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1947 Cadillac Accelerator pump

Started by bill_boos, September 05, 2020, 05:16:42 PM

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bill_boos

At idle, if I step on gas gently it will accelerate smoothly. If I step on it harder, it will hesitate like it is going to stall and will sometimes cough or produce a small backfire.
I know on some models there are two adjustment holes on the accelerator pump rod. Does the '47 have rod adjustments. If so, where are they on the carburetor. If symptom sounds like something else, I'd appreciate your opinion based on your knowledge or experience.

Thanks, Bill
2013 SL 550
2006 Bentley GT Continental
2003 CL 600
1947 Lincoln Continental Cabriolet
1949 Cadillac Sedan (sold years ago)
1956 Cadillac Convertible (sold)
1947 Cadillac Sedanette (Just Bought Oct 2019)

fishnjim

Before doing unnecessary surgery, I'd check the timing and associated ignition parts.  aircleaner, etc.
Also, possible don't step on it hard...    I don't think they were known for speed or holeshots.

signart

#2
Squirt some light oil (like 3 in 1) down the pump shaft, wait a little while then shoot some more. Then take it for a drive and give it some hard throttle. This is a temporary fix if it works, but most importantly will help diagnose a bad pump seal. 
I wouldn't adjust anything before trying this.
Art D. Woody

bill_boos

Art, thanks. Can you describe where the pump shaft is located on my carburetor or is your answer based on accelerator pumps in general.
2013 SL 550
2006 Bentley GT Continental
2003 CL 600
1947 Lincoln Continental Cabriolet
1949 Cadillac Sedan (sold years ago)
1956 Cadillac Convertible (sold)
1947 Cadillac Sedanette (Just Bought Oct 2019)

signart

Not familiar with your particular carb, but most work the same. The shaft will plunge into the bowl at some point as in the red circle.
Art D. Woody

Alan Harris CLC#1513

Many carburetor problems turn out to be ignition related. A backfire or a hiccup makes me think ignition.

If you pump the pedal with the car not running, do you get a spurt of fuel in the carburetor? If you do, your accelerator pump is working.

signart

#6
Not saying for certain the pump seal is the problem, but a worn seal will pump a stream of fuel at least once or twice if the bowl has not leaked down and a good seal will not pump fuel if the bowl is empty with engine off, at the same time one can't assume a pump seal is worn when the fuel bowl is not full.
Assuming it starts, runs and idles well with a classic flat spot off idle that could be timing or ignition or carb.
I like to start with the simple stuff before adjusting things. Takes less than a minute.
Art D. Woody

Daryl Chesterman

Have you checked the vacuum advance on the distributor to see that it is operating correctly?  A bad diaphragm in the vacuum advance will give the same symptoms as you are experiencing.  With the engine running and using a timing light, you can shine the light on the timing marks and see what happens to the timing when the vacuum advance is disconnected from its vacuum sourceâ€"timing will drop about 15 degrees.  Alternatively, you can use a hand vacuum pump, such as a MightyVac MV8000 (or similar), and connect it to the vacuum advance and pump it to 18 inches of vacuum and it should hold the vacuum.  If it doesn't, the diaphragm is bad and the advance unit will need to be replaced or rebuilt.  Another problem could be that the vacuum advance is not rotating the base plate in the distributor because it is binding for some reason.  This can be checked by removing the distributor cap and applying vacuum to the vacuum advance unit, watching to see if the base plate is rotating as vacuum is applied.

Daryl Chesterman

bill_boos

Quote from: signart on September 06, 2020, 02:03:26 PM
Squirt some light oil (like 3 in 1) down the pump shaft, wait a little while then shoot some more. Then take it for a drive and give it some hard throttle. This is a temporary fix if it works, but most importantly will help diagnose a bad pump seal. 
I wouldn't adjust anything before trying this.


