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Lack of power
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Wed Feb 13, 2019 8:09 pm    Post subject: Lack of power Reply with quote

Hi help needed!!
Car is a 1946 Austin 10 gs1
Car starts and ticks over ok, press the accelerater and it nearly cuts out ie no power.
If I slowly apply accelerater it will pick up engine speed.
It has had new points, dizzy cap, coil, condenser, plugs, ht leads and connectors and vacuum diaphragm unit. The vacuum pipe has been tested for leaks. Also I have cleaned the carb and jets and set the timing plus checked the mechanical advance mechanism in the dizzy which is free and working.
Any ideas what is wrong please.
Peter
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alastairq



Joined: 14 Oct 2016
Posts: 1085
Location: East Yorkshire

PostPosted: Wed Feb 13, 2019 8:12 pm    Post subject: Reply with quote

Air leak into the inlet manifold, downstream of the carburettor?
_________________
Dellow Mk2, 1951 built, reg 1952.
Ford Mustang coupe, 1967, 6 cylinder auto.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Wed Feb 13, 2019 8:27 pm    Post subject: Reply with quote

Thanks for the reply.
I changed the manifold gasket. Did a good clean of the mating surfaces but did notice some putting on the manifold around the exhaust aperture but thought the new gasket would be enough to deal perhaps not. I did not check to see if the surface was warped which could be causing a leak.
So will have to remove again!!
Pete
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alastairq



Joined: 14 Oct 2016
Posts: 1085
Location: East Yorkshire

PostPosted: Wed Feb 13, 2019 8:42 pm    Post subject: Reply with quote

Carburettor gasket? Vacuum take-off's leaking? Try spraying some brake cleaner[carefully] around these various gasket points whilst the engine is ticking over...if air is being drawn in, the revs should rise a bit.
Does the inlet manifold have a hot spot with the exhaust manifold?
_________________
Dellow Mk2, 1951 built, reg 1952.
Ford Mustang coupe, 1967, 6 cylinder auto.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Wed Feb 13, 2019 8:53 pm    Post subject: Reply with quote

Not sure what do you mean with the last question about the hot spot?
Have read about spraying near the manifold but never done it.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1316
Location: Above the snow line in old Monmouthshire

PostPosted: Wed Feb 13, 2019 9:06 pm    Post subject: Reply with quote

I note that you have cleaned the carb and jets. However, if the fuel supply to the carb contains sufficient fine sediment it's entirely possible for the jets to block again in a very short time. Obviously filters help to some degree, though I have my doubts about how much of the really fine stuff they actually catch.. Could you possibly rig up a clean gravity feed for testing purposes, I wonder?
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Wed Feb 13, 2019 9:11 pm    Post subject: Reply with quote

Thanks for the thought.
I suppose the clean fuel test could be done. Although I had rechecked the jets and they were clear having said that it was a month ago so could check them again.
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alastairq



Joined: 14 Oct 2016
Posts: 1085
Location: East Yorkshire

PostPosted: Wed Feb 13, 2019 11:37 pm    Post subject: Reply with quote

A hot spot, refers to the close proximity of the inlet manifold [base] to the exhaust manifold...to prevent, amongst other things, carburettor icing.
With some makes, a hot spot might consist of a hole connecting the inlet to the exhaust manifold, closed off by a thin sheet of metal. If this rusts through, then one has a tiny, but unseen , air leak into the inlet manifold.
Much will depend on the Austin's design, of which I know little...but the symptoms you describe are common enough over all designs of petrol engine.
_________________
Dellow Mk2, 1951 built, reg 1952.
Ford Mustang coupe, 1967, 6 cylinder auto.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Thu Feb 14, 2019 8:31 am    Post subject: Reply with quote

Thanks for explaining don't know if mine is like you say would have to check. My first check will be with the brake spray test I have a feeling that the gasket doesn't have a good seat.
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alastairq



