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Secondary activation on 2.2's Holley 6520

Discussion in 'EEK! - Every Extended-K Car' started by Dodgem's Dad, Oct 29, 2017.

  1. Dodgem's Dad

    Dodgem's Dad Member

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    I pulled and rebuilt the carb on my '84 Reliant but want to resolve some questions before I install it.
    What triggers the secondary to open in my Holley 6250? None of linkage on the driver's side seems to work it and the vacuum pull on the back only moves it a bit. Manifold side of that throttle plate was really dirty too. Even though the drivers side throttle linkage rides against a nylon roller on number 2's lever it doesn't do very much. I have attached a pic from before the cleaning.

    I wonder too how I can check the operation of some components before I put the assembly back on the car. There is a vacuum solenoid on the front, a mixture control solenoid on top, and a throttle solenoid on the driver's side that were only removed and reinstalled. I wouldn't recognize if they were working correctly or not.

    Many thanks for any input,
    Justin
    BTW, the Dodgem in Dodgem's Dad is my '85 convertible with the 2.6 that I bought new, my only new car to date. IMG_20171026_155800034.jpg
     
  2. Best Answer:
    Post #3 by ImperialCrown, Oct 29, 2017
  3. 85lebaront2

    Level 2 Supporter

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    From what I remember on mine, the secondary is opened by venturii vacuum in the primary, this is a standard Holley progressive system dating back to the model 4000 4 barrels in the early 50s. To test, hold the primary fully open and blow air through from the top along the side near the secondary diaphragm. There may be a small angle cut brass tube, this is the signal port. Some also used an additional port in the secondary to "snap" it open once there was enough flow.
     
  4. ImperialCrown

    Level III Supporter

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    With the primary throttle fully opened, then the secondary throttle should fully open manually. The secondary won't open until the primary is opened first. There should be a small o-ring to seal the vacuum secondary chamber to the carb body.
    There is a cold operation lock-out solenoid to vent secondary vacuum and keep the secondary from opening when the engine is still cold (for good warm-up drivability).

    The plastic vacuum canister to the choke pull-off is a vacuum delay. If you apply vacuum, it should then slowly and partially open the choke plate smoothly with no binding. Once opened, everything should hold vacuum and not leak-down.

    No vacuum diaphragm should leak.

    The combination vacuum diaphragm/electric solenoid idle speed control should bump up idle speed with the solenoid once started and at warm idle and bump up idle speed again by vacuum when the A/C is engaged to compensate for the drag of the compressor. After shutting the engine off, the solenoid should release the throttle to a more closed setting (below normal idle speed) in order to prevent dieseling/run-on.
    The brass grounding tab should contact the throttle lever at warm idle to tell the PCM that the throttle is at minimum.

    The fuel mixture solenoid with the tan and green wires is controlled by the PCM according to the O2 sensor reading. It is only used when warm and off-idle (cruising) in closed-loop operation. At full throttle, the engine enters open-loop and the O2 signal is disregarded.
    It is a 'duty-cycle' on the ground side of the mixture solenoid. It should 'blink' a low-current test light or 'flick' and analog meter pointer. A digital meter will just show numbers bouncing all over the place.
    The fuel control solenoid has more 'on' time when more fuel is needed (i.e. - hill climb or acceleration). It will have more 'off' time at an economical cruise or coasting down a hill.
     
    BrianinMpls likes this.
  5. Dodgem's Dad

    Dodgem's Dad Member

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    Wow! This is the best information and exactly what I have been looking for. The various manuals, shop, Clymer, Chilton's, and the rebuild instructions left me without a clear answer. Thank you both. I think I can take it from here, but if you could stop the rain it would help.
    Justin
     
    85lebaront2 and ImperialCrown like this.
  6. 85lebaront2

    Level 2 Supporter

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    It's raining here too, so can't help you there.
     

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