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automatic choke woes

You could, some people like it, I think the electric chokes are great (as great as any carbed application can be lol) and I'd rather be able to start it and not have to sit there to play with it.

The transition from closed to open should be pretty linear, I don't know the failure modes of these things, it would seem odd the choke would work right opening and closing, but not in between.
 
I agree. It seems to take a while for the engine to warm up too. I mean I know these old trucks are cold natured and all, but it takes like 15 or 20 minutes to get up to temp. I wonder if the thermostat is stuck open. Would that cause a problem? It's only supposed to be about 40* tomorrow morning, so if it does better then I'll know it was just the subfreezing weather the past couple of days.
 
I converted every auto choke I ever owned to manual. But I grew up driving a factory manual, so I knew how to work it.

One of the main things I liked about the manual part, was that I could put the engine on fast idle anytime I needed to, without the choke being closed.
Great for jumping off a car with a cheap set of jumpers, or using a PTO winch when winding it up by yourself.

Not sure which of the many types you have, but most of them are electric assist, not pure electric.
The bimetallic spring inside the cap responds to heat. The electricity heats it up, but so does the warm air from the engine drawn by the vacuum. Usually there is a depression in the intake manifold with a steel tube going to it that a vacuum line draws air over the manifold and across the spring.

Remember also, in most cases, the choke plate will not close all the way when cold until you depress the throttle.
This lets the plate close, and puts the carb on fast idle. All that slop in the linkage lets things move independently.
For instance, the fast idle will stay on even though the choke plate has opened from warmth until you open the throttle.

With a manual conversion, on a warm engine, you would open the throttle slightly, pull the choke all the way out.
This would close the choke plate and put the throttle on fast idle.
Then let the accelerator off, and push the choke all the way in.

This would open the choke plate all the way, but leave the engine on fast idle until you blipped the accelerator.

I would usually pull the choke out on a cold engine to the point it seemed to like from trial and error over some time.
Then, crank the engine, and if it was OK with it, push in the choke a little letting the fast idle keep it running.
As soon as I got going, if there were no immediate stops, I would push the choke all the way in to reduce gas usage and possible washdown.

So, in most cases, the choke stayed on less with a manual than auto.
 
It kinda does seem almost like it's staying on too long. I used to ride motorcycles with manual chokes (of course) way back before they were all fuel injected, and they would run kinda like that when you forgot to turn the choke off. I don't think they would try to stall like this is doing though. They would just act like they were low on power.
 
if it's staying on too long, you'll see it in a plug reading usually, burning too rich, sooty...

it would make sense if you adjusted it too much to close it up when cold..
 
I'd throw a 195 thermostat in it too,an engine should be up to full operating temparature within 10 minutes,especially if you drive it away soon after starting it up--unless your in alaska and its 30 below or something...

I liked manual chokes too,you can save quite a bit of fuel if one is used properly..I have trouble remembering to push the knob in all the way though ,on the few trucks I had one on sometimes..:doah:..
I tried rigging up a idiot light to remind me the choke was still partly closed,but it didn't pan out too well..

A lot of Q-jets end up having a dead choke pull off after many miles and that will let it run way too rich and even flood and foul spark plugs so badly it wont even re-start --that little bit it opens the choke butterfly as soon as it starts is critical...

On some carbs the choke stays closed too long even if the electric spring dewhickey is working and adjusted right ,because the heat riser passages under the carb casted into the intake manifold that lets hot exhaust gasses heat the base of the carb up get clogged with soot or someone took the heat riser/EFE valve out of the exhaust pipe,or used intake gaskets that block off the heat riser passages--or put a spacer under the carb or an adapter..

In colder climates carbs can be very fussy when the hot air stove going to the stock air cleaner and the air filter housing itself gets "deleted" for a hot rod version or the original one has faulty vacuum doors..many aftermarket intakes dont have these heat riser passages too,that can be a problem in cold climates until the engine gets fully warmed up--which might take 20 minutes if its frigid out..

