Standard starting procedure / choke setting Q-jet

Discussion in 'The Venerable Q-Jet' started by srb, Jan 24, 2022.

  1. srb

    srb Well-Known Member

    I have a 1969 Rochester 4-barrel on my 1969 430 engine (7029241) bought from this forum. It was rebuilt 3 years prior and was sold working flawlessly.
    I've just rebuilt my engine and I replaced my old Holley with this (for me new) carb. I was able to to complete the break-in procedure. During that I also advanced the timing a little bit and connected the choke rod. (divorced choke). It ran very well, so I think the carb was indeed rebuilt well.
    But now I have a real hard time starting the engine again. My battery isn't great, so I'm going to replace it, but it I was able to start the car the first time with this one. The temperature here is ~40F (5C)

    So I basically have two questions;

    1 - Is there more to adjust on the choke than the rod?
    I've adjusted the rod as per manual. But I was wondering if there are some internal settings to be made? I've got the feeling it starts more difficult with the choke connected, than without, so perhaps another adjustment should be made.
    Rochester 4MV_1.png Rochester 4MV_2.png
    2 - What is the normal starting procedure?
    I've seen an old commercial on Youtube that explains how a car should be started.
    Press the pedal once to the floor, lift your foot from the pedal and turn the ignition.
    Is that your experience as well, or do you pump a few times more?
    With the Holley without choke I could start it with 2 pumps.​
     
  2. 70skylark350

    70skylark350 Jesus loves you unconditionally

    Every engine has its own procedure in my experience. I need to pump a couple times then hold the throttle about 1/4 while cranking.
     
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    With my Q-jet, anything more than 2 days, and the fuel evaporates out of the float bowl. The choke should set with one pump, make sure that is happening and that the choke blade fully closes. There should be some resistance when you poke it with your finger. If there is fuel in the bowl, it should light off and run, then run at fast idle. Make sure the front choke pull off is operational, as it immediately opens the choke blade about 1/4” so the engine will run without loading up. This is really important because the engine will choke out without it. The same pull off slows the secondary air valve opening so the engine doesn’t bog when transitioning to the secondaries.
    Make sure there is fuel in the bowl, accelerator pump squirts should be strong. Check that when you check the choke blade closing.
    I manually fill my float bowl when the car has sat for awhile. I have a squirt bottle of gas, and fill it through the vent.
     
  4. pbr400

    pbr400 68GS400

    My GS doesn’t have a choke, but my El Camino (‘85) still has its factory Qjet. Until recently it was starting according to the manual-mat the pedal once, release and crank. It recently started acting up-running like it was being smothered and dying until it would warm up. Turns out one of the linkages on the passenger side was gummed up and not dropping forward, thus holding the choke flap closed even though the pull off was trying to open it. A little spray lubricant and worky-worky and it’s good as new. (Thanks, Starc!).
    Patrick
     
  5. srb

    srb Well-Known Member

    I rechecked and adjusted the choke rod a little bit after all. And I rechecked the linkages, but everything moves freely.
    The battery was dead in no time, so I have to wait until tomorrow.
    A single cylinder fired occasionally, so I know I have spark.
     
  6. Brett Slater

    Brett Slater Super Moderator Staff Member

    There's also an adjustment you can make to the choke plate/rod that's found in the chassis manual and calls for the use of a pair of "duck bill" pliers.

    I can post a picture later when I get home.
     
  7. 12lives

    12lives Control the controllable, let the rest go

    You need to have someone start the car while you watch what the carb is doing and verify it. Take the whole air cleaner off and watch - As Larry said:"The choke should set with one pump, make sure that is happening and that the choke blade fully closes. There should be some resistance when you poke it with your finger. If there is fuel in the bowl, it should light off and run, then run at fast idle. Make sure the front choke pull off is operational, as it immediately opens the choke blade about 1/4” so the engine will run without loading up. "
    My car, I have to pump it a few times after the "choke is set" if it has sat awhile. Otherwise, one pump and it fires.
     
  8. Max Damage

    Max Damage I'm working on it!

    There is also a vacuum pull of that opens the choke a crack when the engine starts. If this isn't connected or working it can "choke" the engine.

    The start procedure is to press the gas pedal to the floor once. This should set the choke and if there happens to be fuel shoot a shot of it from the accelerator pump. If the gas is evaporated it should take a few more cranks to fire.

    There are also screw adjustments for the hot idle and cold idle, which can make a big difference in how the car fires up.

    Let us know? Maybe record audio of what it sounds like starting (or trying?)
     
