XK 120 ignition coil
 

Hi There,
I'm trouble shooting an ignition problem with my 1952 xk120. I've had the Carbs balanced, timing is perfect,so I think the main thing left is the coil or condenser (not taking the revs when engine's hot,runs beautifully otherwise) Does anyone know a modern coil and condenser suitable for this engine? I'm based in the south of Ireland and will order the correct items from Guy broad,but would like to take her out this weekend.
Regards,
Scott

Scott welcome to the forum. You must please post up some pics of this car. Why not head into the New Member area and introduce yourself to the guys.

In the meantime I'm moving this to the XK120 section, we have more than a few classic car enthusiasts.

(PS, have you tried SC Jaguar?)

Hi Scott,
Welcome to the site.

I have no firsthand knowledge of XK120s, but that era coils and condensers are relatively "standard" parts.

Just for yocks I punched your car info into a local/ national auto parts site (O'Reillys), and they had the goods.

You should be able to do the same in at any parts outlet in Ireland.

Good luck and happy motoring!:icon_wink:
Retro

You might also look intq an aftermarket (jag ones are too expensive) pointless ignition for any of a number of inline 6 cylinder motors. In th usa they are called hei (high energy ignition) and are not really too expensive. Good luck.

Grrrrrr!
 

Thanks for your replies.
I've put a new coil and condenser in and the problem still persists!! Very annoying, points new, coil new, condenser new, gap good, timing perfect what am I missing out on???? She'll run cleanly then slowly start miss firing after a couple of miles, then come to a complete stop. If I put a cold coil in she'll start then it'll happen all over again!!!!

Did you change the distributor cap, hairline cracks can do funny things when it becomes hot?

Also have a good look at the leads and connections to the coil LT + HT.

Misfires can be a pig to chase down if something is not obviously broken. Yours seems to develop with heat, so could it be a crack, or failing insulator along the line?

In my limited experience you have to start at the beginning and work forward.

Misfire chasing for me falls into 3 categories, Electrical, Fuel, Mechanical (or a mix of the 3 if you are really unlucky).

You seem to have changed some of the obvious items, but plugs and leads? Is your fuel delivery good, a partially blocked F/Filter can cause a problem.

Check, Batt condition and connections, Alternator condition and connections.....

Hope that you get things sorted, just be methodical.

Others will have better advice.

I wouldn't think it would misfire that quickly unless you're running very hot, but the coil location on the 120 is not optimal. Some owners have moved the coil mount off the valve cover to the side of the engine compartment. You might try temporarily doing that - if the problem disappears, at least you'll know it's the coil.

Maybe you have a vacuum in the fuel tank due to a blocked breather. This builds up until the pump cannot draw the fuel.

Thanks.
 

Thanks for your help. I managed to find the problem. The knurled nut on the manual advance and retard had backed off the vacuum assembly this made the points loose so they'd flop around after getting hot!! I have tightened it up re timed her and have done 100 amazing miles!!

coil xk120
 

it is always the last thing you check !!!
interesting and unusual issue you had, and found.
The Lucas coil for the xk120 is easily found at any of the major jag parts suppliers, with a good option for the Lucas Sports Coil..still a spec for the xk120. It does no good, in fact issues arise, to go with any hotter coil. Coils are matched to distrib and plugs..change one much..you must change them all. Once set up as you have found the XK120 runs just fine on the kind of equipment is was manufactured with originally. I would rather work on a stock distrib and contacts and know what is up, than be lost in a new hot rod ignition system. Stay stock..keep driving !!
Nick