I have had more than one "cold blooded chevy" that ran like dogcrap with the original air cleaner ditched --carbs would ice up and stall at idle,on damp cool days it was darn near impossible to drive one truck I had,frost built up in the carb so badly the gas pedal would stick wherever it was held at vruising speed,then stall when you got it back to idle..

I had to get an original air cleaner ,hooked up the hot air stove pipe and I even applied a constant vacuum source to the EFE valve to hold it closed and sent more heat under the carb,I would leave it that way all winter,and it made the truck 100% better as fas as driveability..the engine was a 305 with an Edelbrock carb ,had a Holley intake..it ran sweet in the summer with the cool looking hot rod air cleaner and all the original "crap" missing,but come november,I wanted to park it for the winter till I decided to put the stock air cleaner setup back on it and hook up the EFE valve..foggy days at 40-50 degrees were the worst!..
 
A little update here.

I visited my dad for Thanksgiving and convinced him to look at my carb. He verified that I did have the choke a little tight, so he loosened it a little and showed me what kind of tension it needs to have. However, once it was properly adjusted and working like it's supposed to, the engine still wanted to stall at idle and would still smoke out of the tailpipes (only a vapor-type smoke) even when the engine was fully warmed up. He asked me if I had adjusted the air/fuel mixture and I told him I had, but several years ago. He then proceeded to adjust the screw on the passenger side (can't remember if that's air or fuel) and it made a difference, but when he messed with the screw on the driver's side, it made no difference at all - even when he turned it all the way in or out. So I still have a problem. The engine is still running bad at idle. I'm thinking something is wrong in the carb, but I don't know what.

Any more suggestions?
 
those are not air and fuel.. they are both "the" air/fuel idle circuit mixture... same thing, just one is for the left bank, the other the right... rule of thumb is both should be out 2 turns.. both even... but a vac gauge can be used to dial it in for max vac.. if one is not reacting, either that circuit is blocked, or the screw was over tightened at some point and the needle is damaged...
 
Roger that.

So I'm thinking that the passage must be blocked. How can I unblock it? Without taking the carb apart I mean?
 
slowly turn it in till it stops, notate how many turns.. should be around 2.. than turn the screw all the way out till the screw comes out.... use carb cleaner liberally in that hole with the little red straw..

inspect the needle, it should have a smooth, even taper down at the end... if crushed, you'll see a ridge... reinstall until it lightly seats stop, back out 2 turns... verify other side operation and adjustment...
 
Excellent. I didn't know if it would come out easily like that or not.

On a side note, I drove it down to a swamp and sandy beach on a river down near my parents' house and it ran good after it had been running a while and I got on the throttle a good bit. So maybe it just needs cleaning like you said. I'll try that. Thanks.

56B5B1BD-C488-455D-BF6D-4E437860E873.jpg
 
and keep in mind, it's only an idle circuit... once off idle it really isn't doing anything... that's THE most common misconception, that those screws are an air/fuel adjustment for the whole operating range..
 
Good to know. That must be why it will run fine at any time except when it's idling. I'm sure my good ol' dad has told me all this stuff before; I just have a bad memory. I wonder how long it will be before there's no one around that remembers how to work on a carb.
 
Probably not too long!...a lot of the guys I knew who worked on the 73-87's during the height of popularity are now dead,or have moved away...

When I listen to "Car Talk" on NPR,I often hear them tell owners of pre-80 vehicles who need a carb fixed or other "aincient technology",to look for the OLDEST mechanic with the grayest hair,and fewest teeth!..and dont trust anyone younger than the vehicle is to know how to fix it properly!..they also say to try retirement homes ,if your lucky you might find an old mechanic thats not senile and remembers how to work on "antiques"..

