29 cadillac running poorly as the weather has cooled

[BillhymerMD]

Since the weather cooled my 29 Cadillac is running poorly.  The engine ran great all summer when it reached an engine temp 170 -185F.  Now the engine only reaches a temp of 140 - 155F and the engine has been flooding, car backfiring and all around running terribly.  The car has an electric fuel pump with fuel regulator placed many years ago, regulator set at lowest setting.  I placed another inline fuel regulator thinking too much fuel was the problem because the car was puking it all over the road but I still have the problem even though I've limited the fuel significantly from the pump.  Maybe it's the fuel?  Or perhaps its because the thermostatic controller isn't working to heat the engine up?  Any ideas appreciated.  

[nickelroadster]

First thing that comes to mind is that your float needle and seat are not working properly.  I don't think the temperature will make something like that happen.  I would check your float level also.

Edited November 26, 2016 by nickelroadster
addition (see edit history)

[Spinneyhill]

Sounds like what happens when a spec of dust or dirt or rust gets between the float needle and seat -> continuous flooding. Excessive cooling by too much fuel. It dribbles out everywhere too.

[cahartley]

I never heard of a thermostat getting stuck closed.

Start there.

[Grimy]

Doesn't this car have shutters operated by a thermostat?  All those Sylphon 'stats I've seen are 160*.

[hchris]

4 hours ago, BillhymerMD said:

Since the weather cooled my 29 Cadillac is running poorly.  The engine ran great all summer when it reached an engine temp 170 -185F.  Now the engine only reaches a temp of 140 - 155F and the engine has been flooding, car backfiring and all around running terribly.  The car has an electric fuel pump with fuel regulator placed many years ago, regulator set at lowest setting.  I placed another inline fuel regulator thinking too much fuel was the problem because the car was puking it all over the road but I still have the problem even though I've limited the fuel significantly from the pump.  Maybe it's the fuel?  Or perhaps its because the thermostatic controller isn't working to heat the engine up?  Any ideas appreciated.  

 

A  few thoughts, not in any particular order:

• are you using premium fuel ?
• having just changed seasons; fuel companies switch blends for summer to winter, so its possible you may have the last of a summer blend which wont atomise thru the carb now that the air temps have dropped.
• get some more heat into the engine, even if you resort temporarily to blanking off the lower half of the radiator
• if you have a carb/manifold heat valve make sure its working properly

 

[Spinneyhill]

I would have thought the manifold heat valve was irrelevant to cool running. It is only meant to warm the carb. to stop icing in the venturi.

 

Did all these bad things start happening at the same time? i.e. one problem or several.

[Restorer32]

Those early Cadillac carbs can be very frustrating.

[Jim Bourque]

I have the same issues with my 1928 341A when the gasoline changes to the winter blend. The point at which the fuel boils is much lower in the winter blend. 

The Cadillac V8 is very sensitive to this due to the carb sitting between the exhaust manifolds. My work around is to stock pile enough summer fuel to get me through fall and early spring. 

 

Check out Reid Vapor Point Arizona on the Internet for more info 

 

i would also also recommend disconnecting the 2 carb heat pipes rom the exhaust manifolds to the intake manifold.

 

Jim

 

[BillhymerMD]

Thanks for all the info.  I'll have a look at the float and see if I can't work through the issue.  Not a lot I can about the fuel.  

[hchris]

20 hours ago, Spinneyhill said:

I would have thought the manifold heat valve was irrelevant to cool running. It is only meant to warm the carb. to stop icing in the venturi.

 

Did all these bad things start happening at the same time? i.e. one problem or several.

 

The manifold heat valve promotes a better atomising process during cold running; if its stuck in the open position there is no heating of the manifold, fuel condenses and pools on the cold induction manifold walls and doesn't reach the combustion chamber in an atomised form, the net result is poor running and flooding.

 

As to icing in the venturi, you need a source of warm air entering the carb intake to prevent this, the manifold heat valve is below the venturi.

[hchris]

14 hours ago, BillhymerMD said:

Thanks for all the info.  I'll have a look at the float and see if I can't work through the issue.  Not a lot I can about the fuel.  

 

About the fuel, the higher octane rating you have the better it will atomise; yes amongst other things the reid vapour pressure is all about how well certain fuels perform at different ambient temperatures. When its available spend the money and always go with the highest rated fuels, you might be surprised at the difference in running.

[Alfre]

Get the water temp up to 160 or above.

Al

[JFranklin]

Try a 180 degree thermostat and try carb adjustment, and new gasoline before you go to the trouble of opening up that carb.

