Presently there is a thread that sounds almost identical to this except my 4.9 has problems starting cold. Here is my history in a paragraph. For approximately the last 4 months I have been having problems starting my truck when cold. Once I get it started and it gets warm it runs like a champ. I can drive around all day long, turn off turn on etc... I have turned the truck off for up to 1 hour and it starts right up. If I drive one day and park for the evening and try to start the next day I have the same problem. I have replaced the plugs and wires. The truck is a 1982 with a 1976 4.9 carberated not EFI. I don't drive often, I use for hauling firewood and other stuff. Also have replaced the manual fuel pump and portions of the fuel line within the engine compartment (rubber only).

 

Calwell,
Sound like the choke is not working. With the engine off and cold take the air cleaner off so you can see the choke plate. Push the throttle linkage as if to accelerate. Two things should happen,

(1) The choke plate should go almost closed maybe 1/8 inch open.
(2) The accelerator pump in the carb should squirt raw fuel into the carb bore. You may not see the fuel squirt because of the closed choke plate. If so then hold open the choke plate look inside and move the throttle again. Do not do this too many times, you could flood the engine.

If the choke plate does not snap almost shut then find the usuially black colored round spring housing (1.5 to 2 inch diameter). Take note of the current position of the spring housing by marking a line somewhere from the black spring housing to a part of the carb casting (just in case you want to get back to the original setting). Loosen the three screws, hold the throttle slightly open and turn the black housing. If the choke plate does not start to move turn it the other way. Turn it until the choke plate is 1/8 inch or so open. While holding the spring housing in place snug up the three screws. You might have to do this a couple of times to get it right. If If the choke plate does not move while rotating the spring housing cover the spring inside may be broken.

If there is not a squirt of fuel you would probably notice it during regular driving. I can address that later if need be.

 

The one thing I have noticed is the choke plate is wide open. I will follow your instructions and get back to you, probably later this evening or Tuesday

 

Wide open when cold?

 

With the engine off and cold I took the air cleaner off so I could see the choke plate. I pushed the throttle linkage as if to accelerate. The two things that should have happened didn't.
The choke plate did not move it stays wide open.

I then found the round spring housing (the spring is located between the back of the carb the cab)?

I assume the choke plate is not supposed to be wide open all the time? That is all I got done this evening.

 

Caldwell F150,

Use the "search" feature at the top of the page and type in "Choke adjustment 101" and see if that helps.

 

If it's cold out, the choke does the most important function to get your engine warm and stay running.

As the air gets colder, it gets denser, so theirs a lot more of it going into the engine when the air is cold. When you increase the amount of air going into a motor without the proper increase in the amount of fuel, this means the motor is running lean.

To keep the motor running when it gets cold, the choke sits above the throttle valve and reduces the amount of air coming into the motor, while the amount of gas stays the same. In short, it temporarily rich-ens up your fuel mixture.

While the vehicle is running after the choke is set, the choke is normally connected to the fast idle cam on the side of the carburetor. As the choke warms up (be it electric, climatic, or water heated), it slowly opens to adjust for the motor getting warm. As it opens, the fast idle cam knocks the motor down from high idle in steps down to curb idle. Say when you first crank it, it should be around 12 to 1300 rpm maybe. As the choke warms up, it would knock it down to maybe 1000 or 900, then down to 5 or 600 rpm.

Since you say it doesn't set the choke when you mash the throttle (I'm assuming your doing it all the way wide open then letting it go), then it sounds like the choke is not hooked to the linkages on the carb. Take a look on the back of the carb under the black ufo looking thing next to where your throttle cable hooks up and tell us what you see.

It's not really a big deal if the choke isn't hooked up, it's just a convenience. When you first crank it in the mornings when it's bone cold, pump the gas pedal 2 or 3 times, crank it, and when it fires off, hold the throttle at about 1200 rpm with your foot to help the thing warm up.

 

Caldwell,
When the engine is cold and you do as I suggested, the choke plate should snap almost closed. If it does not then adjust the choke spring housing as I suggested. If you cannot get the choke plate to move then there is a spring problem (or there is a missing or mis adjusted linkage). The spring is a special spring, it is a bi-metalic spring. This means that there are two different metals bonded together. When this bi-metalic spring sees a temperature change it will either stretch or contract (depending on which way the temperature change is). As it changes length (due to the temperature change) it will either open or close the choke plate. When the engine is cold the choke plate should be closed after you tap the throttle. As the engine warms up the choke plate will open for normal driving.

As far as the raw fuel squirting into the carb bore I probably should not have mentioned it. If when you drive the vehicle and it does not stumble (when trying to accelerate) the accelerator pump is probably working fine.

As I said before, when the engine is cold the choke plate should be closed after you tap the throttle. If this does not happen then the spring is broken or there is linkage missing. Take some photos of the linkage and general carb area and post. A picture is worth a thousand words.

Just remember, this is not a really big issue. Just the limitations of communicating on the internet is the problem. If you had your truck in my driveway for 30 minutes, the fix would be identified. If parts are needed it may take a few days to implement the fix.

 

Sorry for the long gap between answering. It looks like a choke problem. I will search for "Choke Adjustment 101" as 1986F150six said and get back and let all know what outcome is. Thanks all