Pete D 83 #1 Posted July 5, 2023 (edited) Coil? My tractor starts fine cold but after about 15 minutes it will die when I throttle up, then not restart until it sits for about 10 minutes. Thanks in advance! Edited July 5, 2023 by Pete D Share this post Link to post Share on other sites
ri702bill 8,327 #2 Posted July 5, 2023 Pete - do you hav an inline spark checker?? Use one and wait for it to die. Then see what the checker says... No light means no spark. If if lights, is it erratic?? I was given a 7HP K161-S Yank Start. It was a basket case, but complete. i reassembled it, only to find it had a coil that you could set your watch by when it would die.After a cold start, it ran for exactly 3 minutes. Check it then - no one home..... Put in a new coil - good to go...... If it has spark - it is probably a fuel delivery issue. Could be a plugged gas cap vent or a series of microcracks in the fuel line. Those allow air to weep in and that kills the fuel supply. Funny, there is no external dripping of fuel visable... letting it sit allows the fuel to dribble back in... 1 Share this post Link to post Share on other sites
Pete D 83 #3 Posted July 5, 2023 (edited) Thanks, @ri702bill. I need to buy an inline spark tester. I think I will do so right now. (EDIT: Arrives on Friday) I replaced all of the fuel line a month or so ago, but it seems not to fill the fuel filter well. Is there a fuel pump, or is this, as I suspect, gravity feed? I suspect the OEM fuel shutoff. However, in this case, the filter was full and it runs at least 10 minutes before this occurs. I have removed the fuel cap to test. There is no vacuum, and no difference when I test. I understand these use a standard automotive coil, such as from a 70s Ford F150. I'm just reaching out for ideas I may have missed before I go slapping new parts on the machine. Edited July 5, 2023 by Pete D Share this post Link to post Share on other sites
peter lena 8,631 #4 Posted July 5, 2023 @Pete D agree with @ri702bill on that advise , would also check over any related connections , fuses , possaible wire chafing , might be just enough time to , ehpose a short or cracked connection . recently sold a tractor with nemerious electrical issues , back of dash was packed with rotted grass on all related connections , plug ins were cracked , shorting . pete 1 Share this post Link to post Share on other sites
Pete D 83 #5 Posted July 5, 2023 Thanks, @peter lena. (Great name, btw! 😉) I had the dash out when I bought it & cleaned all of the dried debris. Everything looked OK, but I'll pull it again and check all of the connections again. I guess I should wire brush whatever may need it, and use dielectric grease upon reassembly while I'm at it. 2 Share this post Link to post Share on other sites
peter lena 8,631 #6 Posted July 5, 2023 @Pete D wiring related issues / electrical can be a trip, often use an alligator clip leade wire to jump over areas . think your consistant short time failure , can leade you to it . pete 1 Share this post Link to post Share on other sites
ri702bill 8,327 #7 Posted July 5, 2023 4 hours ago, Pete D said: Thanks, @ri702bill. I need to buy an inline spark tester. I think I will do so right now. (EDIT: Arrives on Friday) I replaced all of the fuel line a month or so ago, but it seems not to fill the fuel filter well. Is there a fuel pump, or is this, as I suspect, gravity feed? I suspect the OEM fuel shutoff. However, in this case, the filter was full and it runs at least 10 minutes before this occurs. I have removed the fuel cap to test. There is no vacuum, and no difference when I test. I understand these use a standard automotive coil, such as from a 70s Ford F150. I'm just reaching out for ideas I may have missed before I go slapping new parts on the machine. CAREFUL - these may LOOK like a car coil, but............ You NEED the one with the internal resistor to keep from toasting the points in short order!! There are numerous threads dealing with this - do a search. Some include resistance values to determine the suitability of the coil... 1 1 Share this post Link to post Share on other sites
Pete D 83 #8 Posted July 5, 2023 3 minutes ago, ri702bill said: CAREFUL - these may LOOK like a car coil, but............ You NEED the one with the internal resistor to keep from toasting the points in short order!! There are numerous threads dealing with this - do a search. Some include resistance values to determine the suitability of the coil... Thank you, @ri702bill. I have seen some of those threads, and it should not be very difficult for me to find the info. 1 Share this post Link to post Share on other sites
Pete D 83 #9 Posted July 5, 2023 (edited) @squonkp posted this, concerning coil replacement, here: Quote You need an internally resisted coil. Napa IC14 or equalvilent to what you have for suppliers is a good one. Edited July 5, 2023 by Pete D Share this post Link to post Share on other sites
Pete D 83 #10 Posted July 5, 2023 (edited) I'm guessing that this one will also work: https://www.amazon.com/Ignition-Internal-Resistor-Universal-Voltage/dp/B00WMOB1ZU/ref=mp_s_a_1_27 35,000 Volt High Output Oil Filled Ignition Coil W/ Internal Resistor. - Internal Resistance. For 12 Volt Systems Without Inline Resistor Is the condenser universal? Edited July 5, 2023 by Pete D Share this post Link to post Share on other sites
ri702bill 8,327 #11 Posted July 6, 2023 I believe not. Different for a coil ignition and a Magneto ignition.... 1 Share this post Link to post Share on other sites
ranger 1,750 #12 Posted July 7, 2023 Many cars over here 🇬🇧 used a ‘Ballast’ resister coil. These were a lower voltage coil, say 6v on a 12v system. Even though they still used’points’ and ‘Condenser’. Some had the resistor alongside the coil, others (Ford) had the coil supply from the ignition switch as a ‘Resistance’ wire, to drop the voltage. The idea was to improve starting by supplying an ‘over voltage’ through a starter motor connection to coil to compensate for voltage drop, etc when starter motor was turning. Coils for electronic ignition vehicles usually have a lower resistance, and using these on a 12v ‘Points’ system will result in rapid points, etc failure. Share this post Link to post Share on other sites
Pete D 83 #13 Posted July 7, 2023 @ranger My '72 Chevy Blazer had a ballast resistor. I was wondering whether that could work, but it's just as easy to go with the correct coil. My spark tester is supposed to arrive today, so perhaps I can test after I cut the lawn, before some in-laws arrive. Share this post Link to post Share on other sites
Pete D 83 #14 Posted July 7, 2023 So I tested with the spark checker. It is good except when I throttle up hard from idle, and the spark is weak for a few revs, and at idle speed; it backfires a bit and the spark weakens / cuts out. Both low & high speed carb adjustments were way off, so I adjusted them, and it did not cut out after idling fast for 10 - 15 minutes. I also disassembled the gas cap, which was clear, but I cleaned it anyway while it was apart. I guess I'll keep my eye on it. It seems to have been primarily carb adjustment. Share this post Link to post Share on other sites