Carb Blockage

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pbar
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Carb Blockage

Postby pbar » Tue Aug 21, 2018 8:10 pm

I have some crud in the carb's idle circuit, causing the car to stall when idle. Usually when this happens I blow compressed air through the idle circuit (method recommend by Weber), and all is fine. However, after a few miles of perfect running it happens again. I am assuming that there is some stubborn crub in there which I am only temporary 'moving' which after a while works it's way back into the circuit again.

Martin (Bug) told me of a method once, whereby you take the air filter off and place your hand over the top of the carb, which sucks/forces the crud out. I never tried it at the time as the compressed air method worked. But, is that bascially all I do, take the air filter off and with the engine idling cover the carb with my palm for a few seconds? Just checking before I wreck something :)

Any other carb crud removal methods appreciated too. Thanks.

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Re: Carb Blockage

Postby Peter-S » Tue Aug 21, 2018 9:26 pm

That takes me back. My old man had a Viva that he used to do that to as a sort of choke mechanism when trying to start it from under the bonnet (you could in those days) as it was sometimes a real pita! But yes as you say, filter off and hand on the top. A 'few seconds' will probably stall the engine as you will be starving it of air. It's more of a quick on then off as the engine falters.
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Re: Carb Blockage

Postby Paul G » Tue Aug 21, 2018 9:32 pm

It does sometimes work Paul and is also a good way of getting fuel up from fuel pumps which are not priming. You will probably have to raise the revs a bit or the engine will just stall when the venturi are blocked.

There is however a slight risk that whatever's causing the stalling will be sucked further into the idle circuit in which case you will have to remove the carb and back blow it to pop the crud out. Might pay to clean out the float chamber too.

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Re: Carb Blockage

Postby pbar » Wed Aug 22, 2018 8:46 am

Thank you guys, will hopefully have a go tonight.

Whilst looking around the net for info some people recommend blowing through the idle circuit with WD-40 (using the thin straw) or carb cleaner. Sounds like that could be inviting problems though to be honest.

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Re: Carb Blockage

Postby pbar » Thu Aug 23, 2018 6:07 am

Goodness it gives a big suck doesn't it (insert Carry On joke here). Didn't realise there was so much force being drawn into the carb. Good job I had my palm flat or I could have disappeared in there. Did as suggested and held the revs high whilst covering the top for a couple of seconds, two or three times. Didn't stall at all after doing that, so hopeful it has cleared it, idles smooth and steady. In case anyone else reads this and wants to try it, I wore a heat resistant glove, you never know!

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Re: Carb Blockage

Postby 340truck » Thu Aug 23, 2018 4:35 pm

Do the maths....at 1000rpm the engine sucks in 15 ltrs of air per second, through an aperture 32 mm wide. Thats why it tries to pull you in!
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Re: Carb Blockage

Postby pbar » Thu Aug 23, 2018 5:40 pm

340truck wrote:Do the maths....at 1000rpm the engine sucks in 15 ltrs of air per second, through an aperture 32 mm wide. Thats why it tries to pull you in!


When you read it like that, then yes, I get it! :)

You still in contact with Martin (Bug)? If so please tell him thanks, he gave me the initial advice. And that I hope he comes back here one day.

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Re: Carb Blockage

Postby pbar » Thu Oct 11, 2018 6:20 am

Still having trouble with this. After I blow compressed air through the idle circuit, or use the hand over the carb whilst revving method, the car is fine for a couple of journeys but the cutting out at idle creeps back in.

I will take the top off the carb later, as the top gasket has a slight leak so that needs doing. Whilst it's off I'll clean everything that I can, all jets out, float bowl, etc. and again blow air through all the apertures.

Anything else I might do whilst it's off?

Also, is it common practice to use gasket sealant on the carb top gasket, or just put it on dry.

Thanks :)

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Re: Carb Blockage

Postby Peter-S » Thu Oct 11, 2018 8:40 am

pbar wrote:.

Anything else I might do whilst it's off?

Also, is it common practice to use gasket sealant on the carb top gasket, or just put it on dry.