    Darron72Skylark likes this.
  9. Brett Slater

    Brett Slater Super Moderator Staff Member

    If you need to adjust the choke blade:

    20220124_184803.jpg Screenshot_20220124-185022_Gallery.jpg 20220124_184750.jpg
     
    lemmy-67, Max Damage and srb like this.
  10. Dr. Roger

    Dr. Roger Stock enthusiast

    On mine, no matter how long it sits, I pump it once to the floor then keep my foot off the accelerator and she starts right up. One thing that you have to make sure is that the choke plate snaps all the way closed when the engine is cold. Any slight opening and it will be a bear to start. Once the engine fires, the vacuum starts, then the primary pull-off will open the choke plate a little. Of course, everyone is used to fuel injection now days and instant starts, but with this these old carbs, it takes a few seconds of cranking to get them started on a cold start. After she starts, I have to let her run on fast idle for a little before I goose it to bring the idle down, otherwise rpms are too low and she'll die.
     
    Max Damage, techg8 and Brett Slater like this.
  11. Tomahawk

    Tomahawk Platinum Level Contributor

    https://buick-riviera.com/servicemanual/064-40-60.pdf

    That's the entire 4MV carb section from a '71 manual; the description of choke operation begins on pdf page 10 (manual's page 64-49).

    Did you maybe use all the gas when you were breaking the cam in? Don't be offended...I'm only asking because that's the kind of stupid sh*t I do
     
  12. srb

    srb Well-Known Member

    Haha, yes it was empty after breaking in, but I've added more fuel, so that's no issue.

    I'll check the choke blade as well.

    If the problem remains I'll film it.
     
    Brett Slater likes this.
  13. Cliff R

    Cliff R Well-Known Member

    "One thing that you have to make sure is that the choke plate snaps all the way closed when the engine is cold."

    This is the most important part of the deal. On a cold engine moving the throttle does two things. It allows the divorced choke to tightly close the choke flap and the accl pump puts fuel into the intake.

    The engine sh0uld roar to life immediately. IF not you either don't have the choke set correctly (not tightly closed) or your accl pump seal is shot.

    Never assume that the pump seal is good as this new fuel is very hard on them. The "blue" seals swell up quickly in contact with ethanol and will not allow fuel past them, or they tear or roll off the end of the pump, so little or no pump shot for cold starts. This is why I don't use them and use a seal that is 100 percent impervious to ethanol and lifetime warranty. I tell folks this all the time when they call up here bellyaching about poor starting after the car sat a few days. They go on line and read posts from folks telling them that the bottom plugs are leaking. That is NOT the issue 99 times out of 100, and it wouldn't matter anyhow. I could hand you a bone dry rebuilt carburetor and the engine should roar to life when fuel returns to the fuel bowl and you are pumping the throttle to put some into the intake.

    Most of these no start scenarios are not an empty fuel bowl they are going to be fuel delivery to the carb or accl pump related.......FWIW.......Cliff

    IMG_2619.jpg Pump seal failure.png
     
    FLGS400 likes this.
  14. srb

    srb Well-Known Member

    Ok thanks everyone for the comments, appreciate it. Lots to be learned.
    I took myself with the manual to the garage once more and decided to check all choke settings.

    First, I've made a video of the accelator pump. Looks right to me.

    The choke plate is really closed (set up per manual):
    20220125_143223.jpg

    Then, I checked the "choke rod adjustment".
    If I understand the manual correctly I should have .130" where my drillbit is located.
    Cam follower is on the second highest step and the rod on the choke plate is on the bottom of the slot. The rod needed some adjustment:
    20220125_144545.jpg

    "Choke unloader adjustment".
    "Push up lightly on vacuum break lever". To be honest, I'm not sure what that means.
    What I did was wide open primary and then I should have .325" where my drillbit is pointing:
    20220125_152912.jpg

    It was way off so if I understand the manual correctly I had to bent the tang to which my awl points. Gap is now correct.
    20220125_151437.jpg

    I've probably drowned my engine now with all the pumping. And it looks like I'm missing a screw.
    Unfortunately my battery is delayed a day, so I'll have a go tomorrow.
     
  15. Brett Slater

    Brett Slater Super Moderator Staff Member

    Resistance on the closed choke blade?
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    With the choke plate fully closed, manually operate the choke vacuum break with your finger. Push the link all the way in. It should open the choke blade against thermostatic spring tension.
     
    Brett Slater likes this.
  17. srb

    srb Well-Known Member

  18. BadBrad

    BadBrad Got 4-speed?

    Ditto what Larry said on the bowl being empty after a couple days evap time. Today's fuel is formulated for a closed (to the atmosphere) fuel injected fleet. For me two seconds of starting fluid down the throat is about all that's necessary at start up to allow the pump to put fuel in the bowl.
     
    PCUB likes this.
  19. Cliff R

    Cliff R Well-Known Member

    Accl pump shot looks a little lame from what I can see of it.

    The carb looks like a commercially "remanufactured" unit, not a rebuilt carburetor.........
     
  20. srb

    srb Well-Known Member

    Hm ok, I'll keep that in mind. In case something is off during use.
    Remanufactured is not good?
    About the seal; here in the Netherlands I'm using 95 octane, 10% Ethanol gas. Lower octane isn't available. A quick online search tells me that the US uses both 10% and 15% ethanol?
    I could also buy 5% here; that would be preferred?
     

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