S2a refuses to idle

S2a, 2¼ petrol, 70K miles.

I fitted a new "Zenith" pattern carb (from Craddocks) about 2000 miles ago.
Since then she has run perfectly, with plenty of power, a smooth idle hot or
cold, and economy improved from 14mpg to about 20. So far, so good.

Yesterday, the idle speed dropped to almost zero (I had it set to where the
charge light would just flicker) and today she refuses to idle at all.
Increasing the idle speed a fraction kills the engine dead. Moving the idle
mixture screw in and out makes no difference (until you take it right out,
when the engine stops, obviously). Normal speeds, the engine runs fine as
before. Nothing loose, fallen off or obviously broken, vacuum advance pipe
is in place, and I've done nothing to it except drive around. I'm guessing
either an air leak on the inlet side or a blocked idle jet, but I thought
I'd see if anyone had any bright ideas.

One other symptom, which has developed at the same time: the exhaust has
always popped a bit on a steep downhill on my way back from work, but now
it's popping regularly and loudly even slowing down for junctions. This
suggests an air leak on the exhaust side. New exhaust fitted about 2000
miles ago, but again no problems until yesterday.

Anyone put two and two together and make SQRT(25)? I'll strip and clean the
carb at the weekend otherwise, but since it was 100% OK before yesterday I
reckon it must be something silly.

Thanks

--

Rich

Pas d'elle yeux Rhone que nous

"Richard Brookman" <[email protected]> wrote in message
news:[email protected]...
> S2a, 2¼ petrol, 70K miles.
>
> I fitted a new "Zenith" pattern carb (from Craddocks) about 2000 miles
ago.
> Since then she has run perfectly, with plenty of power, a smooth idle hot
or
> cold, and economy improved from 14mpg to about 20. So far, so good.
>
> Yesterday, the idle speed dropped to almost zero (I had it set to where
the
> charge light would just flicker) and today she refuses to idle at all.
> Increasing the idle speed a fraction kills the engine dead. Moving the
idle
> mixture screw in and out makes no difference (until you take it right out,
> when the engine stops, obviously). Normal speeds, the engine runs fine as
> before. Nothing loose, fallen off or obviously broken, vacuum advance
pipe
> is in place, and I've done nothing to it except drive around. I'm
guessing
> either an air leak on the inlet side or a blocked idle jet, but I thought
> I'd see if anyone had any bright ideas.
>
> One other symptom, which has developed at the same time: the exhaust has
> always popped a bit on a steep downhill on my way back from work, but now
> it's popping regularly and loudly even slowing down for junctions. This
> suggests an air leak on the exhaust side. New exhaust fitted about 2000
> miles ago, but again no problems until yesterday.
>
> Anyone put two and two together and make SQRT(25)? I'll strip and clean
the
> carb at the weekend otherwise, but since it was 100% OK before yesterday I
> reckon it must be something silly.

Richard,
The exact thing is happening to mine except for the tickover.
I replaced the Exhaust and manifold and can see or hear no obvious leaks.
Has your water temp changed since it started Popping?Mine is running cooler
and going to reset the carb today to see if it makes a difference..

Try running the engine at fast tickover and blocking the air inlet with a
rag so it stalls to clear any blockages..

Have you recently cleaned the air filter too much oil in it may cause
this...

Adrian Ford

"Adrian Ford" <[email protected]> wrote in message
news:[email protected]...
>
> "Richard Brookman" <[email protected]> wrote in message
> news:[email protected]...
> > S2a, 2¼ petrol, 70K miles.
> >
> > I fitted a new "Zenith" pattern carb (from Craddocks) about 2000 miles
> ago.
> > Since then she has run perfectly, with plenty of power, a smooth idle
hot
> or
> > cold, and economy improved from 14mpg to about 20. So far, so good.
> >
> > Yesterday, the idle speed dropped to almost zero (I had it set to where
> the
> > charge light would just flicker) and today she refuses to idle at all.
> > Increasing the idle speed a fraction kills the engine dead. Moving the
> idle
> > mixture screw in and out makes no difference (until you take it right
out,
> > when the engine stops, obviously). Normal speeds, the engine runs fine
as
> > before. Nothing loose, fallen off or obviously broken, vacuum advance
> pipe
> > is in place, and I've done nothing to it except drive around. I'm
> guessing
> > either an air leak on the inlet side or a blocked idle jet, but I
thought
> > I'd see if anyone had any bright ideas.
> >
> > One other symptom, which has developed at the same time: the exhaust has
> > always popped a bit on a steep downhill on my way back from work, but
now
> > it's popping regularly and loudly even slowing down for junctions. This
> > suggests an air leak on the exhaust side. New exhaust fitted about 2000
> > miles ago, but again no problems until yesterday.
> >
> > Anyone put two and two together and make SQRT(25)? I'll strip and clean
> the
> > carb at the weekend otherwise, but since it was 100% OK before yesterday
I
> > reckon it must be something silly.
>
> Richard,
> The exact thing is happening to mine except for the
tickover.
> I replaced the Exhaust and manifold and can see or hear no obvious leaks.
> Has your water temp changed since it started Popping?Mine is running
cooler
> and going to reset the carb today to see if it makes a difference..
>
> Try running the engine at fast tickover and blocking the air inlet with a
> rag so it stalls to clear any blockages..
>
> Have you recently cleaned the air filter too much oil in it may cause
> this...
>
> Adrian Ford
>
>
>I reckon
It could be a bit of lint in a jet
It could be some water in the bowl
It could be you are running a bit retarded
It could be the points are sh***ed
Could be an air leak
Or any combination....

