fj60 Carb adjust screws, what do they do?

Discussion in '60-Series Wagons' started by alvin9, Aug 2, 2008.

  1. alvin9

    alvin9

    Messages:
    236
    Location:
    Pasadena CA, SoCal.
    There are four of them. I have till Wed. If cant do it i will bring it to MArk in Burbank.
  2. Marc311

    Marc311

    Messages:
    937
    Location:
    Northern Virginia
    Idle
    Fast Idle
    Idle mixture
    AC Idle up (I believe).

    Not sure I would attempt anything until you grab (or download) the FSM.
  3. 2mbb

    2mbb SILVER Star

    Messages:
    4,520
    Location:
    WC, CA
    The screw on the right side of the carb (next to the valve cover) is the idle mixture screw. The one on the front of the carb adjusts the ac idle up. The two on the back of the carb are for idle speed and fast idle speed.

    The procedure for setting the idle speed and idle mixture is described in the attachment. I usually start with the idle mixture screw turned out (counter clockwise) 1 1/2 turns from it's seated position (turned all the way in). I turn the mixture screw in 1/4 turn increments (starting with counter clockwise), and wait for the rpms to stabilize, and conintue this in one direction until the rpm's maximize. I use a handheld tachometer to measure the rpm's. If I go a 1/4 turn too far (rpm's start to decrease), it's easy to find the maximum by turning the screw back the 1/4 turn. Once I'm close to the maximum I might do 1/8 turns (e.g. half as far as the 1/4 turn).

    You set the fast idle screw to get the desired idle speed when the choke is pulled out.

    If you set the AC idle up too high (screw it in too far) the idle will become unstable the AC is turned on. I have mine adjusted so the idle speed increase from 650 to about 1000 when the AC compressor engages.
    lean drop 2.JPG
    Last edited: Aug 2, 2008
  4. cbmontgo

    cbmontgo SILVER Star

    Messages:
    2,864
    Location:
    Colorado
    Not to hijack, but which screw would adjust the carb for altitude?
  5. Cruiserdrew

    Cruiserdrew SILVER Star

    Messages:
    11,984
    Location:
    Sacramento, CA
    Does not exist. The 60 has a HAC built in that I think advances the timing a bit. I've never been convinced it does much.

    The way I think about the Aisin carb is that it isn't really adjustable, except for idle mixture. The main and secondary are only adjustable by disassembling the carb, and swapping out the jets. The other screws are just set screws that adjust how far the throttle opens under various conditions, like when the choke it pulled or the ac comes on. They don't adjust fuel mixture at all.
  6. cbmontgo

    cbmontgo SILVER Star

    Messages:
    2,864
    Location:
    Colorado

    That is what I thought too, but after I moved to Colorado, people have told me that I need to tune my carb for the altitude. It does fine up here, but I was wheelin' at 12,000' altitude a few weeks back and my engine died. Others with the Aisin who are from Colorado can go above that altitude. I am not sure what the difference is, but theirs somehow can make it higher than I can go.
  7. 2mbb

    2mbb SILVER Star

    Messages:
    4,520
    Location:
    WC, CA
    The HAC does advance the timing, but it also leans out the primary hi/lo and secondary hi speed circuits. Maybe your HAC isn't working properly?
    hac schematic.JPG
  8. hank14

    hank14 SILVER Star

    Messages:
    2,229
    Location:
    Texas
    ...Or until 2mbb posts up another excellent scan or download of the FSM. Thanks for always being there to help! :cheers:
  9. NocalFJ60

    NocalFJ60

    Messages:
    3,547
    Location:
    San Francisco Bay Area
    Why do you think you need to adjust it? Failing smog?

    If it hasn't been rebuilt ever, then take it to Mark and start there. He rebuilt mine and would recommend him.
  10. JLH911

    JLH911

    Messages:
    2,369
    Location:
    So. Cal
    X2 on having Mark rebuild it...you won't regret it.
  11. fliphkd778

    fliphkd778

    Messages:
    990
    That's scary, "lean drop"?
    Does this explain the method, or the result? I don't want leaned out cylinders...

  12. NocalFJ60

    NocalFJ60

    Messages:
    3,547
    Location:
    San Francisco Bay Area
    I think more the method. It is only adjusting things for idle.
  13. cbmontgo

    cbmontgo SILVER Star

    Messages:
    2,864
    Location:
    Colorado
    Yes, I am thinking that may be the problem. I am going to buy a new HAC.

    I rebuilt the carb will all Toyota parts 2 years ago, and it runs perfectly. I think the HAC or something thereabouts is the problem at high altitude.

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