Troubleshooting drivability

[Jordan Johansen-Moe]

Hey everyone. Last year I had some trouble keeping the Caddy running. A little backstory, car hadn’t ran in 30 years. Rebuilt the crankshaft. I had it running pretty well for a bit. Even drove it the 20 miles to the Back to the 50’s car show and back. After that it had trouble staying running. It would die under moderate throttle and only idle for about 30 seconds before dying. I’ve decided to install an electric choke and block off the exhaust ports along with removing the heat raiser. Is there anything else anyone can think of the might help make troubleshooting easier?

[Dennis P. DiBari]

Hi Jordan,

     I won't be around tomorrow to follow up, but just a few thoughts about your 64 Sedan DeVille.  After rebuilding the crankshaft and eliminating the heat riser and taking care of the intake manifold, how old is the carburetor and or gas?  Mine was also dormant for 30 years.  If you have a Rochester 4 Barrel, does it have the two small mixture screws in front, along with the much bigger idle screw in the left rear of the carburetor?  I only ask because that large idle screw in the rear is key to it idling properly.  If you get no reaction to turning the screw in or out, the vacuum underneath the carburetor might be clogged from the PCV hose/plastic plate.  Someone put an improper top carburetor gasket on my 64 and it blocked the hole for the vacuum for that idle screw.  There has to be a small triangular cut out specifically for that top gasket for that carburetor.  Once the fast idle kicks down and choke is open, the large screw is adjusted first (turning counterclockwise increases the idle).  Subsequent to that, adjust the two mixture screws.  Just some thoughts?

Yours truly,

Dennis DiBari

Cottekill, NY  

  

[Dennis P. DiBari]

Jordan,

     One last thought.  How is the fuel pump on your Caddy?  If it is lagging, t hen the idle will be erratic as well.

Dennis DiBari

[Jordan Johansen-Moe]

Thanks for the reply, Dan. The fuel system is all new, from the tank all the way to the rebuilt carb. It is a Rochester, I’ll do some messing around with the idle and mixture screws. I did find that the float levels were a little bit off. So I adjusted those. Hopefully that’ll give me something to work with.

[C. Van Tune]

A contributing item might be our nemesis...modern gas with ethanol. It can add to a the tendency for older cars to idle rough (especially when hot) and vapor lock.  My first trouble shooting fix is to install an elective helper pump near the gas tank.

Then, make sure all your fuel lines are away from contact with great sources, and wrap the metal lines with insulation material.

Third, try to find a station with pure gasoline.  

Let us know what fixed your problem. 

[Dennis P. DiBari]

Jordan,

     C. Van Tune makes a salient point with the gasoline issue.  Here in NY, we have one gas station that carries 91 octane NON-ETHANOL gasoline.  This is the only gas I put in my 64 Caddy.  I also add an octane booster and Marvel Mystery oil at times to keep it smooth.  

Dennis DiBari