tonymitsiv6 Posted March 23, 2017 Report Share Posted March 23, 2017 Hi, new on here. Anyone know about short circuit coilpacks and consequent missfire? I have replaced 3 so far and all show signs of electrical burn through on the rubber tube going down to the spark plug. OK I am using second hand replacements as new ones are so expensive. I can use just the tube but these are difficult to find. Link to comment Share on other sites More sharing options...
treks Posted March 24, 2017 Report Share Posted March 24, 2017 Are you using the specified spark plugs, and/or are the plugs gapped correctly? Link to comment Share on other sites More sharing options...
tonymitsiv6 Posted March 24, 2017 Author Report Share Posted March 24, 2017 yes, using plugs as detailed in handbook. Problem arose before fitting new plugs and seems to occur on the plastic tube that goes from the coil to the plug top. It shorts between the tube and the head. The tube is about 10cms long. Link to comment Share on other sites More sharing options...
treks Posted March 25, 2017 Report Share Posted March 25, 2017 (edited) OK, so if the plugs are good, the most likely possibilities are either that the plug leads and suppressors are just old, or that the leads and suppressors are not OEM grade. Plug leads and suppressors do break down after a few years due to the constant heat they are exposed to, but replacing them with old, used leads that are likely just as old won't fix the problem. Best thing to do here is to replace the leads and suppressors with OEM parts. Edited March 25, 2017 by treks Link to comment Share on other sites More sharing options...
tonymitsiv6 Posted March 25, 2017 Author Report Share Posted March 25, 2017 sure thing, but with a V6 and $140 a pop, it's tempting to get used ones. What I can't work out is how the H.T current burns through the quite thick plastic material - always in the same place. Link to comment Share on other sites More sharing options...
treks Posted March 25, 2017 Report Share Posted March 25, 2017 Over time the insulating material develops small cracks and weaknesses that are not visible to the naked eye. So, considering that electricity is much like water in that it will always follow the path of least resistance, it becomes easy to see how several tens of thousands of volts will jump through a break in the insulation to the point that is closest to a grounding point- which in this case, is the point on the cylinder head that is closest to a weak spot in the insulating material. Link to comment Share on other sites More sharing options...
Gaurav Posted March 25, 2017 Report Share Posted March 25, 2017 Is your coilpacks are working fine...? Is your HT leads connecting in proper order on each bank? Is this shorting happening on all tubes or just one or two? I assume 6G72 means 3.0 Pajero, do you mind sharing some background history as to how and when you spotted this? Let's root for each other & watch each other grow. Link to comment Share on other sites More sharing options...
Gaurav Posted March 25, 2017 Report Share Posted March 25, 2017 To some extent, I agree with treks as Mitsubishi coil and spark related department is extremely sensitive. I vaguely remember long ago something happen with my 6G74 and tried coil pack from scrap and it did't work out as expected. Eventually I have to buy 3 new coil pack as Mitsu support 2 HT lead per coil, so you don't need six. Let's root for each other & watch each other grow. Link to comment Share on other sites More sharing options...
tonymitsiv6 Posted March 25, 2017 Author Report Share Posted March 25, 2017 the 6G72 is fitted to quite a number of cars in USA and Japan. We buy mostly used imports from Japan (I am in New Zealand). My car is a 99 Chariot Grandis Royal 7 seater. The fault showed up as a miss fire with usual hesitant running. It would be easy to mistake it for unbalanced wheels or bad plugs. I was not looking forward to removing the rear plugs as when I looked online it seemed to be an involved process. Luckily on the Grandis there is a bit of space at the back of the engine. You need a long plug socket to reach down in the head and you don't want to get it stuck down the hole! As I had a set of plugs (NGK) I set about changing them. It was then I noticed the burn through on the tube. It was easy to not notice this fault as the burn through mark was only small. I have replaced 3 so far so am getting good at it! Link to comment Share on other sites More sharing options...
Barry Posted March 26, 2017 Report Share Posted March 26, 2017 I saw this on a 6G72 a couple of weeks ago. The spark was jumping down down the insulator and had etched a black track down it. I wanted to show you a pic but I've thrown the plugs. Link to comment Share on other sites More sharing options...
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