - ultimate dumb question - if looking at the rear of the car, which would be carb 5-6?

    Thanks.
     
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  8. mr308gtb

    mr308gtb Formula Junior
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    Also - how much fuel should I expect - will it be flowing, or just sort of pushing out slowly, or really gushing... I want to be prepared. I am sort of hoping the fuel lines are fine and its the carbs... Is there a fuel feed line to each of the 4 carbs or does it daisy chain? Thanks
     
  9. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    #7 Steve Magnusson, Oct 2, 2020
    Last edited: Oct 2, 2020
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    Daisy chain. See the table on page C13 of the 308GT4 WSM:
    The fuel pump should deliver 100 liter/hr at zero pressure (so about 1 cup in 8 seconds) -- this would be the condition for the hose feeding the 5-6 carb when disconnected. (The flow rate in the return line will be less because in that condition the pressure is not zero due to the "calibrated hole" in the fitting where the return line attaches).
     
  10. Patrick Dixon

    Patrick Dixon Formula Junior

    Mar 27, 2012
    784
    UK
    No, definitely not.

    It's pretty straightforward; just be careful not to lose any of the nuts or spacers down the carb trumpets when you remove/re-fit it. You could always tape them over if you have any concerns. The breather hose that connects to the underside should have enough slack that you can remove it relatively easily.
     
  11. rjd2

    rjd2 Karting

    Jul 28, 2016
    75
    Please forgive me and disregard if this sounds obvious; 2 things that may help:

    1-you mention seeing the fuel flow, so I'm going to gather the plan was to run the fuel pump with the fuel line downstream of the pump while disconnected, into a reservoir of some sort. Can do; probably a good idea to keep 2 fuel extinguishers handy.

    2-a fuel pressure gauge will allow you to monitor fuel pressure, of course, while keeping your fittings in place, thus testing the car. probably a good investment.
     
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  13. mr308gtb

    mr308gtb Formula Junior
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    Thanks everyone so far... I am definitely a tool guy... don't mind to buy any tools.

    Can I check any of the fuel lines without taking off the airbox? Steve's picture, clearly has the airbox off : )

    Great idea - a fuel pressure gauge... any suggestions one to buy? Basically - connect it inline and check the fuel pressure? what pressure would I expect to see if the fuel pump is okay and the filters/lines are clear (not clogged or collapsed) heading into the entry point to the carbs. whats the best place to connect it?

    I read a long fchat thread about the nuts and washer getting the airbox and air horns off... I will devise or buy some sort of tool, but its still unclear to me what to expect... can someone describe the stacked order of the parts that will be there? nut on top, then a washer, then airhorn body, then airbox body? I read you cant simply pull the airhorns off from the top, and that there is some rubber washer that falls out from the underside? But I have no clear vision in my mind of the stack... a simple hand drawing perhaps would be very helpful. boy I feel so desperate and needy!

    THANK YOU
     
  14. rjd2

    rjd2 Karting

    Jul 28, 2016
    75
    Any off the shelf fuel pressure gauge should get you in the door. Make sure it comes with an assortment of fittings; you'll obviously need metric. Can't see how this happens w/o the air box off. Look for a connection location. My preferred way to do this is to seat the gauge, run the fuel pump for 5-10 seconds, shut car down, and go over all fittings for leaks. It's not only a good habit, but safety first. Again, have at LEAST one extinguisher handy. You think you don't need it, right up until the moment you need it within 5 seconds. I find myself getting "project tunnel vision", where I just get in a groove, if that makes sense. Once you are sure you have a fuel tight system, leave the pump running, and check. On my Delorean, I think I saw ~60 psi? On a carb car, it'll be considerably less. Honestly, if you see anything at all, it's not gonna be the fuel pump. I wouldn't be surprised if these webers don't wanna see more than 4-6psi or so. Here's where the experienced guys chime in, I'm still way green on these cars.
     
  15. Brian Harper

    Brian Harper F1 Rookie
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    Feb 17, 2006
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    Brian Harper
    I would not make the assumption that modern alcohol fuels won't go bad in less than a year.
     
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  16. derekw

    derekw Formula 3

    Sep 7, 2010
    1,308
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    Derek W
    Don’t hope it’s the carbs as a bad pressure regulator or blocked line is a much easier fix. Push a ball of cloth into the carb throats if you are worried about things dropping in.
     

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