Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

choke/carb problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 77Jimmy, Sep 12, 2002.

  1. 77Jimmy

    77Jimmy 1/2 ton status

    Joined:
    Sep 3, 2002
    Posts:
    661
    Likes Received:
    0
    Location:
    Atlanta, GA
    Carb experts, I need your help. Let me set the stage – recently purchased a 77 Jimmy 350 w/ a rebuilt carb from a 1974 Chevy (based on the # 7044526). I am having trouble starting it up so I thought I would check the choke. After referring to my Haynes/Chilton, I tried to close the choke completely (make the choke plate appear flat) but the best I could do was to get it on a 45 degree angle. The mechanics of all the levers would not let me close it completely. Has this ever happened to anyone? Any ideas?
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Good thing your just past emmisions with the age. I am pretty sure 77 is supose to have EGR and a 74 carb is not set up to run it.
    What style choke does that have? 74 should be a stove type with a little metal box bolted to the intake. the little metal box has a BiMetal spring in it that changes shape as it heats to decativate the choke.
    I'm pretty sure that 77 was already to the hot air stye. On the side of the carb would be a bowl with a dial on it. There is supose to be two tubes out either end.. One goes down to a deal in the intake. One goes to a fitting on the back of the carb.
    Let us know what choke arangement you have. It's imprtant to know so we can figure out your problem.
    My guess is it was a stove type . No provision for it on the intake so who ever put it on jammed the choke to keep it open. If I'm right the easiest thing to do is make it a manual choke.
     
  3. 77Jimmy

    77Jimmy 1/2 ton status

    Joined:
    Sep 3, 2002
    Posts:
    661
    Likes Received:
    0
    Location:
    Atlanta, GA
    Hey Grim.

    I’m at work so I’ll give you as much info as I can off the top of my head and get the rest of the info tonight (and hopefully a pic too).

    If I’m looking at the carb from the front of the vehicle, on the left side of the carb on top of the engine I have a small metal box w/ a choke coil in it. After reading some other posts, I thought the choke coil might be bad which was causing the choke plate not to close (could this cause dieseling as well?). It’s like the levelers, etc aren’t long enough to allow the choke plate to close. Oh yea, what is EGR?

    I think this is a separate issue, but I do have a stove pipe coming up from the exhaust manifold (I think that’s right), that hooks in to the snorkel on the air filter housing. The way I understand this is suppose to work is on startup the vacuum motor closes off the end of the snorkel directing hot air from the exhaust into the air filter housing for the carb to “warm up” on. I have a few small holes in metal bracket holding the stove pipe to the exhaust manifold, which I’m pretty sure is letting all the warm exhaust escape so the carb never gets any of that warm exhaust. Also, I looked inside the snorkel and it looks like the door that opens and shuts is kind of off center so it wouldn’t shut completely anyway. Is this the kind of setup that came on a 77 Jimmy or is this something that was added by the previous owner. Also, I’ve read the replacement procedure for the vacuum motor in the Haynes manual --- is it easier to go to a junk yard and find another air filter housing w/ the vacuum motor?
     
  4. 77Jimmy

    77Jimmy 1/2 ton status

    Joined:
    Sep 3, 2002
    Posts:
    661
    Likes Received:
    0
    Location:
    Atlanta, GA
    Here's a pic of what I have.

    http://coloradok5.com/photos/showphoto.php?photo=1326

    I looked up EGR in Chiltons and I don't have it as you can see from the pic (maybe I should but I don't). I'm lost on this one. Should I just go to Advance Auto Parts and get the manual choke kit? I've seen some people on this site say they leave the choke open all the time -- is this good or bad? Also, I can't find the tech info for this carb# 7044526 in Haynes or Chilton and can't find it out on the internet either. Is it worth just buying a refurbed carb w/ a # for a 77?

    Also the stove pipe I mentioned above was bogus, unless I'm not understanding how this thing works. I found that the stove pipe actually just sat in this hole/bracket and there wasn't a hole in the exhaust manifold to draw warm air from.

    http://coloradok5.com/photos/showphoto.php?photo=1327

    What kind of emissions system do I have w/ this rig? I'm really getting frustrated b/c I've researched this thing to death using Chiltons/Haynes and it seems like my emissions and carb systems are a little bit of everything. /forums/images/icons/confused.gif
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Well the carb matches the intake and choke. Everything on the side looks right. What might be wrong is an assembly problem. The linkage that attaches to the choke plate has a cam deal inside the carb that then connects to the the exteranal choke peices you can see. They may not have got that together correctly.
    There is also a cam deal that forces the choke open some at full throttle that could have a problem.
    Hard to tell without looking at it.

    As for what emmisions you have....Pretty well none. PVC is about it on that carb. 78 is the first year of the cat. You may or may not have had a EGR originally but hay, you don't have to get a check so who cares.
    The pipe off the exhaust is a pre heat pipe. It just pulls heat off the outside of the manifuld through the tins pop rivited to the side. It doesn't pull in exhaust. What it is for is if it's real cold it's possible for the carb to freeze. Basicly the moisture in the air would freeze and make frost on the sides of the venturies. That pipe alows some hot air off the exhaust to preheat the air so that doesn't happen. The air cleaner has a "Thermac" system. It's a vacuum controled flap the will let it pull the hot air off the manifold when it drops below a certain temp. That plugged vacum port by the choke is where the plumbing for the air cleaner goes. Mine is bad so I just left it disconnected and I didn't have a problem with it. It doesn't get cold enough here often enough to be a real problem Course my truck is not a daily driver either.
     
  6. 87sm465np208

    87sm465np208 1/2 ton status

    Joined:
    Aug 28, 2002
    Posts:
    1,114
    Likes Received:
    0
    Location:
    illinois
    go fer a manual choke, my dad put one on my moms old 78 4x4 1\2 ton (350), worked fine when the electiric choke went, had no problems, other then you gotta remember to back it down when the engine warms up.
     

Share This Page