View Full Version : Carby queries
01-06-02, 09:24 PM
I have a single carby, twin barrel (primary and secondary system). It was acting up a little, in the sense that whenever I gave it some stick for the next 30 mins or so it would idle really high. So I got some carby cleaner in there, and now it won't idle at all.
Looked through the workshop manual, went through the troubleshooter, and have since replaced fuel lines, fuel filter, plugs, distributor rotor and cap. I need to replace my points, they are pretty bad. Neighbour looked at it and recons the carby is stuffed too, something is stuck in it (you can hear it choking).
Now, my secondary system doesn't appear to be working at all. It's grotty inside, and even when revving hard it doesn't open. I'm guessing it's stuffed. What makes it open? Could there be a cable or something that has come undone?
And how can I clean the primary system so that the car will idle again? I've used a lot a lot of carby cleaner but to no avail.
How much are these old things anyway? $50 from the wreckers?
01-06-02, 10:05 PM
You should be able to pick up another carbie for about 20 bucks..
It might be that they throttle lever isn't returning fulling and it sticking...
It might also be something to do with the temperature compensation thingo... on the side of the carbie..
Basically when I had carbie troubles. I bought another one, and built a good one out of both of them..
02-06-02, 12:44 AM
If you've got a workshop manual, it should tell you how to strip down, clean, and reassemble the carby... Go down to repco and buy a rebuild kit for it (about $30) which gives you new parts/gaskets etc for it, and just follow the workshop manual. It should only take about 1 1/2 hours to strip down and reassemble... however, if the thingies inside (****ed if i can remember what they're called @ midnight) need rebushing, you'll have to outsource to a carby specialist... this takes all of 10 minutes for them to do, and costs about $20 if i remember correctly.... so approx $50 and you'd have an as-new carby. Then the only trouble is tuning the bitch :D
what sort of car? by rowdy's comments i'm guessing a corolla? most dual throat carbs use vacuum operated secondaries, and as such, wont open by flat revving at idle.
It sounds like you have a blockage somewhere, either from crap or water. an old trick is to rev the engine to say 4 grand, and hold a rag over the carb throat while keeping the throttle wide open, until the engine dies to say 1500 - 2000 rpm, then taking the rag away, and letting it rev back up again. this produces enormous vaccum in the carb and can often clear debris from the jets or emulsion tubes. doesnt alwayts work, and if you stall it, it'll be flooded and be a bugger to start (so dont let it stall :p)
You may also have a vacuum leak, check the bushes on the throttle shaft for movement, and have a look around the manifold and carb base for suced in gaskets, and vacuum hoses for cracks.
9 out of 10 "carby" problems are not the carby.
02-06-02, 12:52 PM
Secoh.... corolla's are all I'm good for :D LOL
How would high idle when hot be caused by a blockage.. I can understand a miss or hesitation.. but not high idle..??
02-06-02, 02:02 PM
Guys' I have a few thoughts.
What if after thrashing the car the heat in the inlet manifold warped it just enough for the gasket between the inlet manifold and head to leak? Or even the carby to inlet manifold gasket? I assume the exhaust manifold is right next to the inlet manifold.
This would cause it to run a little lean and idle high.
After using the carby cleaner it might have cleaned out all the gunge that was actually helping seal the gaskets and now the leak is so bad that it won't idle.
Also toranafan might be right. If the bushes that support the throttle butterfly are worn this would let air suck in and make the idle lean and the carby cleaner might have made the leak bigger.
Usually if it is an inlet leak the car will still idle with the choke on a bit.
I found an inlet manifold leak on my old Datto 1200 by this method.
Find a piece of hose (1m of garden hose will do) and with the engine running stick one end in your ear and with the other end closely follow all around the inlet gaskets. You would hear a pulsed sucking noise where the leak is.
Just don't get too close to the carby inlet as if your brain is too small it might get sucked out through the hose :D
Hope this helps.
02-06-02, 02:43 PM
If it's a vacuum leak it shouldn't idle at all right? Sometimes (like very very once in awhile) it idles for a short while (say 30 seconds) before dying... Othertimes it either dies immediately or dies after a couple of seconds. Anyways may have a look at it again today if I'm really enthusiastic...
02-06-02, 04:01 PM
If it's a very small leak it will still idle.
The engine will idle at higher revs because of the extra air being sucked through the leak but the problem is there is no extra fuel being added to this air. This lean mixture will cause it to die after idling for a short time like you say.
When driving the car it's not a problem coz there isn't as much vacuum in the inlet manifold with the throttle open. There is also a much greater volume of air/fuel passing through the manifold so a tiny bit more air won't upset things too much.
I had this problem on another car and found the bolts that hold the inlet manifold to the head were loose. Tried tightening them all to how they should be and the car ran fine! I like easy fixes like that but they don't happen too often.
03-06-02, 10:35 AM
Hmm, maybe maybe :) Shoulda tried that I guess, instead of replacing just about everything :p
Oh well, the "pros" are having a look at it today... Cause I think I may need a new distributor or something as well, got new points yesterday and even at the highest point the gap is too close, I think the cam lobe is worn...
03-06-02, 07:55 PM
Distributor was fine, I just suck at putting points in.
All up it cost me $120 (ouch), $49 for the carby 2nd hand...
I must learn to do all this myself. Then I can save lotsa money... BTW, what is a dwell angle. They said they checked that and it was okay. But I have no idea what it is...
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