zodiac3813 Posted December 15, 2009 Share Posted December 15, 2009 Hi all..... I have an LSA55 with a reco 2.2 (120hrs). Has anyone had problems with fouled plugs causing mis-firing? I have on a couple of occasion experienced this on the R)mag when doing pre takeoff checks, with the occasional miss on both mags. The first time it happened, I put it down to a faulty spark plug and fitted a new set...... problem fixed, until about 3 hrs flying later: same problem again, with the occasional miss on both mags. This time I blamed Murphy and (reluctantly) changed th plugs again. Fixed for another 3 hrs. THIS time I narrowed the miss down to no. 4 cyl and removed the 2 plugs... the appeared oily, one more so than the other. Put in 2 of the many 2-hour old plugs piling up on the workbench, and presto! Running like a clock. What puzzles me is that the oil consumption isn't excessive (for a Jabiru)... maybe 100 mls in 3 hours, with some blowback. The cylinders & heads have been off, when all the through bolts were replaced at around 90 hrs due to a broken one. Slight glazing of the bores, possibly due to a soft run-in (previous owner!), but otherwise all appeared ok. All work done by a Level 2..... leak-down test at 100 hrs was satisfactory plug leads replaced all plugs gapped at .020, coils at .010 distributor caps checked, rotors tight nil overheating, temps always well in the green I would have thought that a slight oil leakage into the chamber, either past the valves or rings (as cyl. no. 4 appears to have), would be burned off by ignition: so after some advice and consultation, I can only conclude that the spark is too weak, allowing the plug to become fouled over time. Any input would be greatly appreciated, as I need to sort this problem before a Bass Strait crossing next May! Cheers, Jim Link to comment Share on other sites More sharing options...
facthunter Posted December 16, 2009 Share Posted December 16, 2009 Fouled plugs. You don't say whether you are using avgas and what oil . Most oils contain friction modifiers and these can short out plugs as they are metallic salts, when an engine is passing oil to the combustion chamber. Oil can get down the inlet valve guides too. Lead deposits (possible with avgas) are easily recognised and the effect can be moderated by ensuring that the correct heat range is used. Nev Link to comment Share on other sites More sharing options...
Tomo Posted December 16, 2009 Share Posted December 16, 2009 To cause irregular burning on either spark plug in the same pot certainly makes you wonder what I could be... Have you checked you are doing the correct valve clearances? Valve clearances are a very important and must be done correctly, if not... When the engine heats up, things expand and the clearance can get closed up, and if it is to much the valves will start 'ridding' generating less compression due to not closing off sufficiently etc... will eventually burn out the valve. Lower compression, less bang, less heat, will cause oil build up in the plug, slowly shorting them out etc etc... If the spark wasn't as 'juicy' on those plugs/leads, it could do it also, as you already thought, but if you have new leads, and have checked the coil(s), also it'd be pretty hard to imagine both coils playing up on the same cylinder! If you have one, or know someone with one, a thermo temperature gun is awesome for working out these sort of things - run the engine for 5 mins or so and then use this temp gun to check each cylinder exhaust port, generally as a rule they all should be relatively similar to each other... the hotter it is, the leaner - the colder it is, the richer... Glazed bores will cause irregular compression problems... Is it just No 4 playing up? Fuel type shouldn't be a problem if it is only the one cylinder playing up. I don't think it is your electrical system or faulty plugs, I'm fairly convinced it'd be something to do with that cylinder, A leak down test when it is hot would be a good thing if possible. Anyway I hope you find the problem... Ps. This is only my opinion, and you should do as you feel is right or consult an aircraft mechanic... Link to comment Share on other sites More sharing options...
jetjr Posted December 17, 2009 Share Posted December 17, 2009 Other option would be plug leads, or electrical problem Ive had this on automotive engines, a crack in outer sheath used to come good every time it was moved but would resettle onto block and start grounding after a few hours I ran the engine in the dark and spark leakage was very obvious but dont recommend playing with running prop in the dark!!!!! Just have a good look at plug leads and anywhere they are touching metal or show wear. When you pull the plugs are they fouled up? You should be able to test them and see if still sparking Also check coil gaps, if too wide can give weak spark JR Link to comment Share on other sites More sharing options...
zodiac3813 Posted December 18, 2009 Author Share Posted December 18, 2009 Hi again and thanks for the prompt responses..... since writing, I conducted 4 x short flights while fine-tuning the airflow through the cowls (added a lip at rear of bottom cowl), as the oil temp had been getting close to 100 deg C on hot days. The OAT was 29 deg. Not a hint of a misfire on all mag checks and during flights! It's not a consistent problem, that's for sure...but when it happens, the only way to fix it is to change those plugs! For the record..... valve clearances were correctly set 20 hrs ago by mechanic/level 2 fuel used is BP Ultimate 98 octane oil is aeroshell 15W50 after misfiring, the plug electrodes on no. 4 appeared oily (one more so than the other) when Jabiru reco'd the engine, they replaced 1xcoil and left the other original one (??) Thanks again, will keep plugging away (no pun intended!)..... Cheers, Jim :thumb_up: Link to comment Share on other sites More sharing options...