[hidden_hunter]

13 hours ago, hchris said:

 

The manifold heat valve promotes a better atomising process during cold running; if its stuck in the open position there is no heating of the manifold, fuel condenses and pools on the cold induction manifold walls and doesn't reach the combustion chamber in an atomised form, the net result is poor running and flooding.

 

As to icing in the venturi, you need a source of warm air entering the carb intake to prevent this, the manifold heat valve is below the venturi.

 

Does it really need the manifold heat with modern gas? 

[Jim Bourque]

In the 1920's gas was closer to kerosene. That's why carbs/intake manifolds were heated, the heat vaporized the gas. Today's gas does not need or want the heat.

 

As far as carb icing in Phoenix AZ, I doubt there is enough moisture in the air for that to be a problem.

 

As another poster on these forums says "90% of carb problems are ingnition related".... verify your ingnition system is working as it should, you may have more than one issue. 

 

I am not a fan of electric fuel pumps on carbs that were designed to run a vacuum fuel pump, especially on a carb as finicky as the Johnson/Cadillac. If you need parts for your carb, Classics and Exotics has Viton tipped needle and seat, gaskets and a modern material float that are top quality. If you are not comfortable rebuilding your carb, they can do it for you.

 

I hope you get that beautiful classic back on the road soon

 

Jim

[hchris]

3 hours ago, hidden_hunter said:

 

Does it really need the manifold heat with modern gas? 

 

Absolutely, the properties of todays gas are designed to function under high pressure for injection systems. Essentially the fuel is properly atomised in the region of 80psi and sprayed into the cylinder thru precision orifice nozzles.

 

A carb atomises fuel thru the low pressure area of the venturi just above the throttle plate, nowhere near as effective as a high pressure pump; the then (marginally atomised) fuel passes thru a convoluted, and this case cold, manifold before getting to the cylinders, along the way the cold fuel in contact with a cold manifold turns back to liquid and sticks to the walls of the manifold. Hence flooding and poor running are the usual characteristics. So in this instance manifold heating is desirable, up to a point.

 

Of course the down side of our primitive manifold heat mechanisms is during the summer, where they become too effective and over atomise - read vaporise - the fuel and we suffer from vapor lock, this is I suppose the price to pay running old cars on modern fuels.

[hidden_hunter]

10 minutes ago, hchris said:

 

Absolutely, the properties of todays gas are designed to function under high pressure for injection systems. Essentially the fuel is properly atomised in the region of 80psi and sprayed into the cylinder thru precision orifice nozzles.

 

A carb atomises fuel thru the low pressure area of the venturi just above the throttle plate, nowhere near as effective as a high pressure pump; the then (marginally atomised) fuel passes thru a convoluted, and this case cold, manifold before getting to the cylinders, along the way the cold fuel in contact with a cold manifold turns back to liquid and sticks to the walls of the manifold. Hence flooding and poor running are the usual characteristics. So in this instance manifold heating is desirable, up to a point.

 

Of course the down side of our primitive manifold heat mechanisms is during the summer, where they become too effective and over atomise - read vaporise - the fuel and we suffer from vapor lock, this is I suppose the price to pay running old cars on modern fuels.

 

Interesting, it's pretty common the buick scene to remove it, guess I'll leave it on my 22 and see how it goes. Don't think I'll want to do too much driving when it's 110 out

[hchris]

2 hours ago, Jim Bourque said:

2 hours ago, Jim Bourque said:

In the 1920's gas was closer to kerosene. That's why carbs/intake manifolds were heated, the heat vaporized the gas. Today's gas does not need or want the heat.

 

As far as carb icing in Phoenix AZ, I doubt there is enough moisture in the air for that to be a problem.

 

As another poster on these forums says "90% of carb problems are ingnition related".... verify your ingnition system is working as it should, you may have more than one issue. 

 

I am not a fan of electric fuel pumps on carbs that were designed to run a vacuum fuel pump, especially on a carb as finicky as the Johnson/Cadillac. If you need parts for your carb, Classics and Exotics has Viton tipped needle and seat, gaskets and a modern material float that are top quality. If you are not comfortable rebuilding your carb, they can do it for you.

 

I hope you get that beautiful classic back on the road soon

 

Jim

In the 1920's gas was closer to kerosene. That's why carbs/intake manifolds were heated, the heat vaporized the gas. Today's gas does not need or want the heat.

 

As far as carb icing in Phoenix AZ, I doubt there is enough moisture in the air for that to be a problem.

 

As another poster on these forums says "90% of carb problems are ingnition related".... verify your ingnition system is working as it should, you may have more than one issue. 

