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 Light on, Idle up

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MilpitasK5, Jun 20, 2002.

  1. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    I have an 86' K5 with a 5.7L and Quadrajet Carb. It has been running good for the last few months except for my idle kinda jumping from 700 to 1000. (I've been saving up for a new carb.) Last night out of nowhere my choke light turns on and stays on. It ran normal for a while but after letting it cool down and driving it again, the idle stayed up above 1500.
    I found a few old threads saying that I should check to make sure that the choke has 12 volts going to it when the key is on and to check that the choke plate and related linkages all move freely.
    I also tried looking in my Chilton but there was nothing in the index on the choke (sometimes that book is useless!!).
    How do I identify the choke? Any other advice on checking this prob?
    Thanks,
    /forums/images/icons/confused.gif
     
  2. Blue85

    Blue85 Troll Premium Member

    Joined:
    Jul 26, 2000
    Posts:
    9,073
    Likes Received:
    486
    Location:
    Grand Rapids area
    Re: Choke Light on Idle up

    It is easy to identify the choke. The hard part is knowing exactly what the problem is or if it even is the choke. Pull the air cleaner and look at the carb. On the left side (Passengers side), it is a round deal about 3" in diameter and about 1.5" thick. There should be a male terminal sticking out that accepts a single wire for the choke heater.
     
  3. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    Re: Choke Light on Idle up

    That's a start! Thanks Blue.
    Anyone have any troubleshooting advice??
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Re: Choke Light on Idle up

    Yeah, disconnect it and wire it open until you get your new carb. /forums/images/icons/smile.gif
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Re: Choke Light on Idle up

    Keep the carb, its probably better than anything you can buy. I'll try to explain this so you know what the choke is all about. Your engine runs off vapor and not liquid fuel. Its very hard to get the liquid fuel to turn into vapor becuase everything is so cold and it just wants to condense on the intake. The choke (little flipper on the top, front of the carb) pulls shut, restricting air, and making a super rich mixture to burn what little bit of fuel that is making its way to cylinders. The warmer the engine gets, the better the atomization of fuel and the more air it can handle. Thats why the choke slowy opens.

    The high idle is also part of the choke because the oil in the engine is rather heavy when cold and other factors make it hard for the engine to maintain a lower idle, so it bumps the idle up. The big thing on the passenger side of the carb with the wire going to it has a coiled up spring in there. The spring inside looks the spring in one of those big yard thermometers. This spring is sensitive to heat, it contracts and pulls the choke shut when cold. Heat is added to it make it uncoil and your choke open. GM had several ways of accomplishing this, yours uses an electric heater. If you hold open the throttle, you should be able to pick up and down on this little green flipper on the passenger side, see the choke door close? This little flipper also brings up this shinny silver lever, that is your high idle cam. The more the choke is pulled shut, the higher it go, and the faster the idle.

    Your problem could be that the coil is no longer being heated and you need a replacement. I believe Edelbrock part number 1996 (call summit and ask about EDL-1996) would work. Edelbrock is making Quadrajets now and I just use their parts for whatever little piece I need. Any chain part store should be able to get you what you need. A part number is handy if the clerk is a real gomer and doesn't even know what car-bur-etor is, /forums/images/icons/laugh.gif . It doesn't have to be that Edelbrock one. Just undo those three screws holding the black piece and bring it into the store with you.

    Before we go yanking parts out though, lets make sure things are working properly. Unplug the little green wire as desribed before and check for 12v. You have to do this with the engine running. There is a switch that only gives the juice to the choke when the engine is running. That way you're not opening the choke if you just have the key on listening to the radio. If you are not getting any juice, time to get dirty. Go down by the oil filter and have a look just above. There should be a little sender with three wires going to it, that tells the choke when to open. Make sure the wires are in good shape. Replace that piece and see if things work.

    Sorry for the lecture, but its nice to know what everything does and why. /forums/images/icons/smirk.gif
     
  6. Blue85

    Blue85 Troll Premium Member

    Joined:
    Jul 26, 2000
    Posts:
    9,073
    Likes Received:
    486
    Location:
    Grand Rapids area
    Re: Choke Light on Idle up

    Ummm...The choke opening is mechanical. The wire is just for an electric heater to warm the bimetallic coil.
     
  7. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    Re: Choke Light on Idle up

    Thanks Blazer Boy! No worries on the lecture. I'm thankful that you took time to give that lesson! I'm at work right now and I just want to go home and work on my rig now!!!! argh...... /forums/images/icons/smile.gif
     
  8. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Re: Choke Light on Idle up *DELETED*

    Post deleted by Blazer_Boy
     
  9. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    Re: Choke Light on Idle up

    Oh yeah. As for the carb. What should I do with it. Just get it rebuilt?
     
  10. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Re: Choke Light on Idle up

    Well is there really anything wrong with it? A rebuild is defintely within your means. All a rebuild kit is basically a gasket kit with a new needle and seat. I think the major benifit of a rebuild is cleaning all the crud out of it. You'll need some star shaped screwdrivers, a flat head screwdriver (normal sized and a real wide one), small punch or nail, a hammer, some compressed air, and a little nerve, /forums/images/icons/wink.gif .

    It'll look similar to this... Quadrajet
    You'll be putting in parts 86, 2, 42, 76, 63, 24, 39, and a cup and spring on 54. The kits have excellent directions and we can help if you have a question or two.