Joined: 14 Oct 2016
Posts: 1085
Location: East Yorkshire

PostPosted: Thu Feb 14, 2019 2:29 pm    Post subject: Reply with quote

carb cleaner is good too...owt that is fine, and goes bang...
_________________
Dellow Mk2, 1951 built, reg 1952.
Ford Mustang coupe, 1967, 6 cylinder auto.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Rick
Site Admin


Joined: 27 Apr 2005
Posts: 20180
Location: Cheshire

PostPosted: Thu Feb 14, 2019 5:02 pm    Post subject: Reply with quote

I'd also be looking for air leaks, blocked jets, and maybe the points in case they closed up. If it's running super-lean then maybe the gauze filter in the top of the (if AC?) pump is blocked?

RJ
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Rick (OCC Admin)
Various 1920s-1960s - Austin, Morris, Commer, Dodge etc.
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47Jag



Joined: 26 Jun 2008
Posts: 1457
Location: Bothwell, Scotland

PostPosted: Thu Feb 14, 2019 7:34 pm    Post subject: Reply with quote

Peter,

You say you changed the points, did you re-check the timing? The symptoms are similar to retarded timing.

Does your carb. have an accelerator pump, that is when you press the accelerator it sprays raw petrol into the manifold. This enables the engine to pick up speed quickly.

Did the engine run alright before you started work? If it did then itís something you changed. Re-check what youíve done again.

Art
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Thu Feb 14, 2019 8:00 pm    Post subject: Reply with quote

Thanks for all the comments.

In reply to Rick clean points and had the pump off and cleaned, did clean jets but you never know with all the fiddling could be blocked again will check.

In reply to 47 jag Art yes I have done the timing like I say the engine starts ok. It does not have an accelerated pump so not that. The engine had not been running for 15 years and when I eventually got it running I think it did pick up better, like I said earlier I have changed the manifold gasket and the last port flange was pitted but I thought the gasket would take up any slight imperfections. I never checked if it was warped.

Pete
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Farmer John



Joined: 18 Feb 2010
Posts: 159
Location: Manawatu NZ

PostPosted: Thu Feb 14, 2019 9:01 pm    Post subject: Reply with quote

Hi Pete. Forget about air leaks because your engine idles, it will not idle with an air leak. The ignition system is probably good to go and you have enough compressions.
When you attempt to quickly increase engine speed the fuel delivery system breaks down suggesting the carburetor. However you must first make sure that the fuel pump is supplying sufficient fuel by removing the pipe from the carb, put the end in a container and crank the engine over on the starter. As long as there is a strong pulsing flow that is OK.
Back to the carb. It needs a thorough clean using compressed air and carb cleaner, you must clean every drilling, every orifice. The drillings sometimes show up where they end at a brass plug or you can see the casting shape in the carb body. As the butterfly opens it passes some holes in the carb bore, these are progression jets and are important for the throttle change from idle to full power so make sure of them.
That is how a gentleman would do it. Not suggesting you copy me but this is what I would have done right at the outset. Remove the air cleaner and with the engine running wrap a hand around the carb and slowly restrict the air flow but not enough to stall it then open the throttle with the other hand. Alter the restriction with your hand until it will accelerate properly. If this works then all the electrics are fine and it is definitely the carb. Sometimes it is possible to do this by using the choke but most choke flaps are applied by a spring which the engine might easily overcome. Actually, in your case it is worth a try to apply the choke and the throttle together - you never know.
John
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Austin100



Joined: 06 Nov 2018
Posts: 44
Location: Denton

PostPosted: Thu Feb 14, 2019 9:39 pm    Post subject: Reply with quote

John
Thanks for the lengthy reply well explained.
I checked the fuel pump and it squirts good so that is ok.
I will give that a try tomorrow before I relook at the manifold gasket and if it is that will have to give the carb a proper clean I only took the jets out and cleaned those and not all the drillings.
Pete
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