 

I am not a fan of electric fuel pumps on carbs that were designed to run a vacuum fuel pump, especially on a carb as finicky as the Johnson/Cadillac. If you need parts for your carb, Classics and Exotics has Viton tipped needle and seat, gaskets and a modern material float that are top quality. If you are not comfortable rebuilding your carb, they can do it for you.

 

I hope you get that beautiful classic back on the road soon

 

Jim

 

Where I live its recognised as the driest state in the driest continent on this planet, I can assure you that in the middle of winter I suffer occasionally from throttle ice.

 

I wouldn't discount ignition or any other problems for that matter, but if I was suspecting fuel the above posting explains the probabilities.

[hchris]

3 minutes ago, hidden_hunter said:

 

Interesting, it's pretty common the buick scene to remove it, guess I'll leave it on my 22 and see how it goes. Don't think I'll want to do too much driving when it's 110 out

 

Yes as I said it cuts both ways, manifold heat is a pain in summer but an asset in winter. I guess if nothing else this discussion highlights an often not understood aspect of todays fuel issues with our older cars.

 

Just as an aside, if you really need to raise your awareness of cold weather piston engine fuel issues, open up a manual for light aircraft pilots; probably one of the most common causes of aviation mishaps is throttle icing, summer and winter.

[Ovalrace25]

I need to keep this short.. Lost my Dad this week. But am trying to take a break and see what has been going on in the car world that he and I shared since I was a 4-year old kid when he put me in my first 1/4 midget.

OK, since I have plenty of under hood experience with the 341 engines and Johnson carbs, I'm going to agree with a lot of what I read here. The Johnson HATES any pressure to it. adjustable regulators and electric pumps can lead to a disaster. Vapor Lock is a huge factor. This gas eats up rubber products not approved for fuel injection engines and modern gas. THINK ABOUT how vapor lock was dealt with in the 60's on Air Conditioned cars....  RETURN LINE-------  THERE, I GAVE YOU THE CLUE, NOW FIGURE IT OUT.. I have to get back to my family...

[C Carl]

OH , Rod , so sorry to read this. Man , I just noticed your posting of a few minutes ago , brought it up and what a shock. I am glad I had the pleasure of meeting your dad , and having had the opportunity to put a car lovers smile on his face with the old Cadillac. Deepest sympathy , friend. You and Cindy are among the very finest people I have ever met. Please call me when it feels right to you. -  Carl

[Guest]

On ‎11‎/‎27‎/‎2016 at 2:20 PM, JFranklin said:

Try a 180 degree thermostat and try carb adjustment, and new gasoline before you go to the trouble of opening up that carb.

There is no thermostat in the normal sense. There is a "shutterstat" in the top radiator tank that controls the opening of louvers (shutters) in front of the radiator core. I doubt if that has anything to do with his problem. The shutterstat is often inoperative on these cars, and since replacement requires removal of the grille shell, they are often found wired open.

 Also I agree with those that have mentioned that electric fuel pumps and regulators are a mistake with these carbs. I don't care how low you have the pressure set, these carbs were designed for gravity flow. Ditch the electric pump. Block off the exhaust crossovers with steel plates, disassemble and clean the vacuum tank and lightly oil the valves in the lid. Reassemble with new gaskets and make sure there are no cracks in the pot metal lid. Rebuild the carb or have Classic & Exotic do it.

Edited December 8, 2016 by Guest (see edit history)

[junkyardjeff]

Does it run bad the whole time its running and even after its warmed up as much as it can,I have a couple cars that the carb will ice up and idle rough until the carb warms up and then its fine.

[lump]

BillhymerMD, 

You are getting lots of great advice here. I'll offer a suggestion of something to check that is totally different, but resulted in similar type symptoms for my 1923 Hupmobile. 

 

Do you have an inline fuel filter? (Preferably a clear one, so you can check it visually). 

 

Like you, I have an electric fuel pump with a pressure regulator dialed down as low as possible. And over many years we have enjoyed driving our reliable car around all over the place. But then suddenly it would start running poorly, with symptoms similar to those you described. Long story short, we found dirt/rust in carb bowl, which was interfering with needle and seat, causing fuel puking, poor performance, etc. We tried everything to solve the problem, but all fixes were just temporary. Removed fuel tank, coated it inside, etc, etc, etc, etc. And it would be great for a few months, and then the problem would return. Upon examination we found the fuel filter full of crap again, with the problem returned. Eventually we fabricated a brand new gas tank out of stainless steel, and replaced or rebuilt all components in the fuel system. Problem solved...permanently. 

 

Of course this may have nothing to do with your issue. But the symptoms were similar, so I offer my experiences. Good luck!