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Austin A35 chugging
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Richard H



Joined: 03 Apr 2009
Posts: 2142
Location: Suffolk

PostPosted: Sat Apr 25, 2009 8:36 am    Post subject: Austin A35 chugging Reply with quote

Well, this is a problem with my A35 restoration project, although up to about 3 weeks ago I was using it everyday. The problem started about December time. When you start it on the choke from cold, the engine chuggs and sounds like a V8! If you sit and rev it for about 7-8 seconds it clears. It seems to be temperature related?
I have changed the plugs, points, rotor arm and condenser but the problem continues. I was reminded of this as I got it out of the garage yesterday and I don't want it to be off the road forever Crying or Very sad Help!
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1987 Austin Maestro 1.3 L
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Rick
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Joined: 27 Apr 2005
Posts: 21127
Location: North-west UK

PostPosted: Sat Apr 25, 2009 9:23 am    Post subject: Reply with quote

So its fine after those first few seconds of running from cold? how is the carb mixture - too rich maybe, any smoke?

R
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Various 1920s-1960s - Austin, Morris, Commer, Dodge etc.
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Richard H



Joined: 03 Apr 2009
Posts: 2142
Location: Suffolk

PostPosted: Sat Apr 25, 2009 9:40 am    Post subject: Reply with quote

Thanks for the quick reply Rick,

Its fine after the first few seconds and chugs for longer depending on how cold the engine is. Yes it does smell slightly rich but then its running on choke so I thought that was normal. There is no excessive smoke.
The car has an original type Zenith fitted which has done about 10,000 miles. I haven't touched the mixture control at all, so I might have a fiddle with it.

Thanks again
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1935 Standard Twelve
1953 Austin A40 Somerset
1958 Austin A55 Cambridge
1959 Austin A35
1980 Vauxhall Royale 2.8 auto
1987 Austin Maestro 1.3 L
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Richard H



Joined: 03 Apr 2009
Posts: 2142
Location: Suffolk

PostPosted: Sat Apr 25, 2009 9:45 am    Post subject: Reply with quote

Oh and by the way there is no smoke at all (maybe a tiny bit Wink ) and it doesn't smell rich at all - when it's running without choke.

Thanks
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1935 Standard Twelve
1953 Austin A40 Somerset
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1959 Austin A35
1980 Vauxhall Royale 2.8 auto
1987 Austin Maestro 1.3 L
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peter scott



Joined: 18 Dec 2007
Posts: 6208
Location: Edinburgh

PostPosted: Sat Apr 25, 2009 9:54 am    Post subject: Reply with quote

Rick is correct to suggest that it's just running on too rich a mixture but I suspect that the chugging you describe is just normal behaviour for an A35.

The carburettor is just a simple downdraft with a butterfly valve operated from the choke control. It is unlikely that it is providing a richer mixture than was originally intended. The answer is to start on full choke then push the knob in a bit until it runs smoothly. Don't expect it to be as well controlled as a modern fuel injected car where you are unaware of whether it is starting cold or hot.

The only adjustable mixture control is to regulate the mixture at tick over when the engine is at normal temperature. This should not be used to alter behaviour for cold starting. There may be an adjustment for fast idle.
This doesn't alter the mixture but simply sets the tick over speed a little higher when you pull the choke out. Using part choke should permit you to operate the fast idle without actually enrichening the mixture.

HTH

Peter
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Last edited by peter scott on Sat Apr 25, 2009 10:12 am; edited 2 times in total
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Richard H



Joined: 03 Apr 2009
Posts: 2142
Location: Suffolk

PostPosted: Sat Apr 25, 2009 9:58 am    Post subject: Reply with quote

Thanks Peter, but actually it chugs whichever position the choke is in - if it is pushed in it simply chugs slower, at slower revs. I know it isn't normal for an A35 as I was using it for about six months before it started doing this. I also have another A35 which runs pefectly.

Thanks in anticipation,
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1935 Standard Twelve
1953 Austin A40 Somerset
1958 Austin A55 Cambridge
1959 Austin A35
1980 Vauxhall Royale 2.8 auto
1987 Austin Maestro 1.3 L
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peter scott



Joined: 18 Dec 2007
Posts: 6208
Location: Edinburgh

PostPosted: Sat Apr 25, 2009 10:03 am    Post subject: Reply with quote

Hi Rich,

Take the air filter off and look at the choke butterfly when you pull out the choke. I think it should be possible to have part choke to give fast idle without the butterfly closing off much. Also compare with what happens in your other car.

Peter
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1939 SS Jaguar 2 litre saloon


Last edited by peter scott on Sat Apr 25, 2009 10:05 am; edited 1 time in total
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Rick
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PostPosted: Sat Apr 25, 2009 10:04 am    Post subject: Reply with quote

might be worth blowing some air through the jets in the carb, in case one of them is partially blocked?

Rick
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Richard H



Joined: 03 Apr 2009
Posts: 2142
Location: Suffolk

PostPosted: Sat Apr 25, 2009 10:08 am    Post subject: Reply with quote

Thanks Peter and Rick,

I'll have a look at the carb today and try both your suggestions. Your knowledge really is invaluable to me! Very Happy

Thanks again
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1935 Standard Twelve
1953 Austin A40 Somerset
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1959 Austin A35
1980 Vauxhall Royale 2.8 auto
1987 Austin Maestro 1.3 L
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buzzy bee



Joined: 23 Nov 2007
Posts: 3397
Location: South Cheshire

PostPosted: Sat Apr 25, 2009 11:07 am    Post subject: Reply with quote

Hi

You probably know this but if a jet is blocked air sometimes won't clear it if it is only partially blocked, so you can sometimes carefully clear them with a single wire from a wire brush, if the jet is big enough.

Cheers

Dave
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1254
Location: Nottingham

PostPosted: Sat Apr 25, 2009 11:11 am    Post subject: Reply with quote

It will ruin the jet though - use a nylon bristle from a tooth brush. If that does not work renew the jet if is blocked
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buzzy bee



Joined: 23 Nov 2007
Posts: 3397
Location: South Cheshire

PostPosted: Sat Apr 25, 2009 12:20 pm    Post subject: Reply with quote

Phil - Nottingham wrote:
It will ruin the jet though - use a nylon bristle from a tooth brush. If that does not work renew the jet if is blocked


Hi

Hasn't hurt any of the ones I have done.

Also a good way to clean out nozzles.

Be careful and you will be fine, if you are not confident in doing it then use a bristle.

Cheers

Dave
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peter scott



Joined: 18 Dec 2007
Posts: 6208
Location: Edinburgh

PostPosted: Sat Apr 25, 2009 1:13 pm    Post subject: Reply with quote

Hi Rich,

I think that jet blockage is much more likely to cause a weaker mixture rather than a richer one so I suspect this is not your problem.

One other thing to check is the mechanism of the choke butterfly. Zenith carbs have various methods to reduce mixture strength when you rev the engine. In your case I think it will either be a hole in the butterfly that has a spring loaded plate covering it or it will have a butterfly where the spindle is offset from the centre. In the first case the spring loaded plate opens in response to the increased passage of air when you rev up. In the second type the choke control acts on the butterfly spindle through a spring such that the increased airflow on reving is able to push the larger side and partially open the butterfly valve. Check that with the choke pulled out you are able to easily open the butterfly valve against its spring. It should just open without being sticky.

Peter
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