I have a 1981 GMCvandura 25 with a 350 4bbl carb. the choke.
The choke dosent work well. I cleaned it with carb cleaner but it only helped a little. I want too recheck the, air fuel,choke leanness or richness settings but cannot find the information on line to download and would like to do this quickly.Thank You for YOUR Time.
Re: I have a 1981 GMCvandura 25 with a 350 4bbl carb. the...
Its all in the idle screws, if there bad you will be chasing them every time you drive it, also the choke spring inside could be bad, if you have a that style. screw the idle in on both sides all the way in, then back out 2 and a half turns, this should be where you will run the best. adjust as needed, but that is the standard. i also run sea foam through the carb, alot better then any cleaner on the market. usr it in your fuel or try to put it in the carb, i have uesd the vacume lines to do this, but you will also have to keep the car at high idle when doing this, it will clean all of the junk and carbon out of the entire motor.
if you need more help, please be clear or the carb, and hat you have done and not done already'
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The problem is that when you have the switch in the START position, you are getting power to the ignition system, but not when in the RUN position. Most likely causes are a bad ignition switch, a faulty aftermarket alarm system [if it has one] or a bad ballest resistor wire going to the ignition coil's + terminal. You need to break out your test light and start checking to see where the fault lies.
The two products are generally the same with a couple of differences. Sometimes the intake and throttle body cleaner can be sprayed upside down to reach areas hard to get to with the can in the upright position. Some intake and throttle body cleaner products are supposed to be ok with special metals and plastics used on newer cars and trucks. You would probably be safer with intake and throttle body cleaner if the car is fuel injected.
The vacuum signal for the advance needs to come from a ported vacuum source on the carburetor, and not from manifold vacuum. Ported vacuum means little or no vacuum at idle, because the throttle plates at idle shut off the ported vacuum hole. Look for a vacuum tube coming from near the base of the carburetor.
I have no resource to find a diagram. You may need to check a repair manual that your local library might have. Or purchase a Haynes or Chilton manual for around $25. Or join a forum for older Chevy/GMC trucks; somebody there could help you, I'm sure. Good luck.
It sounds like the Idle Air Control Valve is stuck. This will give you a fixed idle it can stick at high idle or low or anywhere in between. If you take off the air cleaner you see where the air is getting sucked into a small slot or hole. spray some carb and choke cleaner in there let it sit for about 5 minutes then start the engine. spray a little at a time with the engine running till the idle comes down by itself. This should take about 2-3 minutes. If it wont come back on its own take the 2 torx screws out and remove it clean with carb and choke cleaner and replace. If it still fails it will need to be replaced. MOST of the time cleaning it will work
Is the chokeoperating properly? You say the current carb has an electric choke, so I am assuming the original carb did not have an electric choke. If that's the case, have you wired the electric choke to a power supply?
You need to rebuild the carburetor. As it is a 1 barrel its relatively easy to rebuild if you can find a kit, but it is the original carb and difficult to find parts. You may also consider buying a Holley 2 barrel carb - it will bolt right on and give you more power, and they are much more common and easier to find rebuild kits and parts. It's possible you may need an adapter plate, depending on the configuration of your intake manifold, but that will be easy to find. You can either shop online or buy from your local auto parts store or high performance shop. That old 1 barrel has had its day and I'm sure it served you well,but I think I would upgrade to a newer carb myself.You may be able to clean it out using carb cleaner spray but it would be hard to clear out that clogged jet that is causing your trouble, and then you will likely tear the gasket when you take the top off that carb.
could be your idle control motor. take it off and clean it with some carb cleaner.
to find leaks i spray a little carb cleaner near suspected areas the engine will speed up when you find one, try around manifold gaskets and vacuum lines
You can check to see if it is a fuel issue next time remove the air cleaner and shoot a squirt of carb cleaner in the throttle body if it fires right up with it running give it a little gas and squirt sperts of T.B. cleaner into the T.B. to clean any residue. Also if that works throw a bottle of gas treatment in.
The first thing i would look at here is the choke pull. Make sure that after the car starts, the choke props open. Also, as the engine warms, make sure the electric choke is opening up. If not, make sure you have 12V to the choke. If so, replace it. This should solve the problem.
But let me know if you need any further assistance, ok? We'll get it working! :)
Sounds like it's a carburetor problem. Your choke could not be working properly or maybe your accelerator pump is clogged on your carb. First check the choke though. I've even known a lot of guys that wire their choke to stay open on their race cars but don't really know how well it works since I haven't done it myself. Hope this helps. Let me know what happens.