59 CDV - Not holding an idle... Carb?

[dcastine]

Hi Guys - I have 16 "shakedown" miles on my "new" Coupe de Ville - every one smiling from ear to ear, this is a cool car to drive. It's not as "big" feeling as I thought it would be and the visibility with all that glass is amazing!

It wasn't running very well, so I replaced the gas filters (One after the tank, and the one in the glass bowl), changed out the points and condenser, got a new cap and rotor, as well as new plugs and wires - she fired right up and kicked right into high idle - it sounded great!

Once it warms up and I blip the gas pedal the revs will come down and it'll eventually stall, it still won't idle. I've checked all the vacuum hoses, and the timing is correct.

I'm not sure how old or how much gas is in the tank, my sender is acting up. Last week I put 10 gals of 93 Octane and some Stabil in it.  When I look at the glass bowl - I see no debris, and the gauge still shows 1/4 of a tank.

I'm going to have the Carb rebuilt by a local rebuilder (Hobbs in Pelham, NH), has anyone tried a newer carb with a more conventional idle circuit (with an idle screw)? Or should I trust that the carb is at fault and all will be well when I get it back?

Thanks in advance!
Dave C

["Cadillac Kid" Greg Surfas 15364]

First of all the correct carbuor adjusting procedure is called out  in the shop manual, one of which I would strongly suggest you get.
It sounds like you might first look at the idle speed adjustment on the carburetor's throttle linkage side.
If the car will idle reasonably at fast idle then you might look at this first.  The screw is a hex headed/slot screw that is near the base on the left side of the carb, near the front of the base.
Find the screw and take a picture of it and post it so we can verify the right one.
Greg

[dcastine]

Hi Greg - I do have the manual and followed the procedure as best I could, I've attached a pic that I had on this laptop, if it doesn't show adaquately I can get another shot when I get home.

Thanks for your help!

Dave C

["Cadillac Kid" Greg Surfas 15364]

Dave if you can see the screw that is just about vertical with its head down with its toe (opposite end to head) riding on the cam of the choke plate linkage.  With the engine off, manually pull the throttle rod back until you can see the idle adjusting screw and reach it's head.  Try turning the screw in (clockwise) 1/2 turn at a time, starting the car and checking the idle speed each time.  Be sure the choke butterfly is fully opened and the carb is off fast idle.
Greg

[dcastine]

I'll check that again Greg, I did "play" with that screw for a bit but I didn't want it to change the cold idle speed too much. Once the engine was hot, that cold idle cam was way out of the way of the screw. I'll try and mess with it again tomorrow night. - thanks

Dave C

[Dave Shepherd]

The idle speed is adjusted by the large slotted screw between the mixture screws, front of the carb.

["Cadillac Kid" Greg Surfas 15364]

It's supposed to be Dave, but for what ever reason I have found the idle speed range this screw allows is very limited, and it might be expeditious to make sure we don't have some other problem before we get to the fine tuning.
Greg

[dcastine]

Thanks Dave - I'm aware that that large screw is the idle adjuster, but it has almost no effect on the idle speed. It only seems to change that large "sucking" sound that the carb makes.

Thanks Greg - I'm going to have the carb rebuilt, drop & clean the tank, install a new sender, replace/blow out the gas lines, and install new filters. Once all that is done, I'll install the carb, add 20 gals of 93 Octane fuel (and Stabil) and she where she is at that point.

Thanks guys!

-dc-

[dadscad]

On the Carter, the lone screw contacting the fast idle cam is used to adjust the cold fast idle when the choke is set closed. To adjust the hot idle, you use the large air bleed screw in the front center of the carburetor and the two mixture screws on either side. If your throttle linkage, TV rod and fast idle linkage are not properly adjusted, the air bleed screw may/will not function properly. To adjust the Carter you have to follow the shop manual steps, exactly, to correctly adjust the hot idle rpm and mixture. It all starts with adjusting the throttle linkage properly, first, to be sure the throttle plates are fully closed before you start turning mixture and air bleed settings.

HTH,
David

[dcastine]

Thank you David, I'll re-read that portion in the manual again 

'appreciate the reply!

Dave Castine
59 CDV, 57k miles

[william_b_noble]

it may not be the carb - check for air leaks into the intake, including a faulty pcv system if installed, that will cause same symptoms

["Cadillac Kid" Greg Surfas 15364]

That was the reason for my suggestion to try and get the curb idle speed up with the cam screw.  It will help isolate the real problem.
Greg

[Brett Cottel]

Judging by the pic....the carb looks like the fellow needs a rebuild anyway. I think that the carb is critical to your enjoyment of the car and the ease of use. I used Daytona parts company for a total remanufacture of my 55 Rochester. Very happy with the results. HTH
Brett

[dcastine]

I think you're 100% right Brett - I started the car today and gas was pouring out of the Accel Pump and down the front of the carb, taking it to a rebuilder on Monday!

[The Tassie Devil(le)]

That sounds like a faulty Needle Valve and Seat, and therefore in need of a rebuild.

Bruce.

[dcastine]

I agree Bruce, I hear no difference in the way she runs when the two adjuster screws are turned all the way in, no hope for an idle when that happens. She fires on a click of the key, I hope she'll run real nice when I get the carb back - can't wait to really drive her before she goes away for the winter!

Thanks
Dave

[cadman49]

dave-my 2 cents. everything those guys said are true. but here comes my take. thats an a.f.b carb. carter made a miiion of them,and i dont know how many variations thru the years on these early cars,plus they all pretty much look alike. so people,thru the years swapped them around to get a car to run. however,they made at least 10 different BASES!! ive done this my self. some work ok and some dont. the carb on your car might not be the right one,and might need a shim between the base and the first gasket in order for it to idle and run correctly. the auto places usually can get these for yor you.-------------the big screw in front allows extra air (only)thru the base for idle. the little screw on the choke cam does two things at the same time. it opens the choke butterfly(slowly) at the same time it opens the primaries a little bit for fuel mixture in conjungtion with the mixture screws. they all play a role together. its a pertty good carb considering their age.i still use them ,of course im a dinosaur.hope this helps cause im thoroughy confused lol,lol            richard king

[dcastine]

Thanks for the insight Richard!

I had the carb rebuilt last week and the rebuilder gave me a thin metal gasket that he said should be placed on the intake first, then the paper gasket, then the plastic spacer, another paper one, then the carb. I did this and she seems to run and idle just fine (albeit a little low for my taste). I'm running clean gas thru a new filter from an approved 2.5 Gallon container placed in front of the radiator. My tank needs to be taken down and the lines blown out - that'll get done during the upcoming weeks, but for now she's drivable and runs very well... I just wish I could bump up the idle just a tad.

Take good care!
-dc-

[Roger Zimmermann]

As far as I know, the metal plate is to be cemented to the carb base. Have a look in a shop manual.

Roger

[dcastine]

   Oh?   Okay thanks Roger, I will...

Thanks
Dave C