Jaguar XK140 Coughing

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Discussion

jjbradders

Original Poster:

80 posts

100 months

Monday 25th April 2016
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Well there's no vacuum at all just for the time being as I'm swapping distributors, so that's probably why. My Fiat doesn't have a vacuum advance though, so I'm not sure what the benefit is? IIRC it's about engine load?

Talking about vacuum, what are the typical symptoms of a vacuum leak? I only ask because I'm not 100% sure of the manifold to head seal.

That's a great diagram thanks, I'll have a look when I run it tomorrow.

Thanks for all the help again

James

a8hex

5,829 posts

222 months

Tuesday 26th April 2016
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The vacuum advance is kind of optional. The racing Jag engines don't bother with it since there you want maximum poke all the time whereas on a road engine most of the time you're pootling around and some vague concept of economy can be useful. Basically it just adjusts the ignition timing depending on the engine load and therefore the vacuum in the inlet manifold allowing it to be timed more aggressively when needed and more gently when the engine isn't having to try too hard.

jjbradders said:
I'm going to fit one of these 123 electronic ignition distributors instead but I'm waiting on that.

Has anyone actually driven an XK, and what are the things to watch out for?

Cheers

James
I didn't get your question about driving XKs
I've never driven one on Webers only on SUs which are by all accounts simpler to setup, but even then it can take long enough. But the advise I was always given was make sure you've got the ignition setup right first.

I know a lot of people have got on well with the 123, but when the current engine was installed in my XK150 we couldn't get the 123 to work well with it, none of the curves it offered would agree with my engine so in the end we went back to a normal one. Since then they've brought out the version you can program yourself. CKL kept being promised a test one to try out with my engine, but it never showed up. But that was a number of years back.

My recent rough running problems have been down to ignition issues, most recently dodgy ancient leads.

Running the engine in the dark is the best way to look at that type of issue. I still can't find any cracks in my old distributor cap, but run it in the dark and you can see straight through it and see what'd going on inside. Very pretty but not very useful.

jith

2,752 posts

214 months

Tuesday 26th April 2016
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a8hex said:
My recent rough running problems have been down to ignition issues, most recently dodgy ancient leads.

Running the engine in the dark is the best way to look at that type of issue. I still can't find any cracks in my old distributor cap, but run it in the dark and you can see straight through it and see what'd going on inside. Very pretty but not very useful.
Another way of testing them I found was to get the wife to hold the plug cap onto her tongue to see if the spark jumped.

It worked and I got peace for a week. evil

J

TonyRPH

12,963 posts

167 months

Tuesday 26th April 2016
quotequote all
lol.

Slightly off topic - my former sister in law could pull plugs leads off a running engine without feeling a thing.

I couldn't even touch them when they were still attached to the plug, without getting a hefty belt.

I don't know how she didn't get a shock.

jith

2,752 posts

214 months

Tuesday 26th April 2016
quotequote all
TonyRPH said:
lol.

Slightly off topic - my former sister in law could pull plugs leads off a running engine without feeling a thing.

I couldn't even touch them when they were still attached to the plug, without getting a hefty belt.

I don't know how she didn't get a shock.
Did she work on the buses as a conductor? getmecoat

J

TonyRPH

12,963 posts

167 months

Tuesday 26th April 2016
quotequote all
jith said:
Did she work on the buses as a conductor? getmecoat

J
Ahem..

Would sir like his coat now?


jjbradders

Original Poster:

80 posts

100 months

Saturday 30th April 2016
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Well she's running a charm now! (The car that is...)

The mains are a little lean so I'll get the next size up. But thanks for all the input so far!

So now the electrical faults have started: The petrol gauge won't turn off with the ignition switch and it keeps flicking between full and empty. The ignition switch also occasionally doesn't cut power to the car after the engine has been running for a bit. Do these sounds like grounding issues?

Thanks again


uk66fastback

16,455 posts

270 months

Monday 2nd May 2016
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Yes, earthing problems usually ... you'll have to get the wotsit out and go through it all ...

jjbradders

Original Poster:

80 posts

100 months

Wednesday 4th May 2016
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uk66fastback said:
Yes, earthing problems usually ... you'll have to get the wotsit out and go through it all ...
Ah yes, the good ol' Wotsit...

Vanin

1,010 posts

165 months

Thursday 5th May 2016
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TonyRPH said:
lol.

Slightly off topic - my former sister in law could pull plugs leads off a running engine without feeling a thing.

I couldn't even touch them when they were still attached to the plug, without getting a hefty belt.

I don't know how she didn't get a shock.
Was she a bright spark with an earthy sense of humour?


Going back to the OPs problems, I have had no end of issues with poor fuel quality. Make sure that you siphon the tank if it has been sitting there a while and fill with good quality ( non supermarket) and maybe with an additive to rule that out of the equation

Perseverant

439 posts

110 months

Sunday 8th May 2016
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Nice to read anything XK related. My XK120 roadster remains a pig when it's cold. It has 2 inch SU carburettors and an eccentric cold start device rigged up by a former owner - basically a wire loop which lowers the jet on the rear carb. only and thus aids starting. The original needles were the richest available which worked as long as the throttle was wide open - the tale was that a previous owner had tried sprints and hillclimbs. I went down a couple of sizes and it's generally much better. Good luck anyway from NE Scotland.

Vanin

1,010 posts

165 months

Sunday 8th May 2016
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Perseverant said:
Nice to read anything XK related. My XK120 roadster remains a pig when it's cold. It has 2 inch SU carburettors and an eccentric cold start device rigged up by a former owner - basically a wire loop which lowers the jet on the rear carb. only and thus aids starting. The original needles were the richest available which worked as long as the throttle was wide open - the tale was that a previous owner had tried sprints and hillclimbs. I went down a couple of sizes and it's generally much better. Good luck anyway from NE Scotland.
My 120 Roaster 1952 is similar to yours from cold. It fires once then kicks out the starter. It has electronic ignition which improved things but when it is being a particular pain, I have found that leaving it for thirty seconds between crankings somehow works better than continuous cranking.
This may be due to better vapourisation or perhaps some other reason but I would say fuel related rather than electrical.
I have the same simple solenoid "choke" and would be interested to hear of any easy fix improvement in that area.

jjbradders

Original Poster:

80 posts

100 months

Sunday 8th May 2016
quotequote all
Well I'll try the flush idea. Also going to fit larger mains and pump jets too, just because it feels like it's leaning out.

Finally took a few decent pictures after giving it a wash and brush up.



Sadly the Jag isn't here anymore due to the joys of A levels, so I'm getting it back in July to work on. In the mean time, I have a Fiat X1/9 to spray, so that'll keep me busy

jjbradders

Original Poster:

80 posts

100 months

Sunday 8th May 2016
quotequote all