Starting problems / carb problems

[Jesper Krog Jensen]

Hi All,
I would like to ask your help to solve some problems I am having with my 63 coupe de ville.

The problem is that when the engine is cold it's very hard to start the car. What I have found is that the choke valve does not close completely. It's only a millimeter or two but it seems to be enough to cause starting problems. When I close the choke valve by touching it gently, the car starts without problem.

Jason Edge says it sounds like a new heat riser is needed. So before I order this, I wonder if any of you have some ideas. Thank you all in advance.

[Dennis P. DiBari]

Hi Jesper,

     As David said, the slightest adjustment on the black spring cover can make all the difference in the world.  It took me a few tries when my 64 cooled down, but just a fraction of a turn to close it further will do it.  Let it warm up and see if the choke opens all the way and it kicks down to normal idle.  David was so right, be sure the parts are clean inside, as the black dirt can ruin the operation of the choke.

Dennis DiBari, Cottekill, NY

[David Thomas]

If I understand correctly, you said that when you gently pushed the choke valve closed the car started instantly and the car runs well after it starts. That being said, your problem sounds like a malfunctioning choke or maladjusted choke. Use carburetor spray to spray the choke valve shafts, plate and interior of the carburetor throat. Be sure there is no gum to cause sticking. Spray the linkage link pivots, the weighted fast idle cam pivot and the lever on the choke housing where it exits the body. Be sure all these parts are free of gum or dirt and they move without binding in any way. Place the carburetor spray tube at the edge of the hole where the choke plate shaft exits the carburetor body, spray cleaner in between the body and valve shaft. You should see spray exit inside the carburetor throat. Work cleaner in both sides and pivot the choke valve while spraying to work the cleaner down the shaft bearing surfaces. Take the black spring cover off the choke housing. Inspect the choke housing on the carburetor. Spray cleaner in the choke housing flushing out any gum or carbon. If the choke housing is all black and sooty, your choke tube in the manifold has failed and your car is sucking exhaust gas into the choke.

Bottom line, the choke parts have to be clean with no binding. If everything cleans up and looks good, put the black spring cover on the carburetor and place the index mark at the factory setting. If the choke valve does not close, turn the spring very slightly clockwise and try again. Do a trial and error adjustment until you can open the throttle and the choke valve closes just enough to touch the throat of the carburetor, blocking it off. To test the choke closing, open the throttle slightly while holding the choke wide open, then let the throttle close, then release the choke valve. At this point the throttle valves are seated in their bore and the choke is open. Push the throttle open a little, If the choke is properly adjusted, the choke valve should close just touching the primary throat of the carburetor.

Start the car and let it warm up. The choke valve should fully open after a few minutes. The old thermostatic springs can wear out or become inconsistant. If yours does not allow a consistant operation or will not adjust so the choke is servicable, you may need a new temperature spring.

Hope this makes sense! David

[Jason Edge]

As long as your cooling system is good it should keep the engine at normal temperature. I would expect your thermostat would stay open more as it would hit open temp quicker. The main point is all you LH exhaust is forced across the intake. The intake WOULD be hotter than normal after warmup. This would probably affect the carb performance also and could see a closed heat riser with extra heat under the carb causing vapor lock not to mentioned cracked intakes, premature decay of the choke tube through center intake exhaust port. I'm just saying its a simple item to check since it's either opening on heat up or not and you can simply take your hand and see if you can manually open, and can cause several issues including harder startup in very cold climates.

[Jesper Krog Jensen]

Thank you all for the help so far. Actually I changed the distributor cap, rotor and vacuum unit last year which improved the general running. It idles very stabile.

Jason, if the riser valve is not operating correctly (stay closed) would the temp of the engine then not be higher than normal ? The temp now stays super stabile.

Anyway I will check that the timing is correct, the riser valve is working, the vacuum tubes are in good shape and pull a spark plug to see how the mix looks.

Thank you all.

[Jason Edge]

If the timing is not set right the car can be hard to start.  Of course make sure all the ignition components such as distributor cap and rotor, and points are not corroded and points dwell is set correctly. I've had parts cars I've brought in and just swipe of some med sandpaper across the points gap and rotor and distributor contacts has been the difference between not cranking and canking.   Just to back up, I mis-read the original email you sent and thought you were saying your heat riser butterfly was sticking. That is something you want to check and make sure it opens all the way up once engine is at running temperature. If they are stuck open they can make stock setup cranking a bit harder, and if stuck closed will make engine run like crap once engine heats up and will force almost all left/driver side gases across that intake center exhaust port making the engine that much hotter. I have a good notion that sticking heat risers is one of the reasons we see all of these cracked intake manifolds. If you run a car 10,000 miles pushing all of the LH exhaust gase across the engine to and out the  RH exhaust manifold that is a lot of extra fire hot exhaust gas blasting at both the intake and RH exhaust manifold.  The heat riser is definitely one of the first things I check when trying to crank a parts car.

[Kurt]

I would also check the accelerator pump. To do this pull off the air cleaner (engine off) and move the carb linkage by hand (choke fully open). You should see 2 streams of liquid gasoline squirting into the primary barrels. My car had a similar problem that you describe. My choke tube was bad and my accelerator pump was bad. I ended up blocking off the hot air tube in the manifold & converting the carb to a manual choke. I also replaced the accelerator pump. I can now start it at any temperature with no problems.