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Suddenly running rich.
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Tue Feb 28, 2017 3:33 pm    Post subject: Suddenly running rich. Reply with quote

So, Armstrong Siddeley, pair of Zenith WIA's. Car's not been run for over a year, but I've been occasionally starting it and just getting oil up but not for more than a minute at a time ( no coolant)

It has however started pretty readily, even after months without having done so.

The other day, restored the coolant system, new starter motor, now plugs, ....started fine but fuel coming out of manifold overflow. Removed ( front ) carb bowl top....gasket tatty... ordered new gasket set. Replaced front carb top gasket and replaced top...rear carb, and thus choke cable setting undisturbed.

Topped up the gallon of regular unleaded in the tank with two gallons of Super

Now....the car won't start with a squirt or EasyStart? After which is start ok ...and settle down to easy rythm...but...seems to me to come off choke rather quickly...fully off choke after a minute even though it's about 3-5C in the garage just now!!!

Once warm it'll rev freely but only if the initial thottle take up is gentle...sharp opening throttle kills it. .. feels like it's flooding.

What have I done to it t osuddenly make it APPEAR rich.

Removed number 1 and 6 plugs and they look sooty.. but both the same suggesting that both carbs are doing the same thing.

NOW .. I've not touched the ignition and I don't have a strobe...but if it's been set to factory settings and it was therefore out with unleaded...would it be so far out know with super that it'd not start easily and not burn properly.

I'm going to try to ascertain what the ignition advance is next time I'm in the garage but I though I'll try advancing the ignition...despite the fact that the guy from Burlen saying I should retard the ignition relative to factory settings?
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'60 Armstrong Siddeley Star Sapphire
'80 Reliant Scimitar
'47 Jaguar MKIV --- in bits!!!!
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alastairq



Joined: 14 Oct 2016
Posts: 1294
Location: East Yorkshire

PostPosted: Tue Feb 28, 2017 6:54 pm    Post subject: Reply with quote

Quote:
Once warm it'll rev freely but only if the initial thottle take up is gentle...sharp opening throttle kills it. .. feels like it's flooding.


This is a sign that the acceleration pump isn't doing its job...the dying is due to the sudden weakening of the mixture as the throttle is snapped open.
Looking down the venturi[s], with engine off, if throttle linkage is snapped open, is there a squirt of fuel going down the carb throats? If not, then the accelerator pumps on the side of the carbs needs looking at? {Blocked, or diaphragms have small hole?]


Is choke automatic? If so, is it opening at the right pace?
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Tue Feb 28, 2017 9:21 pm    Post subject: Reply with quote

Hmmm .... actually looking down the barrel of the carb and opening ther throttle seems to indicate that there's a hell of a lot of fuel rather than not enough....honestly, the second I pull the throttle there's petrol hosing in to the venturi....not in a nice atomised spray either ....just bloody great gobs of the stuff.

It's a manual choke and indeed it looks like I've upset something ... today I realised the choke would close a fraction further ...completely closing the choke flap ( I would have thought it'd need a slight gap?) ... having done that it did start without EasyStart.

I'm still wonderinf about ignition timing too...but established this evening that the dizzy appears jammed and won't rotate!!
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'80 Reliant Scimitar
'47 Jaguar MKIV --- in bits!!!!
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peter scott



Joined: 18 Dec 2007
Posts: 6177
Location: Edinburgh

PostPosted: Tue Feb 28, 2017 10:30 pm    Post subject: Reply with quote

Is it not the case that in these fixed jet Zeniths the choke flap has its spindle offset such that air flow will tend to open it due to the larger surface area on the side that tends to open it. I think there is also an element of spring loading between the choke control and the flap so the engine suction opens it against the spring.

Peter
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Tue Feb 28, 2017 11:39 pm    Post subject: Reply with quote

Quote:
I'm still wonderinf about ignition timing too...but established this evening that the dizzy appears jammed and won't rotate!!


Check the points gap. too close will retard the timing.

Art
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Wed Mar 01, 2017 8:37 am    Post subject: Reply with quote

Yup, next up is chk ignition ...but ... I tried last night to turn the engine over by hand (it's automatic )and failed! there's no access to the front pulley and no starter handle....hmmm

Also, as if that wasn't enough ...the dizzy is jammed and won't rotate!!!

I've got a full day in the garage tomorrow...I'll see what can be achieved.
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'47 Jaguar MKIV --- in bits!!!!
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