Thanks :)


Take the idle jets out from the screw housings and check them. There should be a rubber seal on each housing, perhaps they are starting to perish.
Have you replaced the filter under the big brass inlet nut?
Probably also worth changing the float needle and its housing if you haven't already.
Gasket I believe goes on dry
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Re: Carb Blockage

Postby pbar » Thu Oct 11, 2018 8:47 am

Thank you Peter. Yes I shall check all those. The carb filter looks ok.

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Re: Carb Blockage

Postby Jasonmarie » Thu Oct 11, 2018 12:45 pm

I have never done a overhaul on the Carb , as this is something I would love to try out , funny in another Link this is where that ultrasonic cleaning machine would be of help .

Strange it’s ok for a few runs then plays you up Paul , hope you get it sorted
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Re: Carb Blockage

Postby pbar » Thu Oct 11, 2018 12:49 pm

Jasonmarie wrote:I have never done a overhaul on the Carb , as this is something I would love to try out , funny in another Link this is where that ultrasonic cleaning machine would be of help .

Strange it’s ok for a few runs then plays you up Paul , hope you get it sorted


Thanks Jason :) These carbs are absolutely fascinating things when you get into it, total genius, they really are. I am assuming that the crud simply moves around when I have previously blown through the idle passages, and moves back again over a short time.

The idle circuit is fed by the main circuit, and it is this main circuit which you cannot get to until the top is off. So I hope that by cleaning it out it will sort it.

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Re: Carb Blockage

Postby Jasonmarie » Thu Oct 11, 2018 12:55 pm

Yes that does make sense Paul , in the old days I remember people putting there hand over the top so it would suck and they would Rev the engine and removed there quick to get the dirt out , Peter will know as I don’t know if it was like a egg white in the Radiator trick.
Also soaking Redex down the carb over night then when you started up it was like a think fog . :lol:
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Re: Carb Blockage

Postby pbar » Thu Oct 11, 2018 2:12 pm

Just have a read on some of the earlier posts on this thread Jason, the hand on the carb trick was mentioned, and done :)

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Re: Carb Blockage

Postby pbar » Fri Oct 12, 2018 7:55 pm

Well I took the top off and had all the jets out, cleaned the passage ways, etc.

Put it back toegther and it's still the same unfortunately. Cut out on idle several times on the first drive.

Anyone know of anything else I could try to fix this please? The rev counter at idle isn't very steady, wavering a couple of mm either way, if that gives a clue. Other than that there isn't any other unusual behaviour, but it just randomly cuts out when idling and/or coasting to a stop.

Thanks.

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Re: Carb Blockage

Postby Jasonmarie » Fri Oct 12, 2018 8:54 pm

Was wondering how things worked out for you I guess you have adjusted the idle , but let’s step back and think that all is ok with the carb as the Rev counter should not be waving and that sounds more like a faulty condenser ? If you have a spare give it try . But I can’t remember if you have the autospark set up where you don’t have a condenser .
Just a thought as it should have made it a little better with what you have done .
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Re: Carb Blockage

Postby pbar » Fri Oct 12, 2018 9:52 pm

Thanks for your input Jason. Funnily enough, my good friend Steve (stevemarl on here), has also suggested it could be ignition related. Now that you have mentioned condenser also, I think I shall try that tomorrow, as I do have a new spare. Here's hoping!

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Re: Carb Blockage

Postby Jasonmarie » Fri Oct 12, 2018 10:42 pm

Fingers crossed it’s that easy . :beer:
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Re: Carb Blockage

Postby pbar » Sat Oct 13, 2018 2:19 pm

Well I tried another condensor, and the problem remains unfortunately. Still cutting out on idle (after a few miles/warmed up, but once it does it, it will then do it again and again), and rev counter slightly erratic.

Think I will try the coil next.

Any other suggestions more than welcome. Thanks.

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Re: Carb Blockage

Postby Jasonmarie » Sat Oct 13, 2018 5:07 pm

I am sorry to here that as I was just wondering . My coil did breakdown this year and we had been driving for a good hour when I got stuck in traffic and it felt like it was jumping after a new coil it fixed the problem .
Trouble is we could suggested so many things as fuel pump , electrical , and back to your original thought .
Keep us posted that’s you and Dan having problems .

Just one last thought and this happened to my old Capri what turned out to be a exhaust valve that needed adjusting as it was way out ? As thet jump about like mad and got worse when hot .

All the best and we will or you will get there .
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