Bruce Tuncks Posted January 5, 2010 Share Posted January 5, 2010 fouled plugs I had a problem of mis-firing when my Jab was new. It happened on the first take-off of the day, some beats missing at about 300 ft. People on the ground noticed it. Well after a LOT of asking around, and some false tries, I found that the plugs had been getting fouled up at the end of the previous flight on the low-throttle settings. The factory said to adjust the carby taper tube to lean off the mid-range by one notch. They ship the engines out to run richer rather than leaner, as richer is safer for the engine. Another Jab owner, who had been a mechanic for racing motorbikes, said the plug was too cool and to go to the next hotter plug, a D8EA. I was also told to give bursts of high throttle after times of low throttle, to clear the plugs. (Instructors do this on engine-failure checks, for this reason and not just to keep the engine warm) Now I should have done one thing at a time, but I did them all at once and the problem has not happened again. cheers, Bruce Link to comment Share on other sites More sharing options...
theoy Posted January 9, 2010 Share Posted January 9, 2010 below info not directly related to fouled s/p but it could be of some use. I have being using NGK Iridium spark plugs now for 300+ hours on avgas. I was told they give a better spark on a Jabiru J160 2.2L weak ignition system. I will try the 400 hour mark before changing or if i get cold feet sooner. I had to re adjust them back to .025. at 200 hours and again at 300 hours. The s/p were used during a short 100 hour period when the carby was set factory rich and glazed bores, using excessive oil piston ring bypass. Last 200 hours carby set on about 16L burn at about 3000 RPM below 5000 feet, 60X44 prop. Ring Wayne Johns to fix your problem. I have his mob. Cheers Link to comment Share on other sites More sharing options...
Steve Donald Posted January 11, 2010 Share Posted January 11, 2010 below info not directly related to fouled s/p but it could be of some use.I have being using NGK Iridium spark plugs now for 300+ hours on avgas. I was told they give a better spark on a Jabiru J160 2.2L weak ignition system. I will try the 400 hour mark before changing or if i get cold feet sooner. I had to re adjust them back to .025. at 200 hours and again at 300 hours. The s/p were used during a short 100 hour period when the carby was set factory rich and glazed bores, using excessive oil piston ring bypass. Last 200 hours carby set on about 16L burn at about 3000 RPM below 5000 feet, 60X44 prop. Ring Wayne Johns to fix your problem. I have his mob. Cheers Hiya Theo, i agree the NGK Iridium spark plugs are the go, did you notice the complete burn you get especially when you mag check no noticeable rpm drop a complete burn still occurs on 1 plug due to the spark pattern being full circle omnidirectional, std plugs fire a figure eight shape spark, then you have resistance factors Iridium plugs only have one third the resistance of a standard plug , much less work on the ignition system, here is a test you can try for yourselves fit a half shot coil and crook spark lead with std plugs it will miss and break down change plugs to Iridium you will find in most cases it will run quite well, you will also notice cold starts are better as is throttle response, i would not run any other plug better overall performance with less load on the whole ignition system, resistance = heat and heat is the killer of coils and most components. only bugger is they cost $20 each still it is better than being in the air wishing they were fitted , cheap added safety, cheers Steve:thumb_up: Link to comment Share on other sites More sharing options...
pudestcon Posted January 11, 2010 Share Posted January 11, 2010 NGK Iridium spark plugs - you got a part number or name apart from Iridium? Pud Link to comment Share on other sites More sharing options...
Vev Posted January 11, 2010 Share Posted January 11, 2010 Hi Pud, I put the Iridium NGK XI9EAR in my Jab and have had them in there 125 hrs ... had a look at them on the weekend when I did my 25hr oil change and they still look perfect. The guys at Jab but me onto them and said they use them in their own aircraft. Cheers Jack Link to comment Share on other sites More sharing options...
dazza 38 Posted January 11, 2010 Share Posted January 11, 2010 Hi guys, i used a iridium plug in my yamaha wr426 enduro bike when i had it, i had the same problem before, ie- fouled plug , it was quite common(due to the pumper carby design, but thats another story). The iridium plug solved the problem. Back to topic- with iridium plugs , even though they last for a realy long time, just a word of caution, the electrodes only about 0.4mm thick so have a realy good look them when inspecting them. They can become brittle from time to time and break off.Cheers Link to comment Share on other sites More sharing options...
slartibartfast Posted January 11, 2010 Share Posted January 11, 2010 Thanks for the part number Jack, but I couldn't find it. The NGK website says the Iridium version of D9EA is DR9EIX. Can anyone confirm this is the one they are using? I want to try them out. Link to comment Share on other sites More sharing options...
