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331 won't start after warmed up
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   Forward Look Technical Discussions -> Engine, Exhaust, Fuel and IgnitionMessage format
 
green monster
Posted 2022-10-06 8:57 PM (#624732)
Subject: 331 won't start after warmed up


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My hemi doesn't want to start after I warm it up (not overheated) and let it set for 5 minutes or so.

Let is cool for 30 minutes and no problem.

It starts fine when cold.

I can force it to start by giving it a shot of starting fluid.

When it starts it pings a second then runs like there's nothing wrong.

Carburetor is good and works well.

Point dwell checked and in spec.

Changed the coil, now I suspect it is the old condensor and have one coming.

Next possibility would be is to add a 12v bypass to the ballast resistor so the coil has 12V while cranking.

Anyone else have this kind of issue?

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Powerflite
Posted 2022-10-06 9:09 PM (#624734 - in reply to #624732)
Subject: Re: 331 won't start after warmed up



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If you can solve the problem with a shot of starting fluid, then the problem doesn't exist in your ignition system. It's a fuel issue. Most likely culprits are:

1. Excessive fuel evaporation inside the carb due to ethanol content. Try adding a phenolic spacer under the carb to reduce heat transfer.
2. Vapor lock in the fuel line. Figure out where the fuel line is getting too much heat, like next to an exhaust manifold or choke well.
3. Fuel pump is weak when hot. Replace or rebuild fuel pump.

Also, try increasing the ignition advance setting. This will make it run cooler and stronger too.
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green monster
Posted 2022-10-09 10:56 AM (#624798 - in reply to #624734)
Subject: Re: 331 won't start after warmed up


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Powerflite - 2022-10-06 8:09 PM

If you can solve the problem with a shot of starting fluid, then the problem doesn't exist in your ignition system. It's a fuel issue. Most likely culprits are:

1. Excessive fuel evaporation inside the carb due to ethanol content. Try adding a phenolic spacer under the carb to reduce heat transfer.
2. Vapor lock in the fuel line. Figure out where the fuel line is getting too much heat, like next to an exhaust manifold or choke well.
3. Fuel pump is weak when hot. Replace or rebuild fuel pump.

It has a new electric fuel pump, so I doubt fuel.
I forgot to mention that when I checked the dwell, it would not start with the alligator clip on the new coil neg. screw.
I take the clip off the coil and it would start up.

Also, try increasing the ignition advance setting. This will make it run cooler and stronger too.
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57chizler
Posted 2022-10-09 3:47 PM (#624805 - in reply to #624732)
Subject: RE: 331 won't start after warmed up



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Does the engine turn over on the starter as briskly when warm as it does when cold?
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Shep
Posted 2022-10-10 12:32 PM (#624821 - in reply to #624805)
Subject: Re: 331 won't start after warmed up



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My 55 New Yorker did this in hot weather. Rerouted the fuel lines away from the hot areas on the engine. Made sure the heat riser worked or was blocked open. As noted, non- ethanol fuel helps. I also bumped the timing up 4 degrees.
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green monster
Posted 2022-10-10 11:17 PM (#624825 - in reply to #624805)
Subject: RE: 331 won't start after warmed up


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Yes no difference.
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green monster
Posted 2022-10-10 11:20 PM (#624827 - in reply to #624732)
Subject: Re: 331 won't start after warmed up


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UPDATE and SOLVED.
I added a 12v bypass to the ballast resistor so the coil has 12V while cranking and it starts better hot or cold.
It has never started so well as it does now.



Where would you set the base timing at for this engine?
Does everybody set the base timing with the vacuum advance line disconnected?

Thanks for all your help

Edited by green monster 2022-10-10 11:24 PM
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Powerflite
Posted 2022-10-10 11:42 PM (#624828 - in reply to #624732)
Subject: Re: 331 won't start after warmed up



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I set the timing to just before maximum vacuum. Then I back it off if there is any issue with pre-ignition under load. Setting it to spec isn't very useful because I usually go back and advance it more from there anyway.
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Powerflite
Posted 2022-10-10 11:46 PM (#624829 - in reply to #624732)
Subject: Re: 331 won't start after warmed up



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It sounds like your ignition circuit has a lot of resistance in it that gets worse with temperature. You might want to monitor the voltage when cold and when hot. If it dips too low, it won't give you an efficient burn while driving.
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Shep
Posted 2022-10-11 10:16 AM (#624837 - in reply to #624732)
Subject: Re: 331 won't start after warmed up



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I had mine at 8 degrees btdc. Common to find the vacuum advance canister does not work, and tough to find a good one.
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57chizler
Posted 2022-10-11 2:10 PM (#624842 - in reply to #624827)
Subject: Re: 331 won't start after warmed up



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green monster - 2022-10-10 8:20 PM

UPDATE and SOLVED.
I added a 12v bypass to the ballast resistor so the coil has 12V while cranking and it starts better hot or cold.
It has never started so well as it does now.


That tells me the starter is drawing too much current and dropping the ignition voltage.
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green monster
Posted 2022-10-11 5:39 PM (#624848 - in reply to #624828)
Subject: Re: 331 won't start after warmed up


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Please explain just before maximum vacuum.
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green monster
Posted 2023-08-12 4:18 AM (#631295 - in reply to #624732)
Subject: Re: 331 won't start after warmed up


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Update: I found that the vacuum advance diaphragm was also junk.
It runs very nice now.... warm or cold.
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Shep
Posted 2023-08-12 1:21 PM (#631298 - in reply to #631295)
Subject: Re: 331 won't start after warmed up



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Where did you find one, and use the same shims as the old one.
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