'75 Eldorado Choke (?) Adjustment

[Benji808]

Hey all!

Rebuilt carb (thanks Cliff for the parts and expertise!), and it's doing much better. Easily starts when cold (2-3 pumps and ~5 seconds cranking), and seems to idle, run, and accelerate great. Only problem area I'm seeing right now is immediately after a cold start...the engine runs ragged for maybe 30 seconds - really rough, with smoke from the tailpipe - then it evens out and is great. The issue does not recur on subsequent startups - only when it's been setting for a while.

I'm guessing this is related to the choke adjustment...I currently have the choke set at two clicks clockwise, which is consistent with the shop manual...how should I approach making adjustments? It's a very narrow window to troubleshoot so some experienced advice would be appreciated.

Thanks!

[Kenth]

Sounds like a choke pull-off issue. Either need replacement or adjustment.
Remove aircleaner before next cold start and look for a slightly opened, about .160", at rear of chokeblade when engine starts.

[Benji808]

Alright - I'm new to this so talk slow and thanks for your patience

Picture attached of engine off (I started it right after taking this picture and it started immediately on crank after sitting for ~6 hours, no issues- yay for no leakdown!!).

Is the choke pull off the brass "bowl" thing on the left or the right of the picture?

By chokeblade, do you mean the forward "butterfly" flap? Does this get adjusted by turning the screw on top of the right brass piece?

Thanks for helping!

[Kenth]

No worries!
Your carb has two choke pull-offs, one primary on the right in your pic and the one to the left is the secondary p-o.
When your engine starts the arms on both p-o´s should pull into the pull-off´s and open the choke-blade (upper "butterfly") some.
The primary p-o is adjustable by turning the screw on top, just as you thought.
Look for .160" at rear end of choke blade checking the primary p-o.
The rear p-o should open the blade .130", this is easier to check adjust on the bench since the front p-o needs to be disconnected and and a handhold vacuumpump used. Adjustment for this means to bend the the link. I would leave it alone for now. If it don´t pull it´s arm with engine running you might as well disconnect the rear p-o and plug the vacuum source.

HTH

[Cliff Ruggles]

You may find it difficult if not near impossible to vacuum test the rear pull-off.  Many have a tiny "bleed" hole in them to delay operation as they are only a back-up for the primary pull-off.  Others have such a tiny hole in the vacuum tube where you attach the hose that they may take quite a while to apply so often appear as they are not working when you test them with a vacuum pump.

Focus your efforts on the primary pull-off.  Make sure that it holds vacuum and is set to unload the choke flap on a cold start to the correct angle so the engine continues to run on the fast idle but not too rich or too lean.

They even made some primary choke pull-offs with a bleed hole in them but they are not nearly as common as the rear varieties.

Here I don't often use the rear pull-offs unless the set-up is all OEM.  They are not needed if you have a good working and correctly adjusted primary pull-off.

Below is the pull-off that I sell for the later Q-jets that used an adjustable primary pull-off.  They have a straight inlet and easy access to the restriction.

The ones being sold elsewhere with the bent tube are useless and there is no restriction in them so they will not work well.......Cliff

[Benji808]

This is tremendously helpful - thank you both!

[old cars]

So just turn the adjustment screw on the front pull-off counter clockwise to lean the choke on cold start.
Try half turn at a time.

[Benji808]

Turning the screw does not seem to have any impact on the choke blade position (after a cold start, I've taken it 3-5 turns in both directions). Would that imply that the pull-off is bad and I should replace?

[Kenth]

Is the arm in pull-off pulled at all when engine is started?
If not, time for replacement.

[Benji808]

Alright - it is sucking in, but I think I found the issue with the choke itself:

The inside of the choke cap has a metal coil. At the end of that metal coil is a "square" shape. Is it correct that the choke flap lever should sit INSIDE the square?

Because mine wasn't - the choke lever was resting on top of the square, so the choke could only reliably be adjusted one direction (I think I made it this way when I was messing around a couple months ago).

Started it up and it seemed to idle much smoother that first minute; I'll get more chances to test but seems like it was that simple error.