I've just bought a set of 10mm HT leads for the 16v as the old ones were leaking current (as I found out ) and not the best of quality.
So, without rushing I swapped each lead in turn for it's replacement - checked everything was connected and... it wouldn't catch. So fiddled a bit more with the connections and it fired up. Then - at idle - it stalled. So tried again but failed to get it to run. So, worried I might have fried the distributor or something else, replaced them with the old set - and whaddya know? I fired up fine.
I am confused. I don't think these leads are defective - I would have thought if one was not working I'd get a misfire... Am I missing something???
Is there not enough oomph in the battery? Any advice? (I was going to change the distributpr cap and rotor too, but I've decided to leave it all for the time being!).
If there's enough power in the battery to crank the engine, then there's plenty to run the ignition. After all, you can get a petrol engine running on a 9v battery.
now that explains that then! My alternator failed last week, found it very strange that the car had been running perfectly over a 40 minute drive, then after being switched off for 10 minutes would not start and only seemed to have 11v or so accorss the terminals. Another mystery solved.
Well, seeing as it ran OK for about 30 seconds before stalling I think I had them the right way round. The plugs are brand new NGK three prongy ones... And have been fine.
I will check next week (I'm off in the ZX for a long weekend), but I will fit the new dizzy cap etc. then too. And make sure I have ALL the connections right.
I guess so long as it runs on the old leads for the time being (until the next damp spell lol!) there's no rush to get it right.
I'll have a read of the info I got with the leads, but it does say 10mm somewhere!
It's a bit of a long shot, but are you sure the leads are pushed on to the cap fully? I have come across situations where the rubber boot is such a good air seal that there is a pressure build up within the boot - so after a period of time it pushes the boot slightly away and breaks the contact...
Rectified by just lifting the edge of the boot slightly to relieve pressure.
It could be a faulty king lead though - I had the same problem on a Rover V8 engine and the only thing I didn't rule out was the 3 month old set of genuine Land Rover HT leads! (Not helped by the fact that there was a spark with the plugs out of the cylinders, but NOT under compression).
It might be useful to swap them over again and if the problem persists, have a look at it at night - when you can see any HT leakage.
Those Bougicord style rubber blocks have to be the greatest source of engine misses known to man.
A lot of engine rough running is more often than not cured accidentally by people fiddling with these leads and suddenly it mysteriously starts to behave.
What happens is that the extended rubber end that connects to the plug is longer than normal beyond the actual terminal, as a result it starts to taper back in as it gets to the end. Being dry rubber, it grabs and flexes and holds the metal part on the lead back from the top conductive terminal on the plug. Whilst all this is happening, the big rubber block at the bend where it goes down to the valley, is also binding on the head and sometimes the adjoining lead also and a similar situation often happens at the distributor end.
I've made it a practice over the years to spray the inside of each lead where it pushes onto the plug, with silicone release spray as well as the big nobbly bit at the elbow. I find that once you do this, these leads slip down quite easily and you can feel and sometimes hear a distinct click as the lead firmly attaches to the top of the spark plug. I also usually spray the rubber at the distributor end and sometimes the plastic too, so that that is also a solid fit. This way, there's little chance that the plugs will not be in direct contact with the leads, thereby eliminating the chance of the last couple of millemetres being powered by spark induction as the plug attracts the spark rather than being fed as a constant link to the lead.
I've often wondered about all the distributor cap failures that you guys seem to get over there as to whether intensification of spar due to non direct contact between the terminals at either end could explain why you guys seem to go through dissy caps hand over fist, yet we rarely ever hear about it over here.
Alan S
By the time you're old enough to know it all, you can't remember why you were learning.
Philip chidlow wrote:Would it be OK to keep the original king lead and then see?
I think I know the answer to this already... but could I swap one lead at a time to see if one is defective?
(thought not )
Yes, you can do this, as you already know that you have a working (in the dry) set so you can eliminate each lead at a time. I would check the king lead first (if you are certain that they are on fully) as it does sound like a problem affecting all plugs, not just one, as that would lead to a rough running engine and not cause it to cut out.
) and not the best of quality.
)