1984 Chevy C-10 Carb Help Needed

[gconn77]

This is a new thread moving on from:1984 Chevy C-10 Vacuum Hoses and PCV Questions.

Basically, I am moving onto the carb now. I am having trouble with it and have a few questions regarding it. First off, I want to post two pictures below. I have labeled each part with a Reference number. (Ref #A thru Ref #Q). If someone could, please name and identify all of these parts according to the reference number I have assigned them. You can click each of the two photos for a very large view:







When you post your responses, can you also tell me not only the names of these parts, but also what their function is.

The motor is very hard to start in the morning when it is cold. I have spent some time trying to get things proper with this truck and motor. Previous post (link is provided at top of this thread) I had problems with the vacuum lines and emissions. As it turned out, all the emission components were removed by previous owner(s). At any rate, I have the basic vacuum system hooked up fine now. I have the proper connections from the carb to the canister, PCV, etc. I have removed all the BOLT CAPed hoses with the prober rubber caps purchased at Advanced Auto. All is good in that department.

However, still have trouble with starting the motor in cold morning. Learning that my carb has also been rigged in someways. The photo below shows a tie wrap tied around something in the electric choke area. Click the image for a bigger size photo if needed:




I wanted to remove the tie wrap simply because I know the previous owner(s) installed this to try to rig out a solution to a problem that I obviously do not know about... I knew that if I cut the tie wrap off, then it would probably result in a problem that would need to be corrected. Needless to say, I DID remove the tie wrap and here is my problem.

Please view this photo below, click on it for bigger size if needed:




The tie wrap was holding REF #A down. After removing the tie wrap REF# A lifted up, which closes REF #C. Engine will not start with REF #A lifted up. Now I can push down on REF #A and it locks in place and stays down. However pushing on REF #B releases REF #A and REF #A lifts back up.

In addition to this finding I have also discovered another vacuum hose that is not connected. Please view the photo below, click on it for a larger image if needed:




In this photo you will see the vacuum line that was lying loose... just to mess around I pluged it into the port seen in the photo which is on the back of the carb. Please tell me where this hose is SUPPOSED to be connected. Remember, this hose was found lying loose... I just stuck it in the back of the carb to see what would happen... and nothing does.

Also, I can tell that REF #E is some kind of vacuum operated system.

I really appreciate your help in advanced. Also when referring to the reference numbers... please specify which A, B, and C you are talking about... A, B, and C are the only duplicated reference numbers illustrated.... so if you tell me what Ref #A is... besure to tell me which Ref #A you are talking about..

Thanks Again,
Garry

[TrainD5115]

I'll get this rolling for you. First off that is definately not the stock manifold. Reference letter E is an old choke coil from a much earlier model vehicle and I'm thinking the reason for the plastic tie was to hold the choke in the full open position. Judging by the condition of the choke cover and the missing electrical connection, I'd say your choke is not working. As for the first photo here goes:
A: Vacuum break assy-secondary side (rear) this operates your choke and kicks the secondaries in when it gets the proper vacuum signal
B: part of the vacuum break (also called choke pulloff) assy, I guess you would call it a plunger. I recently replaced this on my carb and the entire piece is sold as a whole so it doesn't really break down any more than that.
C: Link-secondary side (rear) vacuum break to choke; this rod (link) moves the choke open or closed depending on the signal it receives from the vacuum break and the choke
D: secondary throttle lockout pin; this contacts with the secondary lockout lever to prevent the secondaries from operating until the engine has warmed up and the choke is off (open)
E: old choke coil from another (much older) vehicle
F: Fast idle cam (looks like it) hard to tell from the angle. This cam opens throttle more when engine is warming up (choke on)
G: Vacuum break assy- primary side (front) Not sure what this does exactly as my carb is older and does not have one of these
H: This is part of the front vacuum break
I: Choke lever - this connects the choke blade to the choke operating rod
J: This is an adjustment screw of some type for the vacuum break
K: Secondary air valve lever - this connects the secondary buterflies to the vacuum break rod
L: Unable to identify that part.

[TrainD5115]

Here goes on the second photo and guys feel free to correct me if I am getting any of this wrong.
M: These are the secondary butterflies-they open when the proper vacuum signal is received
N: Choke blade - this closes and creates a vacuum to start the engine when it is cold. The vacuum break should push this open slightly after the motor fires up, Judging by all the soot, I'd say your carb is running very rich
O: Pump lever - actuates the pump shot into the carb. If engine is cold it requires a bigger pump shot than if it is warm.
P: Not sure what this is
Q: Auto trans kick down cable - operates the transmission
R: Vacuum line that should be connected to your brake booster
S: This should be where the trans vacuum line should be connected
T: Vacuum port that connects to the rear vacuum break - this should be a timed vacuum port, meaning that it only supplies vacuum under a load.