Derby Posted January 12, 2010 Share Posted January 12, 2010 Hi, Slarty yes thats the one D9EIX i have used them for about 250 hours now,i would not go back to D9EA's now.You can get them on special at super cheap every now and again for about $15. Rory Link to comment Share on other sites More sharing options...
slartibartfast Posted January 12, 2010 Share Posted January 12, 2010 Cheers Rory. Link to comment Share on other sites More sharing options...
Vev Posted January 12, 2010 Share Posted January 12, 2010 yes .. sorry guys I had stuffed up that part number ... it is in fact DR9EIX. By the way, on the weekend I took a look at my HT plug leads and noticed some rubbing between the leads where they cross over between the distributors. I was wondering, if this was left unchecked could this be the source of shorting between the leads and be a cause for plug fouling? Could it also explain why one would still experiance a missfire on both mags? Just a thought? Cheers Jack Link to comment Share on other sites More sharing options...
slartibartfast Posted January 12, 2010 Share Posted January 12, 2010 Cool. Just bought 8 of them delivered from the UK for $102. This eBay store. 1 Link to comment Share on other sites More sharing options...
zodiac3813 Posted January 12, 2010 Author Share Posted January 12, 2010 Thanks heaps for all the info, I just ordered iridium plugs from the store suggested, having trialled 2X of them on the pot that appeared to be missing.... can anyone suggest the safest way to adjust the gap? They say not to change them at all, but obviously they're way to wide at around .028" or whatever? Also thanks Maresi, I would like to have Wayne Johns contact details: you can send them to my email address if need be, it's [email protected] Cheers, Jim Link to comment Share on other sites More sharing options...
jetjr Posted January 13, 2010 Share Posted January 13, 2010 By the way, on the weekend I took a look at my HT plug leads and noticed some rubbing between the leads where they cross over between the distributors. I was wondering, if this was left unchecked could this be the source of shorting between the leads and be a cause for plug fouling? Could it also explain why one would still experiance a missfire on both mags? It would have to be bad but yes, the insulation can crack too and let spark out, can even be intermittant with vibration etc Link to comment Share on other sites More sharing options...
jetjr Posted January 13, 2010 Share Posted January 13, 2010 Ive found a source in US that can land 8 x DR9EIX here for approx $83 AUD Anyone else interested? PM me as it may save some freight cost Link to comment Share on other sites More sharing options...
dazza 38 Posted January 15, 2010 Share Posted January 15, 2010 Thanks heaps for all the info, I just ordered iridium plugs from the store suggested, having trialled 2X of them on the pot that appeared to be missing.... can anyone suggest the safest way to adjust the gap? They say not to change them at all, but obviously they're way to wide at around .028" or whatever?Also thanks Maresi, I would like to have Wayne Johns contact details: you can send them to my email address if need be, it's [email protected] Cheers, Jim HI JIM im no expert, but i didnt change the gap, although they were wider than the normal plugs. They need a wide gap to work properly.Cheer :big_grin: Link to comment Share on other sites More sharing options...
Captain Posted January 28, 2010 Share Posted January 28, 2010 I don"t know what you are all worried about. Once you do the research to see how Spark Plugs are made, you'll never be concerned again. See below, so you can all relax .................. Hope you find this helpful Regards Geoff [ATTACH]9788.vB[/ATTACH] [ATTACH]9789.vB[/ATTACH] [ATTACH]9790.vB[/ATTACH] [ATTACH]9791.vB[/ATTACH] [ATTACH]9792.vB[/ATTACH] [ATTACH]9793.vB[/ATTACH] [ATTACH]9794.vB[/ATTACH] [ATTACH]9795.vB[/ATTACH] [ATTACH]9796.vB[/ATTACH] [ATTACH]9797.vB[/ATTACH] Link to comment Share on other sites More sharing options...
Tomo Posted January 29, 2010 Share Posted January 29, 2010 ... :ah_oh: ... A fair bit of swarf about...!:rolleyes1: Link to comment Share on other sites More sharing options...
Yenn Posted January 29, 2010 Share Posted January 29, 2010 You missed the one where they drive the insulator into the sleeve with a 4lb hammer, that used to be done by the girl with the big bandage on her thumb. Link to comment Share on other sites More sharing options...
Guest Des Funslow Posted January 30, 2010 Share Posted January 30, 2010 A picture is worth a thousand words' I wonder what brand they end up as. Link to comment Share on other sites More sharing options...
phvdw Posted February 5, 2010 Share Posted February 5, 2010 hi, are you shure about the the number as I can't find them on the site from NGK Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now