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Old 06-21-2019, 08:17 AM   #1
Youngblood
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Default Dies at idle... Help

Hi; I have a 1930 town sedan running a touring motor built by Ron Kelly 3 years ago with a Snyder's high compression head. I am running a Model B Carb with a bored out Model A intake and it has run fine up to now. The car starts, idles and runs fine when cold. When the car warms up to temp (about 180 degrees at the top of the radiator) it still runs fine with plenty of power but when I let the car idle down, it runs for about 20 seconds and then starts to miss and dies.

I have checked the gas flow and it is good. I have cleaned the carb and tried a different idle jet and verified the comp jet is ok (no change). I have tried adjusting the air idle screw and think I have that set correctly. I replaced the spark plugs and they are gapped at 32. I have shot temperatures of the carb and it is about 150 degrees at the bowl. It seems that there is something wrong in the idle circuit but I can't find anything.

Can the gas be boiling at idle? Could a bad coil cause this? Any help is appreciated.
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Old 06-21-2019, 08:45 AM   #2
bigd1101
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Default Re: Dies at idle... Help

Check your intake manifold gasket. See if the bolts are loose. If not spray some carb cleaner around the gasket while running and see if the idle changes. If it does you have a leak.





Don
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Old 06-21-2019, 08:54 AM   #3
100IH
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Default Re: Dies at idle... Help

What you have now is a "divide and verify " with tests. Your assumption fuel or ignition is a good start. How can you see the floatbowl and know that the fuel level is being maintained with adequate flow. If you had one of the U shape level gauges, that would work. Have you seen the inline spark tools known as a noid lite. It will blink with each spark pulse. Can be put in series with the coil wire or at one of the plugs. These are tests that will lead you in the right direction and will avoid ordering parts that are not even related. Sometimes one can save time by substituting a known good part that"s OK. Think this through and find the answer to your original question. The best question is how can I test the ignition or fuel for my symptom.

Last edited by 100IH; 06-21-2019 at 09:00 AM.
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Old 06-21-2019, 09:17 AM   #4
30 Closed Cab PU
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Default Re: Dies at idle... Help

Sounds electrical to me, something heating up. You can try swapping in known good parts, or do a little troubleshooting.

If you do not have one purchase an ignition tester that plugs in series with distributor High Tension (outout) lead. I use this one, allow you to acually see the spark when the motor is running. Should tell you if the issue is electrical or carb/fuel.

https://www.snydersantiqueauto.com/P...earchByKeyword

Once it is doing it, meter the coil. Resistance across the terminals should be about 1.5 ohms for a 6 v coil, about 3 ohms for a 12 v coil. From each terminal to the center high tension distributor output, should be 5 - 20 k ohms. Or If you have a spare coil swap it.


Swap in a good known condenser.

Check the points gap, and ignition connections.

If fuel supply issues. Insure there is no dip downwards back towards the fire wall in the fuel line from sediment bowl to the carb. I've also heard adding a little Marvel Mystery oil to the gas can help. And have heard that clipping wooden clothes line pins to the gas line helps. Clean all gas filters - sediment bowl, carb, pencil shutoff filter.
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Old 06-21-2019, 10:14 AM   #5
ryanheacox
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Default Re: Dies at idle... Help

The only things that can heat up and cause issues in the ignition system are the coil and condenser. If you follow the advice in reply #4 that should point you in the right direction.


If the problem is fuel related though, can you keep it idling by giving it some choke? How hot is it where you are?
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Old 06-21-2019, 04:52 PM   #6
Mulletwagon
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Default Re: Dies at idle... Help

Had exact same problem which turned out to be a leaky inlet valve in the carb. Tell tale sign was the carb looked wet and would drip slightly when the engine was shut off.
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Old 06-21-2019, 05:44 PM   #7
Jacksonlll
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Default Re: Dies at idle... Help

You have an intake air leak. Check three places. Attachment to engine, attachment to carb, and the manifold itself.
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Old 06-21-2019, 09:39 PM   #8
jm29henry
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Default Re: Dies at idle... Help

what Jackson say make good scene
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Old 06-22-2019, 07:03 AM   #9
larrys40
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Default Re: Dies at idle... Help

Quote:
Originally Posted by Jacksonlll View Post
You have an intake air leak. Check three places. Attachment to engine, attachment to carb, and the manifold itself.
I agree it is most probable. Check carb bolts and intake exhaust gasket. Replacement is probably in order. Surface manifold if possible. Check rubber vacuum line for wiper . Plug manifold with 1/8 pipe plug if need be to isolate.
Larry shepard
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Old 07-03-2019, 11:02 AM   #10
Youngblood
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Default Re: Dies at idle... Help

Thanks to all who replied to my post. My problem was two fold. I checked the Ohm reading across the Coil and it was only 1.0 Ohms. It should have been 1.5 Ohms for my 6 volt system. Also, the Manifold gasket had a small leak at the intake for Number 3 and 4 cylinders. I changed the coil and Manifold gasket and the problem was solved.

Mike
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Old 07-03-2019, 01:05 PM   #11
30 Closed Cab PU
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Default Re: Dies at idle... Help

1.5 ohms for a 6v coil and 3 ohms for a 12v coil are "about" #s. However 1 ohm is definitely low.
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Old 07-03-2019, 10:13 PM   #12
Penthode
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Default Re: Dies at idle... Help

Have you checked the carburetor "secret passage" between the idle screw and the carburetor throat? There is a small hole in the throat immediately above the throttle flap which is the idle passage. I had the same symptoms as you. After checking pretty well everything else, I removed the top section of the Zenith and removed the throttle flap and idle screw and then poked a straightened small paperclip wire down the hole to clean out the crud from the passage way. You should be able to easily poke it from the throat diagonally until you can see the end from where the idle screw fits.

This passage is easily overlooked and because it conveys the idle fuel air mix and not just fuel, it tends to get blocked.

Once the passage was cleared and my Zenith reassembled, my car was transformed.
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