{"id":1192,"date":"2013-03-06T17:55:00","date_gmt":"2013-03-06T22:55:00","guid":{"rendered":"https:\/\/cubcadetman.com\/cc\/?p=1192"},"modified":"2014-03-09T20:22:17","modified_gmt":"2014-03-10T00:22:17","slug":"no-spark","status":"publish","type":"post","link":"https:\/\/cubcadetman.com\/cc\/uncategorized\/2013\/03\/no-spark\/","title":{"rendered":"No Spark"},"content":{"rendered":"

Let\u2019s attack what I consider the easiest problem to solve first; an electrical one with no spark.\u00a0 The operation of a single cylinder engine is pretty simple.\u00a0 As the piston travels downward, it sucks air and gas from the carburetor into the cylinder.\u00a0 As the piston travels upward, it compresses the air gas mixture.\u00a0 The spark plug ignites the mixture causing an explosion that forces the piston back downward.\u00a0 (I know. I know. It requires valves opening and closing and proper timing, but I\u2019m trying to keep this explanation as simple as possible.\u00a0 I\u2019ll write an article later on more advanced stuff \u2013 like timing.)<\/p>\n

The first thing I do if I have an electrical problem is to check at the spark plug.\u00a0 I\u2019ve tried using those \u201cspark plug checkers\u201d, but I\u2019ve had the best luck by removing the spark plug.\u00a0 After the spark plug is removed, ground it against the block and crank over the engine. Again, be careful.\u00a0 We\u2019re dealing with a high voltage.\u00a0 It won\u2019t kill you but it will sure hurt like the dickens.\u00a0 I lay the spark plug on the engine; I don\u2019t even hold it by the spark plug wire.\u00a0 What you check next depends upon what you observe:<\/p>\n

This is what I always hope for with an electrical problem.\u00a0 It\u2019s the easiest to debug.\u00a0 If I don\u2019t have a spark, the first thing I try is a new spark plug.\u00a0 If that doesn\u2019t cure the problem (usually doesn\u2019t) it\u2019s going to require the use of a voltmeter. (There will be a discussion on voltmeters in another article (when I get time) if you don\u2019t own one or have never used one.)\u00a0 Set your voltmeter to read DC volts.\u00a0 With the key off, connect the positive lead of the voltmeter to the + (positive) terminal of the coil and connect the negative lead to a good ground.\u00a0 (A pair of jumper wires is a big help in any electrical debugging.)<\/p>\n

\"No<\/a><\/p>\n

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When you turn the key on, you should have +12 volts reading on the meter.\u00a0 If you don\u2019t have +12 volts here, you could have a variety of problems that could be as simple as not pushing down the clutch to engage the safety switch\u2014you\u2019re not getting 12 volts from the battery to the coil.\u00a0 (I have eliminated the safety switch on all my Cub Cadets.)\u00a0 Again, this problem is discussed in another article.<\/p>\n

For now, let\u2019s assume you have the +12 volts on the plus side of the coil.\u00a0 Move the positive lead to the \u2013 (minus) side of the coil.\u00a0 With the key on, rotate the engine over slowly by hand.\u00a0 (If you still have the spark plug removed, the engine should rotate relatively easy.)\u00a0 When the points are open, you should have a +12 volt reading on the voltmeter.\u00a0 When the points close, the reading should drop to zero.\u00a0 Briefly what happens is this:\u00a0 With the points closed, the coil is grounded and current flows through the coil creating a magnetic field.\u00a0 When the points open the current stops flowing causing the magnetic field set up in the primary side of the coil to collapse creating a large voltage in the secondary windings.\u00a0 This large voltage causes an arc to jump across the end of the spark plug which ignites the fuel.<\/p>\n

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On the majority of starting problems I\u2019ve worked on, this reading remains at +12 volts. That means the points aren\u2019t grounding the negative side of the coil.\u00a0 This could be a result of the points not completely closely, but generally it\u2019s a result of poor conductivity across the points.<\/p>\n

\"No<\/a>\"No<\/a><\/p>\n

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The picture on the left shows the location of the points with the point cover removed.\u00a0 The picture on the right shows a closeup of the points with the points open.\u00a0 (This point gap is too wide, but illustrates the point.)\u00a0 With the points open, place a piece of paper (notebook paper or a dollar bill works best) in the gap and rotate the engine until the points close.\u00a0 Pull the paper out and repeat the process several times.\u00a0 Sometimes you can see the carbon film thats removed on the paper.\u00a0 This process is especially important when you install a new set of points.<\/p>\n

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Don\u2019t file the points.\u00a0 Just drag a piece of paper through the closed points until you get continuity; i.e., the voltage drops to zero when the points are closed.\u00a0 When the points are operating properly you should be able to use your finger to flip the points open and create a spark at the spark plug (with the key on).\u00a0 (It\u2019s only 12 volts across the points so you won\u2019t get shocked.)<\/p>\n

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 <\/p>\n","protected":false},"excerpt":{"rendered":"

Let\u2019s attack what I consider the easiest problem to solve first; an electrical one with no spark.\u00a0 The operation of a single cylinder engine is pretty simple.\u00a0 As the piston travels downward, it sucks air and gas from the carburetor into the cylinder.\u00a0 As the piston travels upward, it compresses the air gas mixture.\u00a0 The […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[32,1],"tags":[],"class_list":["post-1192","post","type-post","status-publish","format-standard","hentry","category-engine-cranks","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4lT6g-je","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/posts\/1192","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/comments?post=1192"}],"version-history":[{"count":3,"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/posts\/1192\/revisions"}],"predecessor-version":[{"id":1198,"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/posts\/1192\/revisions\/1198"}],"wp:attachment":[{"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/media?parent=1192"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/categories?post=1192"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cubcadetman.com\/cc\/wp-json\/wp\/v2\/tags?post=1192"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}