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felipe heuser
Experienced User
Username: felipe

Post Number: 95
Registered: 07-2017
Posted on Monday, 30 March, 2020 - 00:28:   Edit PostDelete PostView Post/Check IP

Hello…not sure if I may post here regarding my SCIII where since a year is sporadically running on 7 cylinders…narrowed down to the A4, so exchange spark plug each time and runs normal for a few months however has happened now about four times…

(BTW don't drive it very often)

Felipe - have moved this post to the Silver Cloud and Bentley S section where it is more likely to get a response. David
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David Hughes
Experienced User
Username: wedcar

Post Number: 108
Registered: 07-2004
Posted on Monday, 30 March, 2020 - 13:13:   Edit PostDelete PostView Post/Check IP

Felipe
Issue could well be related to a faulty lead or connection, mark the leads, remove the distributor cap and check condition of the cap internal contacts and clean them, check also for "tracking" or cracks in the cap. Check resistance of leads, from inside cap to plug connection, if "resistance leads" they should be approximately 1000 ohms per foot (300mm), if copper core leads the resistance should be no more than 1 ohm.
Trust that helps.
Regards
David
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Martin Taylor
Experienced User
Username: martin_taylor

Post Number: 179
Registered: 07-2013
Posted on Monday, 30 March, 2020 - 17:51:   Edit PostDelete PostView Post/Check IP

Is the plug oiling up? Does cleaning the plug make it work again?
I would install a hotter platinum or iridium plug in that cylinder if so, or simply do all of them, if it works fine after changing the plug it can’t be much else other than plug failure or oiling.
Is the car getting a good run when you use it?
Check the mixture also as plugs will soot up if too rich
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Robert J. Sprauer
Frequent User
Username: wraithman

Post Number: 601
Registered: 11-2017
Posted on Monday, 30 March, 2020 - 22:34:   Edit PostDelete PostView Post/Check IP

Replace the cap, visual inspection is not always reliable, check the leads under complete darkness for arcing. If you pull the lead on the mentioned cylinder, I'm sure you will see grey spots. Those are the arc witness marks.
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Christopher Carnley
Unregistered guest
Posted From: 109.156.245.194
Posted on Monday, 30 March, 2020 - 19:59:   Edit PostDelete PostView Post/Check IP

Could the string and wax valve seals have failed?

There was an improved silicone rubber version available at service from December 1966.

(Message approved by david_gore)
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felipe heuser
Experienced User
Username: felipe

Post Number: 97
Registered: 07-2017
Posted on Monday, 06 April, 2020 - 05:08:   Edit PostDelete PostView Post/Check IP

Thank you for all suggestions, however will need to look up meaning on some...

My mechanic believes the plug is not sparking due to oil…next time will try cleaning plug rather than changing with new...

Have changed all plugs and when out has a good run…

Recently and before plug problem, all leads and cap changed plus points and condenser for complete tune-up…running smoothly...
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Hubert Kelly
Frequent User
Username: h_kelly

Post Number: 383
Registered: 03-2012
Posted on Monday, 06 April, 2020 - 05:21:   Edit PostDelete PostView Post/Check IP

Hi, have ya checked the dash Potts on the carburettor, if full of carbon piston can stick, lead to rough idle and oiled plugs. Worth a check.. easy to clean

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