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Terry Harper

Up-draft carb issue

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So, we have been having a few issues. If the 1928 Lombard sets a few days. It will just crank and crank.

Unless we use the old trick of blocking the mouth of the carb with a hand  or piece of board.

 

Then it fires right up. The alternative is to use the priming cups and again it fires right up as well.

 

I remember my ex-father-in-law doing the hand trick with old Ford 8N tractors but I can't for the 

life of me remember or recall a solution to the problem.

 

The carb is a big Zenith 77

 

Thanks!

 

 

IMG_20190703_181551.thumb.jpg.de48c673d05633f007cfd2c2824b0484.jpg

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Does the choke plate not cover the intake hole enough to draw fuel?

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Virtually all updraft carburetors, when properly adjusted, require choke to start when cold.

 

Show me an engine with an updraft that starts well cold without choke, and I will show you a vehicle that gets less than efficient fuel economy.

 

Jon.

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Everyone that I ever spoke to about 26-32 Pontiacs said they were poor starters and couldn't be driven in the winter.  I never had any trouble with mine but the always needed full choke on the fist start of the day even right down to -45 degrees.  You had to be quick in opening the choke or it would flood.  It would even start with the hand crank at -40.

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Aand of course what everyone keeps forgetting is the fuels today are light years away from that available when those cars were built. The issue of having a starting mixture that's vaporizing enough when it's cold will always be a problem, there's little relevance in what happened when "Dad" owned the car back in the day.

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The choke is closed when we try to start. And yes you do need to be quick on the choke once it does fire-up.

Now to clarify: With the choke closed we still have to choke it with a hand or use the primer cups.

 

 

 

T

Edited by Terry Harper (see edit history)

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Sounds like the 40 Ford v8i had you had to kill it with the choke or it would not restart was a 6volt system and would sound like it was 12 volt.  Poor engine was flat worn out no compression. 

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Poor compression might be the actual culprit.

 

However, if the choke is functioning normally, I do not understand why placing one's hand over the air intake would make a difference.

 

Jon.

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As Jon said, poor compression can be a cause (lack of intake suction). And a weak, slow starter motor can also cause poor intake suction hard starting.

Also check,...

Float level. If too low that can cause hard starting.

Idle fuel circuit is not restricted with rust particles, and/or, crud. Being the smallest fuel passages in an updraft carb this is a common problem.

Idle circuit air leak causing too lean to start.

 

One other item. Most updraft carbs not only need full choke when engine is cold, they need the hand throttle cracked open a bit, also.

 

Paul

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This may be my first time I have an experience on a carburetor issue that doesn’t agree with Carbking.............

 

 

I have managed to set up ALL my early Cadillacs (1929-1931 8,12,&16)  without ever using the choke.......ever..........even in Massachusetts in November and December. Disclosure.......all my cars have very good compression and valves, and are set up and well sorted. Ed

Edited by edinmass (see edit history)
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Ed - I did say virtually all, not all (weaseling out ;) ) !

 

The Johnson's differ from what most would consider "conventional" updrafts in that they have a functioning accelerator pump with positive throttle activation, an extremely small primary air intake, and an auxiliary air valve (closed for starting).

 

There are a few other carburetors that often fit this criteria, such as the Schebler model S.

 

Jon.

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John......you were correct that the ones that don’t require choke get very poor fuel mileage! And the mixture control is terrible. We use to comment that pouring raw gas into the engine from an old boot would be a better fuel delivery device than a Cadillac Johnson carburetor.

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I have always had to choke when cold on anything updraft.  Occasionally, if hot I can not choke, but most of the time I choke some as most of the cars I have had are rather unforgiving and when hot you get one shot at it and muff it up and you will be sitting a while.  

 

Ed is right about the 31 Cadillac carb - I did choke when car had been sitting, but if it had run within a week I could start it without choking.

 

A good example is the Stromberg U-3 on the 1930 Franklin - I choked it every time I ran the car no matter cold or hot.   I had several carbs and swapped the butterfly around from the one with like a 95% solid butterfly (the 5% being a relief) to one butterfly that was 100% with a small spring loaded relief valve - I found that to be my favorite butterfly (probably because it was 100% closed to draw fuel but upon firing allowed it some air as needed while I was fumbling around at the controls). 