They say that in jest,but when my boss needed a Packard "Ultramatic" automatic tranny rebuilt,he was directed to a guy in a nursing home who was "the best" back in the day at fixing them!--he was able to bring him two trannies out of junkyard cars he had,and he made one out of the two,and rebuilt them,while sitting in his wheelchair,he had to have some help of course,but without his guidance,that Packard would never have moved again--no tranny "experts" in our area wanted to tackle rebuilding it..
 
I guess it's kinda like classic rock music. I was talking to a co-worker a while back (who was like 24 at the time) and I asked him if he liked Eric Clapton. He goes "I think I've heard of him before." :doah:

That's why I go to see the old Southern Rock musicians whenever I can and learn all I can from them. Once they're gone, I don't know if anyone will remember how to rock like they did. I've tried to get some kids turned on to real music from the 60s and 70s, but they just can't appreciate it.

Same thing with these old trucks with carb and leaf springs. I don't know who after us will have any knowledge/interest in these great old machines. That's why I'm trying to at least learn a little something. Remembering what I learned is a different story... :haha:
 
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I grew up with old vehicles,and classic rock, so I feel uncomfortable with most anything newer..todays music I cant get into at all,as far as rock goes--after being spoiled by Led Zeppelin,Sabbath,Areosmith ,Creedence and all the other greats,todays "performers" pale in comparison in my opinion..

I often wish I were born ten years earlier even,when things were really simple and could be easily repaired,and seldom HAD to be!..

I feel a lot more secure driving and owning something I lnow how to fix,CAN fix,and doesn't baffle me with mysterious symptoms no one can diagnose thanks to a computer or multiple sensors..and doesn't have an engine compartment cramped so tight a midget couldn't even get his hands on half the parts too..I dont like the fact vehicles have evolved into complicated electronic controlled tupperware human transporters,I liked things better when they were simple..yet still modern enough and efficient to be daily driven comfortably..
 
You usually have to get the idle way down there before it's really running on the idle circuit. A lot of trucks get the idle turned up because there is some problem and it's really running on the off-idle or even a bit on the main circuit. So turning the idle mixture screws does nothing when you idle at 800rpm and you shouldn't be surprised. Even if your idle speed won't be that low when you're done, get it way down like 400-500rpm for setting the idle screws. You'll end up with a better idle and less tendency to stall when that is right, even if your long-term idle speed will higher.

You should check out the timing to get it to idle that low. There is a bunch of stuff in the vacuum circuit to the vacuum advance can, like thermal vacuum switches, hoses, check valves and flux capacitors. Something could be broken or disconnected. Then check out the mechanical advance and get it moving freely. It almost always becomes stuck eventually and with the timing off you can't get the idle right and the carb dialed in. Use a timing light to know where you're at. You either need a dial light or timing tape on the balancer.

Finally, if all of that is right and you can't get the idle screws to have any affect, the passages in the idle circuit may be blocked and the carb probably needs cleaning.
 
That's what's leading me to believe it's just clogged up. Now I did have it idling at 800 rpm or so. Now I've slowed it down to about 500-600, and I was thinking about idling it back up to try to smooth it back out and maybe keep it from trying to stall, but I want to fix it right.

I checked the timing with a borrwed timing light a few years back and turned the distributor to the right spot. The vacuum advance was working at that time, but it has been a while, so I guess I should check that stuff out too.

It's not really stumbling or trying bog when I first hit the gas. The idle just gets slower and slower the longer you let it idle until it eventually dies. I'm going to run me some Lucas Oil fuel system treatment through it and see if that helps. I've used that stuff in several vehicles that were idling rough and it helped them a lot.

You know, I just thought of this, but I did run the tank down to less than half a gallon a couple of weeks ago. I wonder if some trash got sucked up off the bottom of the tank. I just put that tank in there in 2011, so it probably isn't rusty yet, but you never know.

Thanks for all the advice guys. As you can tell, I'm not the world's greatest mechanic here. I just like to drive my old truck dangit.
 
More of a general question, can you put 90+ PSI through the idle adjustment ports with the adjusters removed? Works fine on lawnmowers.
 
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