FJ40 Running Poor

Discussion in '40- & 55-Series Tech' started by Red Fox Ranch, Jul 29, 2005.

  1. Red Fox Ranch

    Red Fox Ranch SILVER Star

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    So here's the story, bought an FJ40 from California that was originally from Wisconsin, PO had bottom end rebuilt, head, etc. I bought it, trailered it home. Ran like s***. So I have been doing all the things that needed doing: adjusted the valves, reset the timing, had huge vacuum leak because PO had no PCV valve, replaced that, replaced the diaphragm for the secondary barrel. Checked the vacuum with a guage and it's that's great. Still runs really poor. When I am out on the road trying to get up to speed it hesitates like flat spots and like the fuel delivery isn't up to par, and when I hammer down and the secondary barrel kicks in it almost always backfires back through the carb. The PO said he rebuilt the carb, but his poor skills of assembly point me to assume he didn't do it correctly, so I guess the only thing left I can point at is the carb needing a good rebuild, what do you folks think???

    Any help would be greatly appreciated!
     
  2. andrewfarmer

    andrewfarmer

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    is the accelerator pump working?
     
  3. atoyot

    atoyot

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    Timing's good. Valve clerance good. Fuel pump and filters good. Vacume good. I would say the PO screwed up the carb when he attempted to rebuild it. I would say either rebuild it yourself ot send it to Jim Chenoworth or one of the reputable carb builders to rule the carb out.
     
  4. Romer

    Romer fatherofdaughterofromer Moderator

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    Try the Carb adjustment setting in the FAQ. Takes about 20 minutes and at least you can rule out that its not set properly
     
  5. 65swb45

    65swb45 Elder Statesman Supporting Vendor

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    In many cases, if not most, when there is a backfire, the carburetor is the victim, not the culprit. Keep this in mind.

    You mentioned a secondary diaphram, so I am going to assume that we are talking about a 2F carb. Do you know how many inches of vacuum it is pulling at an idle? If you have access to a vacuum guage, you should also see what the vacuum drops off to when you stab the throttle.

    If your vacuum drops suddenly, and below a certain point, then the fuel in your air-fuel mixture may fall out of suspension in the intake manifold, causing a flat spot even if your accelerator pump is working properly.

    I would also advise doing a compression check. With a fresh bottom end, you should have very good compression. If your rings have not seated, then the compression will be off, and so will the vacuum.

    Hth
     
  6. Red Fox Ranch

    Red Fox Ranch SILVER Star

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    So I forgot to mention it is a July of 76 FJ40 with 2F.

    I am new at all this so I may sound a little stupid, but be patient with me and help me out...

    Where is the acclerator pump located at?

    How do you access the carb settings in FAQ, do you me on this forum?

    Fuel falls out of suspension? Can you elaborate on this? What causes it, what fixes it?

    Thanks for all the help!
     
  7. Pin_Head

    Pin_Head

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    If the compression is OK, I would go ahead and rebuild it properly. The only adjustments are for idle speed and idle mix and it sounds like your problem is not at idle.
     
  8. Red Fox Ranch

    Red Fox Ranch SILVER Star

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    Any more help?
     
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