Good Luck

So Adrian Ford was, like


> Richard,
> The exact thing is happening to mine except for the
> tickover. I replaced the Exhaust and manifold and can see or hear no
> obvious leaks. Has your water temp changed since it started
> Popping?

Nope - runs cool as before.

> Mine is running cooler and going to reset the carb today to
> see if it makes a difference..
>
> Try running the engine at fast tickover and blocking the air inlet
> with a rag so it stalls to clear any blockages..

Haven't heard this one for a long time - good idea, I'll give it a try.
(Except that fast tickover is what it won't do. I can set the tickover high,
start it in the cab and it runs fast, but by the time I get round to the
business end it has died again.)

>
> Have you recently cleaned the air filter too much oil in it may cause
> this...

Yes, recent full service before an offroading weekend, but that was back in
January. Has run fine until a couple of days ago.
>
> Adrian Ford

Thanks for the ideas.

--

Rich

Pas d'elle yeux Rhone que nous

In message <[email protected]>, Richard Brookman
<[email protected]> writes
>So Adrian Ford was, like
>
>
>> Richard,
>> The exact thing is happening to mine except for the
>> tickover. I replaced the Exhaust and manifold and can see or hear no
>> obvious leaks. Has your water temp changed since it started
>> Popping?
>
>Nope - runs cool as before.
>
>> Mine is running cooler and going to reset the carb today to
>> see if it makes a difference..
>>
>> Try running the engine at fast tickover and blocking the air inlet
>> with a rag so it stalls to clear any blockages..
>
>Haven't heard this one for a long time - good idea, I'll give it a try.
>(Except that fast tickover is what it won't do. I can set the tickover high,
>start it in the cab and it runs fast, but by the time I get round to the
>business end it has died again.)
>
>>
>> Have you recently cleaned the air filter too much oil in it may cause
>> this...
>
>Yes, recent full service before an offroading weekend, but that was back in
>January. Has run fine until a couple of days ago.
>>
>> Adrian Ford
>
>Thanks for the ideas.
>
I have had some trouble with idle speed on my s3.
Set everything up lovely and it would run fine then suddenly (usually
after being banged around on a forestry road) it would run unevenly.
Blamed it on all sorts of stuff.
It has a new exhaust, new dizzy and no apparent air leaks.
What I did notice while playing with the mixture screw was a very small
sound coming from the crank case breather valve near the carburettor.
On inspection I discovered the rubber diaphragm therein has been
replaced with a circle of inner tube! This didn't look as though it
would seal too well and would provide an entry point for air in the
inlet tract.
Removing the plugs indicated that it had been running pretty lean.
Might be worth checking this. (If s2a's have such thing)

Does anyone know where I could get a diaphragm online for this thing?
The part number for the whole unit is rtc6855 but I don't seem to be
bale to find the number for the diaphragm itself.

--
Mark Roberts

Sounds like points to me. Re-gap or replace.

HTH, Roy.

