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Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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23,850 Posts
Are the plug tips getting black from carbon fouling? This may indicate a rich mixture. If the engine smoothes out by introducing a vacuum leak (added air) by pulling an intake manifold vacuum hose, it may be running rich.
If a shot of carb cleaner solvent mist over the carburetor while it's running seems to smooth it out, then the added mixture may indicate that it's running lean.
If the vehicle sat over the season or the inside of the fuel tank is contaminated with old fuel deposits, that could cause issues. If the fuel pump diaphragm and internal check valves were allowed to dry and then re-wetted with fuel, they may not pump or seal very well. If the diaphragm ruptures on an old pump, fuel can enter the crankcase and mix with the oil. You might smell this on the dipstick and the oil will be thin. Measured fuel pressure should be 3-7 psi. A fairly accurate means of checking the fuel pump is to have the hose end pump fuel into a clear plastic soda bottle. The pump has to move fuel upwards about 2 feet to the carb and you should see good spurts while cranking. Use safe practices when handling raw fuel with rags to soak up any spills and no open spark or flame in the vicinity.
Carburetors can be trouble as paper gaskets shrink when allowed to dry if the vehicle sits and won't seal well when re-wetted. Rubber o-rings harden and won't reseal when re-wetted.
RV's seem to be mainly affected by these kinds of fuel system problems because of sitting for periods of time with old fuel in them.
 

·
Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
Joined
·
23,850 Posts
Is there a vacuum hose routing diagram label still under the hood? It may have peeled off and blown away years ago. Is this the correct carburetor?
The m/cyl linkage bellcrank nut is a one-time use nut and I can't remember the last time that I serviced one of these. They can bind and I don't think that parts are easy to get for these anymore. You might try freeing it up with penetrant and oil. If not, disassembly may be the answer.
http://www.factorychryslerparts.com/showAssembly.aspx?ukey_assembly=544566&ukey_product=4280302
If you don't have a factory service manual, it may pay for itself quickly.
 
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