    You may have an E4ME Q-Jet which is electronically controlled. Do you have some wires and a plug on the top, front, passenger's side, or just a dome? I'm not as big of know-it-all as I pretend to be and don't if they are more trouble or not. Dyeager535 can help you.
     
  11. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    Re: Choke Light on Idle up

    Well I had a mechanic friend of mine look at my carb and make some adjustments but there's and air leak somewhere and we can't find it. We can hear it. We changed the main gasket thing but it was still there.

    Okay, I think I found the green wire that you guys told me about and I had to splice a section (replace part of it) of it b/c I found the wire sitting on the exhaust manifold. The guys that installed the rebuilt didn't do the best job with the wires /forums/images/icons/frown.gif . A few months after the install one of my spark plug wires melted too.

    Anyway, I rigged up that wire the best I could and checked for 12volts and I think it was okay but I'm not sure if I was using that voltimeter correctly. So I went to the round thing on the passenger side to see if I could replace that coil thing but those three screws were rivets. Was I possibly looking at the wrong part? It's on the passenger side of the carb where the green wire is connected/plugged. If I was looking at the right part, how do I replace it?
    Thanks again for all your help. Sorry if I'm being a "gumba" but I'm still trying to learn. /forums/images/icons/crazy.gif
     
  12. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Choke Light on Idle up

    Well if that wire was disconnected then that's your problem. Give it a try before you replace the choke element. As for testing for powere there. You have to do this with the truck started. Like Blazerboy said in his EXCELENT post, there is a switch that sends power to the choke when you have oil pressure. So there should be no power when the engine is off. With engine started put the black wire on the negative terminal of the battery and the positive to the the wire going to the choke. Should read 12.6-14volts. Switch your volt meter to OHM's and with the black wire on ground again UNPLUG the wire going to the choke touch the terminal ON the choke ( if you hit the 12v while the in OHM's mode you might damage the meter). If it reads a dead short like if you touched the two leads together then the element is bad. If it doesn't change it's bad. It's been a couple years since I had one go bad and I don't recall how many ohms a good element should read. I want to say around 80 ohms but not positive on that.
    Also if you don't see 12v on that choke wire then you got some electrical problems. That carb will have a electric mixcontrol solonoide if it's the correct carb for the year of the truck. The Choke and mix solonoide are on the same electrical circuit. If you have the mix solonoid on the top of the carb on the passengerside front corner will be a terminal with a plug. One wire will join the choke wire at the oil pressure switch behind the distributor. The other wire goes to a thermo switch on the intake or water neck. Make sure that's all plugged up.
    If you have no power up there then check for blown fuses. Sometimes when the choke element is going bad it will blow the fuse. Should be marked Choke.
    If you do find the element is bad the new element will come with new screws or new rivits. If it comes with rivits then go to a hardware stor and get 3 #8 1/2 inch long sheet metal screws. Mark the housing that the element goes in so that you can install the new element the same rotation. Drill the three rivits out with a 1/8inch bit. Pay close attention when you pull the element. The spring coil has a hook bent in it at the end that engages a fork. Pay attention to what finger on the fork the spring is on.
    Just for the record. Those elelment usualy fail ever 2-3 years has been my experience. The symptoms your experiancing do sound like what it does when it fails. It's always good to do the checks before you spend $30 on a new one. Parts stores don't generaly take electrical parts back even if they a not the problem.
     
  13. Blue85

    Blue85 Troll Premium Member

    Joined:
    Jul 26, 2000
    Posts:
    9,073
    Likes Received:
    486
    Location:
    Grand Rapids area
    Re: Choke Light on Idle up

    Blazer boy,
    I was just referring to this line:
    </font><blockquote><font class="small">In reply to:</font><hr />
    There should be a little sender with three wires going to it, that tells the choke when to open

    [/ QUOTE ]

    Otherwise, your post seemed right on /forums/images/icons/smile.gif
     
  14. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Re: Choke Light on Idle up

    Oh ok, I was talking about the pressure switch. I see just what you mean though. Sorry about that /forums/images/icons/crazy.gif

    -------------

    How do you know there's a vac leak? Now if I tell you this ancient Chinese secret, you've got to promise not to tell anyone, or I'll have to kill you /forums/images/icons/smirk.gif . Get a can of WD-40, carb cleaner, or the like and spray it on the suspect area. The leak would suck in the spray and cause a change in your idle. Check ALL the vac lines and replace any suspect ones. There is going to be a sucking noise under there from the carb. I mean you got a force of 20+ inches of vacuum trying to feed over 300 cubic inches through two 1 7/32" primaries in the carburetor which are almost totally blocked off by the throttle blades at idle.
     
  15. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    Re: Choke Light on Idle up

    Grim: Thanks for the detail!! I'll have to print this out and take it home with me as I'm at work. Can't wait to go home again.


    BlazerBoy: We've tried that with the WD-40 and the it changes when we spray the driver side of the carb. That's when we changed the gasket. The gasket change helped a little but in the end, my poor carb is still giving inconsistant idle speeds. /forums/images/icons/frown.gif
    What's next?
    YOU GUYS ARE GREAT!!
     
  16. MilpitasK5

    MilpitasK5 1/2 ton status

    Joined:
    Nov 13, 2001
    Posts:
    889
    Likes Received:
    0
    Location:
    Milpitas, Ca.
    Re: Choke Light on Idle up :Update

    Well, it turns out that is was just the burnt wire and the fuse. /forums/images/icons/blush.gif But I saved this thread b/c it's going to save my K5 one day!!
    Thanks! /forums/images/icons/smile.gif
     

Share This Page