"Adrian Ford" <[email protected]> wrote in message
news:[email protected]...
>
> "Richard Brookman" <[email protected]> wrote in message
> news:[email protected]...
>> S2a, 2¼ petrol, 70K miles.
>>
>> I fitted a new "Zenith" pattern carb (from Craddocks) about 2000 miles
> ago.
>> Since then she has run perfectly, with plenty of power, a smooth idle hot
> or
>> cold, and economy improved from 14mpg to about 20. So far, so good.
>>
>> Yesterday, the idle speed dropped to almost zero (I had it set to where
> the
>> charge light would just flicker) and today she refuses to idle at all.
>> Increasing the idle speed a fraction kills the engine dead. Moving the
> idle
>> mixture screw in and out makes no difference (until you take it right
>> out,
>> when the engine stops, obviously). Normal speeds, the engine runs fine
>> as
>> before. Nothing loose, fallen off or obviously broken, vacuum advance
> pipe
>> is in place, and I've done nothing to it except drive around. I'm
> guessing
>> either an air leak on the inlet side or a blocked idle jet, but I thought
>> I'd see if anyone had any bright ideas.
>>
>> One other symptom, which has developed at the same time: the exhaust has
>> always popped a bit on a steep downhill on my way back from work, but now
>> it's popping regularly and loudly even slowing down for junctions. This
>> suggests an air leak on the exhaust side. New exhaust fitted about 2000
>> miles ago, but again no problems until yesterday.
>>
>> Anyone put two and two together and make SQRT(25)? I'll strip and clean
> the
>> carb at the weekend otherwise, but since it was 100% OK before yesterday
>> I
>> reckon it must be something silly.
>
> Richard,
> The exact thing is happening to mine except for the tickover.
> I replaced the Exhaust and manifold and can see or hear no obvious leaks.
> Has your water temp changed since it started Popping?Mine is running
> cooler
> and going to reset the carb today to see if it makes a difference..
>
> Try running the engine at fast tickover and blocking the air inlet with a
> rag so it stalls to clear any blockages..
>
> Have you recently cleaned the air filter too much oil in it may cause
> this...
>
> Adrian Ford
>
>
>

mark wrote:

> Does anyone know where I could get a diaphragm online for this thing?
> The part number for the whole unit is rtc6855 but I don't seem to be
> bale to find the number for the diaphragm itself.

I've seen 360635 quoted as the diaphragm part number. I cannot confirm
the accuracy of that information.

Sounds like a classic case of Zenith Warp to me, try filling in the jet as
recommended
http://www.fourfold.org/LR_FAQ/Series/FAQ.S.carb.zenith.fix.html

Karen

"Richard Brookman" <[email protected]> wrote in message
news:[email protected]...
S2a, 2¼ petrol, 70K miles.

I fitted a new "Zenith" pattern carb (from Craddocks) about 2000 miles ago.
Since then she has run perfectly, with plenty of power, a smooth idle hot or
cold, and economy improved from 14mpg to about 20. So far, so good.

Yesterday, the idle speed dropped to almost zero (I had it set to where the
charge light would just flicker) and today she refuses to idle at all.
Increasing the idle speed a fraction kills the engine dead. Moving the idle
mixture screw in and out makes no difference (until you take it right out,
when the engine stops, obviously). Normal speeds, the engine runs fine as
before. Nothing loose, fallen off or obviously broken, vacuum advance pipe
is in place, and I've done nothing to it except drive around. I'm guessing
either an air leak on the inlet side or a blocked idle jet, but I thought
I'd see if anyone had any bright ideas.

One other symptom, which has developed at the same time: the exhaust has
always popped a bit on a steep downhill on my way back from work, but now
it's popping regularly and loudly even slowing down for junctions. This
suggests an air leak on the exhaust side. New exhaust fitted about 2000
miles ago, but again no problems until yesterday.

Anyone put two and two together and make SQRT(25)? I'll strip and clean the
carb at the weekend otherwise, but since it was 100% OK before yesterday I
reckon it must be something silly.

Thanks

--

Rich

Pas d'elle yeux Rhone que nous

On or around Sat, 26 Mar 2005 12:51:45 +1000, "Karen Gallagher"
<[email protected]> enlightened us thusly:

>Anyone put two and two together and make SQRT(25)? I'll strip and clean the
>carb at the weekend otherwise, but since it was 100% OK before yesterday I
>reckon it must be something silly.

could also be a leak on the inlet manifold, making for incorrect mixture at
idle.

or a blocked idle jet, maybe.
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"The great masses of the people ... will more easily fall victims to
a great lie than to a small one" Adolf Hitler (1889 - 1945)
from Mein Kampf, Ch 10

So Austin Shackles was, like

> On or around Sat, 26 Mar 2005 12:51:45 +1000, "Karen Gallagher"
> <[email protected]> enlightened us thusly:
>
>> Anyone put two and two together and make SQRT(25)? I'll strip and
>> clean the carb at the weekend otherwise, but since it was 100% OK
>> before yesterday I reckon it must be something silly.
>
> could also be a leak on the inlet manifold, making for incorrect
> mixture at idle.
>
> or a blocked idle jet, maybe.

Thanks to everyone for the replies. First free weekend in months, so I
planned to have a good look yesterday. Went for a short run first to do a
few errands, and - ding - it's cured itself. Warmed it up, reset the idle
mixture and speed, and it's as good as new. Blocked jet looks like the most
likely contender. Coconut to those who suggested that. (I've filed all the
other ideas for future reference. Cheers.)

Land Rovers! Doh. Love 'em.


--

Rich

Pas d'elle yeux Rhone que nous