My 390 has an idle problem when the weather is cold. I tried to adjust the electric choke so that the choke stays open longer due to the cold weather. It does not help that much. You almost have to start it up and play with the idle until it has completely warmed up which can take a little while. It is a brand new holley 4-barrel so not much has been adjusted other than maybe the idle speed and the choke cap.

 

Sounds like you're not getting enough choke.

Before start up in the morning, pump the gas pedal twice, this sets the choke.
Take the top off the air cleaner, you should have 1/4 to 3/8 gap (ballpark) between the choke plate and the air horn. When you start the motor, the high idle cam should keep the RPMs up without you doing anything.

The Thermal Air Cleaner helps driveability also.

If you don't have instructions for set up and adjustment of the choke, try the Holly web site.

If you don't have any luck there, post your engines displacement, year of manufacture, which truck, and carb's model #. I'll see what I can dig up.

Good luck, Mike

 

Is this a stock 390 or did it get rebuilt with a bigger cam?

Sounds like a typical FE, to me - even my 360 with stock 2bbl was a pain in the butt to start in the cold - and the choke was working correctly.

Like Hypoid said, make sure you set the choke correctly with a few pedal pumps before starting, and do not touch the throttle until it runs a minute or two - as soon as you touch the pedal after starting, the choke will open slightly and lower the idle.

Also, the high-idle cam has an adjustment on it, so you can raise the idle even higher when choked - get back to us and we'll help out more...

art k.

 

UPDATE:

First off can the 12V wire off the choke be connected to the alternator? If so where on the alternator?

Went out to fire it up and before i say anything else, at this point the choke plate is vertical. I guess that means its wide open. Ok I pump the gas 2 times bout a half a second a piece and start it up and it will idle for about 2 seconds and then quit. Now I have to fight it and play with the gas until it eventually idles like a big boy hahaha (about 5 min). Thats really the only option when its cold out. It will do the same thing in the summer but not as bad as colder weather. The mixture screws are about 1 1/2 out on each side, the exhaust smokes a little but when its warmed up it goes away and it doesnt smell bad. After warmup, the idle is smooth and doesnt backfire and is very responsive. So basically what im saying is am I pretty much stuck with the fact that I have to play with the idle untill its warmed up or are there still some tweaks I can do so I can pump it, start it and have it idle without a fight?

 

Okay, I think you may have the opposite idea about how a choke works. When it's cold out, you want the choke closed, with the plates almost completely closing off the air flow. As the engine warms up, that plate should open slowly until it is at vertical for normal operation.

The way I understand it is this: you engine will only run well at a certain ratio of air molecules to gasoline molecules. But when you heat up air, the molecules spread farther apart, so you get less air molecules. No problem, they can calibrate your carbuerator to work with air that is heated up. And they do that because your engine will be hot 99% of the time.

But that other 1% is on start up on cold mornings. The air is way too dense to get the right mixture. There are only two ways to deal with that until the motor warms the air up: add more gas (which you've mastered by bumping the gas pedal and triggering the accelerator pump to squirt more gas in there ) or by taking away some of the air (which is what closing that choke plate does).

Everything you are describing is what an engine will do when the choke isn't closed at start up and the engine is running lean. I think someone has rotated the whole electric choke assembly so that it will always be open, which is a common thing to do here in the warmer climates.

Loosen the screws and turn that bad boy until it is closed on a completely cold engine. Then you might want to try 2 turns out on the mixture screws.

I think I've heard that the choke wire goes to the alternator so it sees only 6volts, but I'll let somebody else who has one of those animals tackle that question. This whole discussion is why I bought an Edelbrock with a manual choke. I just have a cable operated **** in the cab that I can pull to close the choke.

Hope this helps, and if I misunderstood you and you already knew all this stuff, I apologize.

Chris

 

thanks for the info..Looks like i got a little cofused haha. I'm gonna turn that choke cap towards the cab (per manual) tomm morn so i know its cold.

This may be a little confusing but see if you understand it. When I have my left hand to hold the flap closed, I use my right hand to open the throttle a bit to allow the flap to completely close. But when i let off the throttle the flap doesnt stay closed. Bacially the flap is always open all the time. How am I going to shut this flap?