Think I've found accelerator pump. There is a small housing on the front of Carter carb with small wire rod linkage going to it from accelerator rod. There is a cover with 2 screws. Instructions on the top say to "Oil Under Screws". I don't know if that means oil in housing body so it goes to the bottom or literally pour oil directly into screw holes. You may not have the same carb so someone else may chime in, I hope.
2013 SL 550
2006 Bentley GT Continental
2003 CL 600
1947 Lincoln Continental Cabriolet
1949 Cadillac Sedan (sold years ago)
1956 Cadillac Convertible (sold)
1947 Cadillac Sedanette (Just Bought Oct 2019)

signart

I see now you have a Carter WCD. If you want to try and oil the pump seal, which is leather if original, take the cover off after removing the two screws. You can work the linkage then and see the movement up and down of the plunger operating the pump. Oil this down the center of this mechanism that is operating up and down. Do not oil the screw holes by the way.
I don't know if replacement leather seals are still available, probably not. If it has been replaced with rubber or whatever, it's likely damaged by ethanol. Either way if the oil treatment improves acceleration, you are looking at replacement for long time service.
I've been known to drive some heaps where this was regular maintenance. ::)
Art D. Woody

bill_boos

Art, thanks once more for sharing your considerable knowledge. I'll try the oiling the seal. Are new pumps available or can seals be replaced? Is it a difficult job?

Do you know if Carter was OEM on the '47 or did they alternate with Stromberg. I have a 1942 Shop Manual that the cover indicate is for 1942- 1947 and it only refers to Stromberg. The manual is only about 200 pages and over 100 are on the Hydramatic.
Is there a better shop manual
2013 SL 550
2006 Bentley GT Continental
2003 CL 600
1947 Lincoln Continental Cabriolet
1949 Cadillac Sedan (sold years ago)
1956 Cadillac Convertible (sold)
1947 Cadillac Sedanette (Just Bought Oct 2019)

signart

According to my old Chilton's manual, Carter would be correct for all series '46-'48 Cadillac models.
Stromberg type AAV-26 would be correct also for series 60, 61, 62 and 75 Cadillacs '46-'48.
Don't know what series is left out of Stromberg, but I think Stromberg would be easier to work on. There are overhaul kits still available for both, but not all the parts of the carburetors are available new. So don't lose any clips or such when disassembling.

You said your car idles well I suppose. Does it start well once fuel is in the bowl after cranking? What about once you get past the initial flat spot, can you accelerate hard and then the engines runs out smoothly?
Art D. Woody

bill_boos

"Does it start well once fuel is in the bowl after cranking? What about once you get past the initial flat spot, can you accelerate hard and then the engines runs out smoothly?"

Starts without cranking -- about 2 seconds. Whether cold or warm, when idling, I can step on gas with a very light touch and it will rev smoothly. If I step on gas a little harder it will hesitate like it is going to stall, sometimes coughs then will smooth out. Yesterday with air cleaner off and hood open when it coughed I got a small backfire and a flash of flame I could see through the windshield.
When starting from a stop, same symptoms -- hesitation, then accelerates smoothly and strongly
2013 SL 550
2006 Bentley GT Continental
2003 CL 600
1947 Lincoln Continental Cabriolet
1949 Cadillac Sedan (sold years ago)
1956 Cadillac Convertible (sold)
1947 Cadillac Sedanette (Just Bought Oct 2019)

signart

#13
FYI Stromberg 97's, one of the most popular carbs of the era are being reproduced with modern improvements that should fit Cadillac assuming your Carter is 3 bolt base. Very similar to the looks of your Carter and the '46-'48 Stromberg, and unless you prefer nothing less than oem, you might consider this alternative if it comes down to it.
Speedway Motors offers one as a Stromberg 9super7 for about $280 with coupon. Saw a new reproduction on evilbay for $229 w/shipping. Check with them for application.

Still not saying for certain your circumstance related to an ignition, timing or fuel problem, but running as you describe sounds like a temporary lean condition. Hoping some oil would condition the leather seal and give some "stimulus" to the fuel delivery.

 
Art D. Woody