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My 78 has a Carter Quadrajet, which seems to operating fine. It starts well from hot or cold, runs fine and the plugs are a nice biscuit colour. I have one question though regarding the choke pulloff adjustment, which is bugging me even though it doesn't seem to be giving me a problem.
As I understand it the adjustment screw is meant to adjust how far the choke flap opens once the engine fires. However, on my car the choke opens by about 1/4" regardless of where I place the adjustment screw. If I screw the adjustment lever fully to the front of the car it pushes the green lever forward and opens the choke plate by 1/4". As this photo shows, if I back off the adjustment screw the choke still opens by 1/4" but there is now a gap between the adjustable lever and the green lever (afraid I don't know the correct names for these parts!).
Given this, how do I correctly adjust the system? Or do I have something else wrong here?
From: At my Bar drinking and wrenching in Lafayette Colorado
John -
The 1/4" adjustment is correct. If the choke does not change position when you turn the screw it is because the tang on the green lever is hitting the choke pulloff housing and being restricted in its travel. Bend the choke pulloff bracket slightly so the green lever tang does not hit it.
Hi Lars, I know that 1/4" is correct, but I'm confused as to why I can't set the gap to less than 1/4" if I wanted to. It seems to me that when I wind back the adjustment, the choke is held open by the air flow through the carb, I can just push the choke flap closed a bit without moving the green lever, should I have this slack in the system? Which way are you saying I should bend the bracket (I am assuming you mean the one that is connected to the adjustment screw) towards the green lever or away from it?
From: At my Bar drinking and wrenching in Lafayette Colorado
John -
You have something interfering with the travel if it cannot be adjusted. Visually identify what part is hitting what and bend it for clearance. It's usually the pulloff bracket that has the pulloff positioned too close to the tang on the green bracket, preventing its full range free movement. It is obvious if you look at it and move things with your fingers. Airflow cannot hold the choke open against the choke coil spring force - the choke coil force should hold the choke firmly closed when cold, and it can only be cracked open by the force of the pulloff. The pulloff has full adjustment range from not opening the choke at all, to opening it almost 1/2". If it does not, you have a mechanical interference problem that you simply need to visually identify and correct.
When I press the throttle to set the choke, the choke coil does hold the choke flap closed. Then when I start the engine the pull off opens the choke flap. In the photo above you can see that with the engine running the flap is open about 1/4" but the choke pull off isn't actually touching the green tang. I don't get what is holding the green tang fully over. There is some backlash between the green tang and the choke flap, so with the adjuster wound out (as it is in the photo) I can close up the choke flap to about 1/8" without moving the green tang. Is the green tang meant to be spring loaded to take up this slack?
From: At my Bar drinking and wrenching in Lafayette Colorado
The green lever with the tang is connnected directly to the coke coil with no play or slop. The only play/slop in the system is the lever on the choke shaft with a small slot to allow some play and movement between the lever and the choke intermediate rod. The green tang should be in contact with the contact lever on the choke pulloff unitl the engine starts to warm up and the green lever drops away from the pulloff lever.
Lars
Think I've discovered what was wrong (well actually I don't think anything is wrong at all, it was just me not realising what was happening). If I set the choke fully, so it's on the the second ratchet position, as in this photo, then the pull off does open the choke plate and I can adjust how much it does so.
What I think was happening before was that I was starting the car (which wasn't particularly cold because it's summer) and gave it a quick rev to get my alternator to start charging, then walked around to take a look at the choke setting. By this time the choke had dropped down to the first ratchet position, as per this photo, and the pull off was no longer in contact with the green lever. So as far as I can see everything is working properly, except perhaps for my alternator which always needs a quick rev of the engine to start it charging. Thanks for the helpful advice Lars.
From: At my Bar drinking and wrenching in Lafayette Colorado
John -
Good job on the examination and inspection. Yes, what you are saying is correct: If the choke has been cracked open by the thermostatic choke coil by more than 1/4", then the pulloff will not have any effect on the opening. In your photos, all appears to be in correct order and operating condition, and all your components are original stock components, lending me to believe they should be operating as they should (aftermarket components are often the culprit when things don't work right). That's a nice, original carb in unmolested condition - very unusual to see on many of the European vehicles.
Lars
choke pulloff adjustment
