News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

49 Cad Running Rough

Started by FabCad, October 25, 2012, 02:31:10 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

FabCad

I'm experiencing sluggishness at mid to high RPMs and having trouble pinpointing the problem. The car idles great and runs smooth at lower speeds, but when I step on the gas, it hesitates and chokes. Somebody suggested low fuel pressure could be the cause... Does that sound like a likely culprit, or are there other possibilities? 

For some background, here's what I've done so far:
1. Cleaned out gas tank, all new fuel lines
2. Rebuilt fuel pump
3. Rebuilt carburetor, professionally tuned
4. Full tune up: points, plugs, cap, wires, rotor, condenser, coil
5. Timing set
6. Fresh fluids

Any advice is appreciated.
1948 Sedanette
1949 Convertible
1950 Convertible
1957 Biarritz
1960 Convertible

Jay Friedman

One possibility is the carburetor accelerator pump is not working right in spite of the rebuild.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."

Raymond919

Just a quick thought: vacuum leak someplace, vacuum advance not working or disconnected?

R Sotardi #11719

It could be a few things. One comes to mind; the accelerator pump in the Carb. Due to the modern fuels the small "plunger" type can deteriorate or swell. It will cause what you have, especially hesitate on rapid acceleration. Sometimes it will leak when "the throttle is punched". Did this occur before the rebuild? A bad advance unit in the distributor can cause poor acceleration response. The carb can load up and cause your issue. Fuel pressure can be checked with a gauge. Dirt can block a passage in the carb also. This can occur when a loose piece of dirt travels internally after a carb rebuild. Ron

R Sotardi #11719

Ray and Jay, beat me to it. Ron

FabCad

Thanks for the tips!  I'll check the carburetor accelerator pump and vacuum advance.
1948 Sedanette
1949 Convertible
1950 Convertible
1957 Biarritz
1960 Convertible

gary griffin

If you have checked all of the usual systems I would suspect the cam lobes to be worn. Since the government caused Zinc to be removed from oil to accomodate smog free exhaust systems older cars have had a lot of cam failures.

Read up on ZDDP, an oil additive to correct this problem. It wont fix a dmaged cam but it will protect replacement cams.
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver