Author Topic: 1955 Cadillac fuel pump push rod tapping  (Read 304 times)

Offline 1966Eldorado

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  • Name: Tommy Statham
1955 Cadillac fuel pump push rod tapping
« on: September 29, 2017, 12:43:40 PM »
Backstory- first time driving my "55 greater than 25 mph.  I push down top open on my dual carbs.  The carbs stick open and I turn into Mr. Toads wild ride. I cut the car off while running wide open. Turns out that the threaded rod fell into the carb closest to firewall.  Now there is a rhythmic ticking from the engine. Wood stick to ear test makes it sound like fuel pump push rod. Car seems to have plenty of power and no other issues. except the ticking loud enough to hear from drivers seat. Raise idle the ticking speeds up, etc..

Any thoughts before I change the fuel pump and push rod? Could to be oil pump or something? Engine was Cadillac quiet before turning off while wide open ride
Tommy Statham
CLC# 28310
1966 Eldorado
1955 Coupe 2x4bbl
2011 Mercedes Wagon

Offline Steve Passmore

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #1 on: September 29, 2017, 01:34:46 PM »
Looking at the worst case scenario as you said something fell into the carb, Did anything else fall and get lost in there and it's now embedded into a piston smacking the cylinder head?
Had this problem on a car when I worked in a shop in the 60s. A small bolt had found its way into the engine and was pounded into the piston making a tapping sound.
Steve

Offline 1966Eldorado

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #2 on: September 29, 2017, 01:47:55 PM »
the threaded rod that the wingnut attaches to the carb didn't appear to have anything on it.  The sound doesn't change. Wouldn't it if something was bouncing around?
Tommy Statham
CLC# 28310
1966 Eldorado
1955 Coupe 2x4bbl
2011 Mercedes Wagon

Offline 1966Eldorado

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #3 on: September 29, 2017, 01:50:37 PM »
your key word was embedded. It was instant with no change since
Tommy Statham
CLC# 28310
1966 Eldorado
1955 Coupe 2x4bbl
2011 Mercedes Wagon

Re: 1955 Cadillac fuel pump push rod tapping
« Reply #4 on: September 29, 2017, 03:55:58 PM »
If a washer or something got into one of the combustion chambers, it will get pounded into the top of the piston.  At high speeds, the crown of the piston can rise up a bit and the thing could do more damage.

I'd use a borescope to find it and then probably remove the head and dig it out of the piston.  New headgaskets and a valve job too...
Art Gardner


1955 S60 Fleetwood sedan

Online Ralph Messina CLC 4937

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #5 on: September 29, 2017, 06:35:42 PM »
Tommy,

If I understand your description, the threaded rod you’re referring to is the one that the air breather fits over. The breather is then held  in place by a wing nut or star / round shaped knob. Do the wing nuts or knobs have washers under them, and if so, are both washers (front and rear carb) accounted for? Did you retrieve the rod from the carb throat?  If it was short enough to fall completely into the manifold, it may be laying in an intake passage and rattling when the valve is activated. I doubt that the ¼”rod can make its way passed the valve into the combustion chamber. I would try the bore scope suggestion above in each  manifold runner first. If they're clear pull the plugs and check each cylinder.

Ralph
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Offline cadman56

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #6 on: September 30, 2017, 07:46:28 AM »
A simple test would be to remove the fuel pump and start the engine?  When I ordered my fuel pump repair kit from Terrill Machine Felz advised the spring that holds the arm down on the push rod gets weak and that is when the tap starts.  If your engine runs fine I would start there.  Art makes a great suggestion about the bore scope too.
Good luck.
1956 Cadillac Coupe deVille (sold)
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Offline Steve Passmore

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #7 on: September 30, 2017, 08:50:31 AM »
your key word was embedded. It was instant with no change since

That's exactly what happened to me way back. The item does not bounce around, it gets embedded in the alloy piston and hits the cylinder head every stroke causing a tap.  The nut in my experience was a 3/16" and passed by the valve with ease. I sincerely hope that's not your problem. Just giving you the worst case as it seems a coincidence.
Steve

Offline 1966Eldorado

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #8 on: November 11, 2017, 05:19:02 AM »
Update
Jay Friedman came over. We used a stethoscope to pin point the sound is coming form fuel pump area. We changed fuel pump and push rod. The sound remains the same and in the same location.
Could this freak thing have effected a loeb on camshaft or is the harmonic balancer damaged from the sudden stop at wide open?
Tommy Statham
CLC# 28310
1966 Eldorado
1955 Coupe 2x4bbl
2011 Mercedes Wagon

Offline The Tassie Devil(le)

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #9 on: November 11, 2017, 05:26:38 AM »
......Could this freak thing have effected a loeb on camshaft or is the harmonic balancer damaged from the sudden stop at wide open? 
In a word, NO.   A sudden stop from wide open throttle, and I mean a really sudden stop, would probably break the crankshaft, as nothing could stand such a sudden stop, as in going from high revs to stop within a millisecond.   The Harmonic Balancer would have destroyed itself in the process.

I think all your engine would have done is simply wound down to zero revs, a bit like simply turning the ignition off.

Bruce. >:D
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Offline fishnjim

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #10 on: November 11, 2017, 09:28:29 AM »
If the cam lobe for fuel pump is wiped, the new parts still won't be tight enough.   There should be a
measurement in the service manual to see how much travel is normal.  I'd double check the rod dimension to make sure it's correct length.   Make sure the pump arm was installed correctly.
I'd take the valve covers off and look for a push rod that's loose or not moving like all the others.   It's also possible you threw a push rod, dished a lifter, or one's stuck from revving so high.   It's the same tapping noise you get from anything that's activated by the camshaft. 

Offline lexi

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #11 on: November 11, 2017, 11:07:28 AM »
The push rod length for a 1955 Cadillac is said to be 7.1425" - 7.1475" long, with a diameter of .4355" - .4360", (having a stroke of .245" - .250"), according to the 1955 Cadillac Shop Manual Supplement . Clay/Lexi

Offline 1966Eldorado

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #12 on: November 11, 2017, 11:57:14 AM »
Thanks everyone. To clarify I turned the ignition over with carbs stuck wide open. It runs fine except the in time tapping. We have house guests with three boys from 2.5 to 6 yrs. I will report back next week. Thanks for your time and wisdom
Tommy Statham
CLC# 28310
1966 Eldorado
1955 Coupe 2x4bbl
2011 Mercedes Wagon

Offline Jeff Rose CLC #28373

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #13 on: November 11, 2017, 03:01:22 PM »
Is it tapping every revolutuon or every other? Mite help you determine where it is.
Will the engine run slowly? If so, hook up a timing light to any plug and run it slowly. If you get a tap with every flash then it is up top. If you get a flash/tap, flash, flash/tap then you may have something in a cylinder.

Jeff
« Last Edit: November 11, 2017, 03:03:38 PM by Jeff Rose CLC #28373 »
Jeff
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Offline walt chomosh #23510

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Re: 1955 Cadillac fuel pump push rod tapping
« Reply #14 on: November 11, 2017, 03:27:59 PM »
hi guys!
  I had an air cleaner nut fall once into a motor (289 Ford) and ran the motor with the spark plug out in an attempt to clear the cylinder. I like Art's stethoscope thoughts though and would give it a try. Most auto repair shops nowdays should have a scope and it shouldn't cost much for them to have a look....walt...tulsa,ok