 

Also, not uncommon to turn an updraft car off and have it puddle gas out onto the ground - there is a lot of gas in suspension in the manifolds when an updraft car is running (most cars i have ever worked on or had there is some sort of drain that divers gasoline from puddling in engine pans). 

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10 hours ago, John_Mereness said:

I have always had to choke when cold on anything updraft.  Occasionally, if hot I can not choke, but most of the time I choke some as most of the cars I have had are rather unforgiving and when hot you get one shot at it and muff it up and you will be sitting a while.  

 

Ed is right about the 31 Cadillac carb - I did choke when car had been sitting, but if it had run within a week I could start it without choking.

 

A good example is the Stromberg U-3 on the 1930 Franklin - I choked it every time I ran the car no matter cold or hot.   I had several carbs and swapped the butterfly around from the one with like a 95% solid butterfly (the 5% being a relief) to one butterfly that was 100% with a small spring loaded relief valve - I found that to be my favorite butterfly (probably because it was 100% closed to draw fuel but upon firing allowed it some air as needed while I was fumbling around at the controls). 

 

Also, not uncommon to turn an updraft car off and have it puddle gas out onto the ground - there is a lot of gas in suspension in the manifolds when an updraft car is running (most cars i have ever worked on or had there is some sort of drain that divers gasoline from puddling in engine pans). 

The U-3 is a bit on the large side for that CID. With a cold engine, it needs the hand throttle opened about 1/4 of the way and  pull  full choke so that it is nearly flooding to start. But, the instant the engine fires the choke handle must be quickly pushed in about 3/4 of the way.

 

The 29 135 motor is the same CID but uses a smaller Venturi carb. It starts  more easily and is more responsive at lower RPM than the U-3 equipped engines. 

 

Franklin issued a service bulletin to address the flooding problem on 1930 when the engine started and owners were slow to get the choke open. The recommendation was to cut off about a 1/4 inch of the bottom of the choke plate. Some of those modified choke plates still show up. However, not being able to fully choke the motor, that modification to prevent flooding just made starting tougher. Solved one problem and added another.

 

In 31 Franklin went to using U-3's with choke plates that have a poppet valve. That allowed full choke, but when the intake suction became too great and risked flooding then the valve opened to bleed off some of the suction. It worked well and the poppet valve was used on the later carbs.  

 

Paul 

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12 hours ago, PFitz said:

 

In 31 Franklin went to using U-3's with choke plates that have a poppet valve. That allowed full choke, but when the intake suction became too great and risked flooding then the valve opened to bleed off some of the suction. It worked well and the poppet valve was used on the later carbs.  

 

Paul 

Paul, that was my favorite butterfly / Choke Plate = the one with the poppet valve (made car much easier to run)

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21 hours ago, John_Mereness said:

Paul, that was my favorite butterfly / Choke Plate = the one with the poppet valve (made car much easier to run)

John, your not alone. Around that time, Stromberg switched other model carbs over to that poppet type choke plate, including some smaller model updrafts. And I've seen it used on Zenith updrafts.

 

Paul

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I have a Carter updraft car by, and at first use of the day, I use full choke and part hand throttle. A few turns, I then reduce choke and the next turn, it starts. Throttle then goes in to adjust revs, until warm, then all way off . Phil.

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My 29 and 28 Hudson , same as above 

full retard , 1/4 throttle , full choke , 3 crank revolutions, push choke in half way and it starts every time when the choke is at the half way mark. Has been like that on the 29 for the 30 years if had it and for 25 years before that that my dad had it. 
every single time. But ... when it doesn’t it’s  time to check the points or battery terminals and connections.  

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On 10/19/2019 at 10:12 AM, carbking said:

Ed - I did say virtually all, not all (weaseling out ;) ) !

 

The Johnson's differ from what most would consider "conventional" updrafts in that they have a functioning accelerator pump with positive throttle activation, an extremely small primary air intake, and an auxiliary air valve (closed for starting).

 

There are a few other carburetors that often fit this criteria, such as the Schebler model S.

 

Jon.


yep my cad doesn’t need choke to start, it fires within a second and if it’s been running it starts the second you touch the starter 

 

it also leaks fuel like crazy when stopped (tank is still pressurised) but given they literally put a drain under the carb I suspect it always did. I wonder if I could put a catch can on the end of the drains to stop it going on the ground

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