XJ6 & XJ12 Series I, II & III 1968-1992

front carbie not drawing air

 
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Old 10-09-2014, 02:42 PM
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Default front carbie not drawing air

Hi all, set the static timing of the car -- engine runs sooooooo much better -- and turned to tune the carbies only to discover the back works great but the front doesn't draw air at all, and the piston is a bit sticky in comparison to the one nearest the bulkhead.

Any thoughts why it wouldn't draw air? Is this related to the piston or do I have two issues to solve?

Thank you!

Graham
 
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Old 10-09-2014, 02:48 PM
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Are they SU or strombergs?
Dont know a whole lot about the strombergs but its lilkely almost the same, the piston has to move up and down freely with oil as a dampner, engine vacuum is what operates teh piston and when the piston rises it pulls the needle up and more fuel goes in! thats kinda it, in a simplified manor anyways!
 
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Old 10-09-2014, 04:25 PM
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Thanks so much. Strombergs.

If the car had a vacuum issue it would affect both, no? The back carbie draws air really nicely. Am I looking at a fault in the carbie?

Maybe a perforated diaphragm? I'll open it tomorrow and take a look at that... thinking out aloud here.
 
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Old 10-09-2014, 04:29 PM
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Originally Posted by Darrenmb View Post
Are they SU or strombergs?
Originally Posted by Series1fan View Post
Should have added: I have the Stromberg carbies, with the stock US emissions set-up.
Hi Graham, maybe you could add some details of your car to your signature to help get the right answers to your questions.
Here is link to setting/tuning SU's, it may be helpful. Link below
https://www.jaguarforums.com/forum/x...17/#post928571

See mine below.
 

Last edited by o1xjr; 10-09-2014 at 04:36 PM.
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Old 10-09-2014, 04:51 PM
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Good idea, Clarke. Thanks. Hopefully signature details are there. Let me look at the materials you linked to. Cheers.
 
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Old 10-10-2014, 02:58 AM
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As you have Strombergs, the diaphragm is the most likeley culprit.

The fact the piston is more difficult to slide UP than the rear carby, indicates a very dirty carby housing.

My suggestion is to get 2 diaphragms, 2 minor kits (some of these include that diaphragm, so ASK the questions), and give them both a favour and refresh thm both.

SOME, and I repeat, SOME, USA market cars have what is known as a "secondary throttle plate" between the carbies and the actual inlet manifold. This is controlled by a linkage arrangement to synchronise the opening with the carbies. I have never seen one in the flesh, but have read about that plate being a nightmare, and most owners have removed it.
 

Last edited by Grant Francis; 10-10-2014 at 03:57 AM. Reason: Spelling still sucks
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Old 10-16-2014, 09:24 PM
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Torn diaphragm is common on the Stromberg carbs, this will keep the slide down.
 
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Old 10-17-2014, 08:37 PM
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TR250/TR6 Carbs Part I

Above is an outstanding source for Stromberg overhaul and tuning. A real blow-by-blow account with pics Special tool needed to alter the mixture.

Thank you all. Yes, switched the diaphragm and cleaned both carbies. They weren't very dirty at all but, hey presto, once cleaned, all is working nicely.

The plugs previously showed over rich mixture and now nice and clean. Drove the car a lot today so tomorrow will pull the plugs again and check. If sudden change I'll be back here for advice

Thanks so much,

Graham
 
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Old 10-18-2014, 09:14 AM
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Originally Posted by Series1fan View Post
The plugs previously showed over rich mixture and now nice and clean. Drove the car a lot today so tomorrow will pull the plugs again and check. If sudden change I'll be back here for advice

Thanks so much,

Graham
I will be doing around 500km in mine tomorrow just to have a beer with other JF members. If I have trouble I will post again too. Or if I don't have trouble I might come back and post again .........

EDIT actually ,looking at the clock that road trip would be today!
 

Last edited by o1xjr; 10-18-2014 at 09:16 AM.
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Old 10-18-2014, 08:08 PM
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How did the trip go, Clarke: car go a treat?

Pulled the plugs today after more driving and looking really sweet.
 
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Old 10-19-2014, 05:03 AM
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Originally Posted by Series1fan View Post
How did the trip go, Clarke: car go a treat?

Pulled the plugs today after more driving and looking really sweet.
Just got home and posted the pics. link below, page 3, post #50.
https://www.jaguarforums.com/forum/a...-127568/page3/

Car ran sweet, sat on 65-80 mph all the way down and back(it seems to have a real sweet spot at about 75 mph). Passed lots of unsuspecting drivers in my old banger.
412 km, used 62 litres of fuel. Averaged 15L/100km. A far cry from the 21L/100 it was using when I got it.

Good to hear yours is running sweet too.
 
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Old 10-23-2014, 06:59 PM
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Australia no longer uses Imperial?

Hi Clarke, looked over the pics of the trip you took. Nice! Yours the eldest there?

Love that avatar pic of the MK 2 (?) pulling the caravan.

Thanks for these mileage numbers. I'll run mine but they aren't as good as you're getting, I'm pretty sure. Still got one or two issues to resolve and then maybe.
 
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Old 10-24-2014, 06:57 AM
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Originally Posted by Series1fan View Post
1.Australia no longer uses Imperial?

2.Hi Clarke, looked over the pics of the trip you took. Nice! Yours the eldest there?

3.Love that avatar pic of the MK 2 (?) pulling the caravan.

4.Thanks for these mileage numbers. I'll run mine but they aren't as good as you're getting, I'm pretty sure. Still got one or two issues to resolve and then maybe.
Hi Graham,
1. We use km but my car is in mph.

2.Youngest member, oldest car!

3.That was Ken's MkII on a family holiday in the Blue Mountains parked outside his inlaws house I believe.

4.Those carby's have been apart a few times now, I think every part that can be replaced has. I have tried 2 sets of needles as well. Still doe's not idle as smooth as I would like. But will have to live with that,when I have had it idling smooth the fuel burn goe's up to 17-18L/100km.(richer mixture)
Best compromise I guess,until I learn a bit more.
 
 
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