spark plug gap closed on two plugs, what causes this? |
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spark plug gap closed on two plugs, what causes this? |
siverson |
Jun 13 2016, 09:23 PM
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#1
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Advanced Member Group: Benefactors Posts: 2,451 Joined: 5-May 03 From: San Diego, CA Member No.: 654 Region Association: Southern California |
hi - quick question from the garage. cdi box died on my six. got replacement and car starts right up (good). but runs like crapola right away. pulled the plugs and on two the electrode (term?) is no touching the plug.
is this why my cdi boxed died? or is this a result of it dying? or? plugs were 1k miles old. cdi box was 46 years old. |
veekry9 |
Jun 13 2016, 10:34 PM
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#2
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OldMember Group: Retired Members Posts: 3,068 Joined: 17-June 13 From: TO Member No.: 16,025 Region Association: Canada |
(Pelican Pix)
They can look as bad as this before they leave the engine. https://www.google.ca/search?q=porsche+911+...rP5n8IZN9mSM%3A What you typed: "...pulled the plugs and on two the electrode (term?) is no touching the plug." What you meant: "...pulled the plugs and on two,the cathodes are now touching the electrodes."(meaning,the gaps are closed) The closed gap will indeed ruin the output transistors of the cdi amplifier. Carbon buildup on the pistons are usually the culprits,running way rich and or lousy valve guides or poor ring sealing. A short term fix is a shim for the plugs,to recess them up,away from the pistons. For sure use copper formula antiseize on the plug threads. https://www.google.ca/search?q=copper+anti+...RjOD2EQ_AUIBigB A look inside to check the condition of the cylinders,with your recording borescope,will give a good reading of the overall condition. https://www.google.ca/search?q=recording+cc...1JWDlQrLkBnM%3A Roll the engine over to look at each valve in turn,(12),inspecting the seats and valve head.A comprehensive leakdown test is next. A black,wet looking carbon deposit on pistons,chamber and valves means it's time for some headwork,at minimum. A single plug six is sensitive,and must be maintained,otherwise..(Kaboom!). BTW,a solid state ignition makes a hotter spark,the signal edges much sharper than what mechanical points can produce. http://www.123ignition.nl/brand/porsche.html There,spent some of your money in a most cost effective way,avoiding the inevitable explosion,and rod through block tears. (IMG:style_emoticons/default/biggrin.gif) / https://www.google.ca/search?q=spark+plug+s...8dHcfDRqr2aM%3A Bill Jenkins found hp by indexing the plugs in his prostock 'sbc'engines,so too should the gap be pointed into the center of the cylinder of the 911 'hemi' engine. / |
nine9three |
Jun 14 2016, 10:12 AM
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#3
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Member Group: Members Posts: 142 Joined: 29-December 11 From: Oregon Member No.: 13,946 Region Association: Pacific Northwest |
Carbon buildup on the pistons are usually the culprits,running way rich and or lousy valve guides or poor ring sealing. A short term fix is a shim for the plugs,to recess them up,away from the pistons. For sure use copper formula antiseize on the plug threads. After reviewing the photos again, I believe this is your problem. The fact that some are touching and others are not leads me to this result. The plugs are certainly carbon fouled. I also agree that shimming the plugs would be a temporary fix. Getting to the source of the over rich situation is the real issue. Fuel, valve adjustment, timing etc. Good Luck! |
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