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  #46  
Old 05-18-2013, 09:49 AM
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Originally Posted by rockittsled View Post
I knew about the 7 volts, but did not realize it is 3-phase. guess that wouldn't work on a electric choke conversion, use the 12v instead
The alternator itself is a three-phase system; it's not clear to me why you say this is insufficient for powering the choke. The heating element in any choke is just a dumb heating coil; all it cares about is the RMS level. The factory chose the stator terminal to power the factory electric-assist choke because it's the only power source that's hot when the engine is actually running (vs. just having the key on), not because of any specific characteristics of the waveform itself.

Most people use 12 volts for an aftermarket electric choke simply because that's what the manufacturer calls for. If you're installing an electric-assist choke (like my picture), this still needs a primary heat source. The factory electric assist will not kick in until the hot-air stove brings the heating element to a certain temperature.
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  #47  
Old 05-18-2013, 11:34 AM
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Originally Posted by rockittsled View Post
I knew about the 7 volts, but did not realize it is 3-phase. guess that wouldn't work on a electric choke conversion, use the 12v instead
I'm not sure why they call it a three phase supply unless it is just a trade nickname among mechanics. Three phase power, simplified, consists of two legs pulling alternatively to a common neutral.
Single wire tells me single phase.
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  #48  
Old 05-18-2013, 11:55 AM
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Originally Posted by rogue40 View Post
I'm not sure why they call it a three phase supply unless it is just a trade nickname among mechanics. Three phase power, simplified, consists of two legs pulling alternatively to a common neutral.
Single wire tells me single phase.
An alternator is a three-phase system; it's not any sort of trade name. The three windings of the stator are constructed in a "wye" configuration; the three legs are then fed to the rectifier bridge, the "north" side of which serves as the alternator output. Three-phase power is the name given to power generated from three "taps"; the phase between successive legs are 120 degrees apart. "Three-phase" has to do with the mechanism in which the power is generated, not how many wires are made available in the end system.

Here's a picture to describe the mechanism. The three-phase waveform is shown in the top right. The configuration used in these trucks is shown in the lower left. You don't see this waveform in practice because the waveform is rectified and the battery provides filtering.

Click the image to open in full size.

When I started this thread over 4 years ago, the intent was not to describe charging system mechanics or power generation theory. If that topic is of interest then I welcome you guys to start a new thread.
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  #49  
Old 10-23-2013, 01:12 AM
Hellbore Hellbore is offline
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I have a question:

I share a '76 f-150 with my father, and sometimes he works on it. At some point he decided that the automatic choke wasn't working right (I don't know if it really was or not). So he gutted the automatic choke, unhooked the hot air lines, and installed an aftermarket manual choke.

Thing is, after he put this back together, he left off both the gasket between the automatic choke and the carbeurator, and the gasket for the automatic choke cap. I'm not sure what else he did to it, but the cap fits loosely and moves around.

So what I noticed is that there's definitely a vacuum leak around the choke's cap, and even if there wasn't, the flare fitting that should pull in hot air isn't hooked up to anything, so it's a vacuum leak no matter what.

Would this kind of vacuum leak be enough to cause hard starting and make the truck run crappy when it's cold? In cold weather it's VERY hard to start, even with the manual choke closing the choke all the way. The engine just can't get enough gasoline and it even has lean backfires.

The reason I'm a little confused is, even the way it was originally hooked up from the factory, it seems like it's already like a "vacuum leak" because the negative pressure in the choke pulls air in through the hot air lines, and that air comes from inside the air filter, but outside of the carb itself. So how is this not already enough of a vacuum leak? Is it because the choke or the air lines or something restrict how much air can be pulled in, to a level that doesn't mess up the engine vacuum too much?

Anyway, the way it was, with vacuum coming in around the cap, it was making a loud sucking noise when the engine was running. I put a gasket between the choke housing and the carb, and then plugged up the hole inside the choke housing where the vacuum comes through, so it's all sealed off now, no more outside air can be pulled in through the choke at all. The engine seems to run better.

Before it was hesitating off the line and when going around corners, and would sometimes stuble and lean backfire, and it was very hard to start when cold. I drove it around after sealing this off and it seemed improved.

I don't know yet if the hard starting is solved, I'll have to see in the morning when it's cold. Fingers crossed...

One more question - Now that this vacuum route is plugged up, would it make sense to redo the timing and re-adjust the carburetor? I remember last time I adjusted those 2 things, I was having some problems because the vacuum readings were inconsistent or something, or I couldn't get the result that the manual said I should get or something. It seemed like I had to richen up the mixture more than it should be in order to get the engine to start, then once the engine was warm it would run rich.
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  #50  
Old 07-22-2014, 03:24 PM
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The hot air tube is gone and the fresh air tube was capped off by PO.....will the engine still run?
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  #51  
Old 07-22-2014, 03:41 PM
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Folks,

In the future, please start a new thread if you have any specific questions. This is a 6-year old tech writeup; my intent was not to field individual questions in this thread.

To answer this latest question: yes, the engine will run. The engine will struggle to run as it tries to reach operating temperature in the absence of a properly functioning choke.

Please start a new thread if you have any further questions.
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  #52  
Old 07-23-2014, 01:55 PM
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make it a sticky!
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  #53  
Old 07-30-2014, 10:09 AM
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I need to replace my hot air tube where can I find a metal line like that ?
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  #54  
Old 07-30-2014, 10:22 AM
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Please see my last post in this thread.

I already answered that question in your other thread in my very first post.
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  #55  
Old 07-30-2014, 10:59 AM
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I checked your first post in my other thread and you did say I needed a stove repair kit but did not say where I could get one. Any help would be appreciated.
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  #56  
Old 07-30-2014, 11:11 AM
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Originally Posted by jomoflymo View Post
I checked your first post in my other thread and you did say I needed a stove repair kit but did not say where I could get one. Any help would be appreciated.
A choke stove repair kit Dorman PN 55111... available from your local auto parts retailer. If wanting a repro then NPD, Mac's, LMC, etc.

Dorman® Help!™ 55111 - Choke Stove Kit | O'Reilly Auto Parts
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Old 07-30-2014, 11:11 AM
 
 
 
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