classic car forum header
Classic cars forum & vehicle restoration.
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Register     Posting Photographs     Privacy     F/book OCC Facebook     OCC on Patreon

Jaguar XK140 Carb Help
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> All our old cars, vans, lorries etc
Author Message
TM8



Joined: 24 Feb 2013
Posts: 53
Location: Pretoria, South Africa

PostPosted: Thu Sep 11, 2014 6:31 pm    Post subject: Jaguar XK140 Carb Help Reply with quote

Hi,
Need some assistance I am trying to help a new owner of a Jaguar XK 140. The Car backfired and set alight after visiting the Carb Specialist need to say the wiring and paint work are now damaged.
I need help with the Wiring up of the Thermostatic switch as well as the thermo solenoid assembly. Some wires go to the coil which side positive and which negative.
We don't want to try the Carb specialist again after the disaster.
I am going to go through the two carbs and check they are done up correctly and check for blockages etc. First I will sort out the reason for the backfire. Any help on checking the setting of the Carbs?
How to check the Thermo side is working?

Maybe if some one has a photo to share of this area so I can follow through I think maybe the one Carb flooded and landed up igniting through the Distributor or coil not quite sure only assuming now.
Regards
Trevor
Back to top
View user's profile Send private message
Old Wrench



Joined: 23 Dec 2013
Posts: 226
Location: Essex and France

PostPosted: Fri Sep 12, 2014 9:49 pm    Post subject: Reply with quote

The SU carburettors used on most Jags of this period used a separate starting carb or more correctly an auxilliary carburettor.

When cold the thermostatic (bi-Metal) switch enabled (powered up) the starting carb solenoid, lifted the piston, which simply allowed neat petrol into the inlet manifold.

The inlet manifold should have a drain pipe: these often blocked, meaning neat petrol being retained in the manifold. One cough and that could well be the reason for the fire. Backfires are normally caused by very weak mixture, faulty condenser, air leaks between carburettors and manifold and/or manifold and head; poor valve seats, and/or incorrect valve timing and distributor timing.

The timing chain on the Jaguar XK engine often wore, as did the Reynolds hydraulic chain tensioner. A nasty slapping noise at the front of the engine would be obvious.

These auxilliary starting carbs were notoriously unreliable!

Usual practice was to re-wire the solenoid to a dash switch, to allow manual choke on/choke off.

Setting up SU carbs is quite simple.

Firstly, disconnect the linkage between the carburettor butterflies (throttle).

With the engine warm, and air cleaner removed, gently lift the dashpot piston slightly; if the engine stalls or "hunts" enrichen the mixture by simply opening the jet carrier (by unscrewing the brass jet holder at the bottom). Mixture is correct when the engine revs increase slightly and then settle back down. Repeat for other carb/s.

Next, listen with a tube placed just into the intake orifice (the bit the air cleaner mates too). Balance the "hiss" to sound identical for both/all carburettors.

Open or close each carburettor's throttle screw to adjust vacuum depression (hiss).

You can use a a carb balancer for this: correctly called a depression meter.

e.g. http://www.scparts.co.uk/sc_en/synchrontester-22629.html

http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=10783

Once the balance is correct, tighten the throttle linkage between the carbs.

This should assist you:

http://sucarb.co.uk/technical-chokes-thermos-auxiliary-enrichment
Back to top
View user's profile Send private message
TM8



Joined: 24 Feb 2013
Posts: 53
Location: Pretoria, South Africa

PostPosted: Sun Sep 14, 2014 7:47 am    Post subject: Thanks Reply with quote

Thanks for the help.
Will check for blockages and read through the literature.
Regards
Back to top
View user's profile Send private message
47Jag



Joined: 26 Jun 2008
Posts: 1480
Location: Bothwell, Scotland

PostPosted: Sun Sep 14, 2014 10:19 am    Post subject: Reply with quote

Trevor,

I'm guessing that the engine didn't have air filters/cleaner fitted. I don't think it would have caused a lot of damage if it had.

Art
Back to top
View user's profile Send private message
peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Sun Sep 14, 2014 12:43 pm    Post subject: Reply with quote

Hi Trevor,

This might help with setting up the starting carb.

http://www.nostalgiatech.co.uk/New%20page%2018.htm

The wiring is simple. The power from the ignition switch connects to one side of the solenoid (doesn't matter which side) and the other side connects to the thermal switch.

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon


Last edited by peter scott on Sat Apr 09, 2016 8:08 am; edited 1 time in total
Back to top
View user's profile Send private message Visit poster's website
Old Wrench



Joined: 23 Dec 2013
Posts: 226
Location: Essex and France

PostPosted: Sun Sep 14, 2014 7:42 pm    Post subject: Reply with quote

Lovely pictures on your site, Peter: and a lovely car, too.

My late father ran SS Jags through the late 30s and the war (would you believe with a gasbag on the roof!); and in the late 40s switched to a Mk V saloon. And thereafter to a succession of Mark VIIs and then a Mk. IX.

And thereafter, after a mini-flirtation with the then new Standard Vanguard, a MKII.

Which was probably where I gained my own love of Jags........

Nothing quite a dose of nostalgia to promote a big.S I G H.
Smile
Back to top
View user's profile Send private message
peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Sun Sep 14, 2014 8:44 pm    Post subject: Reply with quote

Thanks OW. If you have any photos of your father's cars I would love to see them and I'm sure others woul welcome them too.

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon
Back to top
View user's profile Send private message Visit poster's website
Old Wrench



Joined: 23 Dec 2013
Posts: 226
Location: Essex and France

PostPosted: Sun Sep 14, 2014 9:36 pm    Post subject: Reply with quote

I do have a picture of Dad's wartime SS, Peter, replete with gasbag on the roof.

Trying to find the time to sort out zillions of of photos from my late mother in law and my mother who passed away only a few years ago......

I also have a picture of my wife's uncle's GN sports car, dating back to the late 1920s or early 1930s: quite a story with this one!

As always, it is time.

Has always amused me, BTW, how Bill Lyons changed the name from SS (Swallow Sideacar) to Jaguar, post WWI since the connotations of "SS" were probably not the best selling point thereafter!

Williams Lyons: one of my heroes; as was "The Jag" in Coventry.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> All our old cars, vans, lorries etc All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
OCC Merch link
Forum T&C


php BB powered © php BB Grp.