[TrainD5115]

As far as your choke goes I can only tell you how it is supposed to work. The choke blade should close and create a vacuum for the cold engine, making it much easier to start. Once its started, the vacuum break (choke pulloff) should push open enough to allow the engine some air. If it doesn't open up enough the engine will run rough. As the engine warms the choke blade should continue to open until it is completely forward (straight up or just slightly forward). I know there are plenty of guys that have functioning electric chokes that can give you much more help. I have a non electric hot air choke and a slightly different set up on my 79.

[Mike76251]

On chokes.........
12 volts go to that plug in the side of the choke.
That 12 volts comes off of the oil pressure sending unit usually at the back top of the block.
The 12 volts operate a heater that keeps the choke from running all the time.

[gconn77]

Originally Posted by TrainD5115

As for the first photo here goes:
A: Vacuum break assy-secondary side (rear) this operates your choke and kicks the secondaries in when it gets the proper vacuum signal.
T: Vacuum port that connects to the rear vacuum break - this should be a timed vacuum port, meaning that it only supplies vacuum under a load.

Question: Ref #A on the first photo is the Vacuum Break Assy-Secondary Side (Rear). You said that this operates the choke and kicks the secondaries in when it gets the proper vacuum signal. How do I give it the proper vacuum signal?

Ref #T on the second photo is the Vacuum port, meaning that it only supplies vacuum under a load. Now I posted earlier that there was not a hose connected to this. Just messing around I connected the hose from the back of Ref #A found on the first photo to it. Remember I don't know if this is correct or not. So my question is this: Where do I connect Ref #T to? and how do I create a timed vacuum port so that it only supplies vacuum under a load?

Originally Posted by TrainD5115

R: Vacuum line that should be connected to your brake booster
S: This should be where the trans vacuum line should be connected

Ref #R seems to be connected fine. Ref #S There is a total of three places where hoses can be connected to it. Two posts on the side and then one larger post (which has the rubber cap on it) on the very top. My question is this: What needs to be connected to the larger post (which has the rubber cap on it)? If it is emissions related, then forget it I will keep it capped. However, if it is an essential part of creating the proper vacuum and is creating or contributing to my vacuum problem with the carb, then please let me know.

Originally Posted by TrainD5115

I'm thinking the reason for the plastic tie was to hold the choke in the full open position. Judging by the condition of the choke cover and the missing electrical connection, I'd say your choke is not working.

What is the name of the system that is being substituted and or bypassed by the previous owner(s) securing the plastic tie wrap around the choke to keep it in the full open position?

Or, in other words... what is broken or malfunctioning to cause the previous owner(s) to create the "Quick Fix" and "Rigged" solution of securing a plastic tie wrap around the choke to hold in permantly in the full open position?

I guess to sum things up... I am thinking that I have two problems. (1) is the issue with the tie wrap.... (now removed) and the electric choke not releasing on its own. (2) The proper vacuum connections.

Regards,
Garry

[TrainD5115]

The carb is supposed to send the vacuum signal to open the secondaries at a predetermined point. If you apply enough throttle while the engine is running, you should see the secondaries open. You can do this by hand with the hood open and air cleaner removed. As far as the vacuum port on the top rear of the carb (ref T) on my carb it is connected to a tube that runs down to the manifold. Your rear vacuum break should be connected to the lower port that is under this one and slightly under the rear of the carb. The part with the rubber cap is not really emissions related but like I said before, on my truck, this is where the vacuum line going to the trans is connected. The piece that I personally think was being by-passed was the plastic cover that should be held in place by three screws. This is your electric choke. If it was broken or stopped working right it could cause the carb to run poorly and waste gas. If it doesn't close the choke blade it will definately contribute to hard starting because when the choke blade closes it creates the vacuum to help turn over the motor and pull the fuel from the metering systems in your carb. The manifold is cold and very little fuel reaches the cylinders as vapor during cold starts. If you hook up the electrical connection and it doesn't close the choke when you try to start a cold engine then you will have to try a new one. They are easily to get from auto parts stores. Again, I have a slightly different system than yours but the basic operation is the same. I am also assuming that all of the other parts of your choke system are there and in the right places. This carb could have been pulled apart and who knows what done to it.

[elvis50138]

I think most of your questions could be answered at the following link:
http://carburetion.com/diags/4mv.jpg

In general there is a lot of good info at the carburetion.com site.