 

When the engine is cold, key off (if it's an electric choke), if you tap the throttle and the choke plate doesn't close almost all the way, then something is wrong. Notice I said "almost all the way" - it needs to be open slightly, not completely closed.

Is the carb a rebuild? It's possible the bimetallic coil in the choke cap is not lined up with the lever.

Side note: if it's a recent (last 20 years?) Holley aftermarket carb, the electric choke doesn't connect to the alternator, it needs switched 12V from the key. Sometimes you'll see an electric-choke Holley connected to the alternator, and because the alternator stator doesn't give enough voltage to open the choke, someone will adjust the choke cap so far that it won't choke properly when cold. If you aren't the one who setup the motor, it's possible that's an issue for you too...

 

First, an electric choke uses a small electric heater to warm up the bi-metallic coil under the choke cap so that it relaxes and opens the choke. The coil acts like a spring to close the choke, when warm it relaxes and opens the choke.

The heater is connected to any +12 volt source that comes on when the ignition is on. Most people connect it to the field wire of the alternator just because that is easy. However, it should never be connected to the coil wire.

Second, you rotate the cap such that the choke plate closes (by itself - not while you push on it) when the engine is cold. As the electric heater inside the cap heats up the bi-metallic coil it will relax and open the choke.

The same coil and choke mechanism operates a fast idle cam on your linkage. There will be a separate idle adjustment screw or bolt for setting your idle speed when the choke is on. (When the choke is off this cam moves out of the way and your normal idle speed adjustment screw works.) You set this for 1200 to 1600 RPM.

This is why you have to "bump" the throttle to engage the choke when you first start the starting sequence.

Also, it may help to think of the choke and the warm idle adjustments as separate circuits that interact with each other. You should set your warm idle adjustments as you always have, and should not change them. The operation of the choke causes the choke plate to close and the fast idle cam to engage, which "takes over" from these adjustments, but only for a short time when the engine is cold and warming up.

On edit:
Sorry Kerwat, I was typing when you posted. Your discussion on connecting to the alternator sounds much better than mine - the only time I did this I connected to a switched 12 volt source because I did not understand alternators.

Clint

 

This carb is a brand new out of the box unit as of about 5 months ago. Maybe it got dis-engaged from the lever when I adjusted it today. Can I take the cap off and re-allign if needed?

So I was pretty much beatin a dead horse today tryin to close the choke due to the motor still being hot.

Was hooking the 12V wire to the windshield wipers ok?

 

How do you mean "hooking it to the windshield wipers" ? That invokes all sorts of weird images in my head If you're talking about the supply to the windshield wipers, yup, just realize that with the key in ACCessory position, you'll be warming up your choke

In my experience, an electric choke with a warm motor might kick the choke closed slightly, just because the choke cap is not energized but is still warmer than normal.

You should be able to take off the cap, no problem, just don't lose the screws or the gasket (I seem to recall a paper gasket behind the cap).

Willyb, I meant field not stator, thanks for that The rest of your post was very informative !

 

Ya I just found what wire on the wiper switch was the one that gave power to turn the wipers on and just tapped into it. So if I hooked the power up right (which im confident I did) when i turn the key to ACC and pump the gas twice, the flap should close...If I take the cap off and see that it is not alligned, are there any precautions I should take into consideration?

 

No, not like that. The electric part of the choke opens the choke as it warms up - you do not need to turn the key on to close the flap.

Please make sure there is no power on the wiper wire you tapped until you turn the key on - I am not sure how the parking circuit works on the wipers.

You may want to read the Holley directions on installing electric chokes - http://www.holley.com/TechDocs/Instr...ets/45-223.pdf
directions for adjustmet are at the end of the document.

 

On my '74, my '01, and my '96/97 tbird/cougars, turn the key off in mid-swipe and the wipers do not park - so no problem there

You're on target though...

For 7677mess, if you take off the cap, you'll be able to see how it works - should be a no-brainer.

 

My FE has no problems starting up on cold mornings. FE's dont have cold starting problems from what I know. My hi po 352 with a holley starts up one on crank, and its a manual choke.

 

are you sure it is not the ignition module this sounds like a classic case of bad module when its cold it almost does not work but when warm it works fine