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Subject: weak spark at plugs

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Greg    Posted 06-12-2020 at 08:58:58 [URL] [DELETE]        [Reply] [Email]  
  • weak spark at plugs
  • Sorry this is a long one. 52 8n side mount distributor. Has been running rough lately. It runs fine after a few minutes would act like it is choking up and stalls. Will start after a little while and seems to run ok. Kept getting worse. I did find a blown head gasket. Pulled head had it surfaced and reassembled. It ran much better but was still having the symptoms mentioned above. I had a 12 volt conversion kit for years so put it on thinking it might help having all new harness. It seems to be worse now. I put new points condensor distributor cap and rotor copper core wires and plugs. I seem to get good spark at points but weak at the plugs. I even tried other coils I had around. Good fuel flow. I even put another carb I had still acts the same. I need help desperatly. Any suggestions.

    Bruce(OR)    Posted 06-12-2020 at 20:56:11 [URL] [DELETE]        [Reply] [No Email]  
  • Re: weak spark at plugs
  • 12V conversion with modern ign wires and .045" plug gap running an internal resistor coil?
    Your swapping all kinds of electrical and I wonder about your carb adjustment? vacuum leaks?
    If you desire a hotter spark at the plugs, try backing the coil wire off the internal coil connection just about 1/8 inch. That will effectively increase the coil output due to the additional air gap that needs to be overcome. Back it out too far and the engine will die.
    Chances are the choke operation is making it nice and rich to run cold.
    It is also a cold engine and has not had time to expand such as the intake manifold to the head. Gasket leak causing a vacuum leak?

    Gasket leak causing a vacuum leak is my guess.
    Then again the batteries are dead in my crystal ball so that is just an official SWAG. Others with far and vast more knowledge and great experience will be along shortly.

    Greg    Posted 06-13-2020 at 05:57:51 [URL] [DELETE]        [Reply] [No Email]  
  • Re: weak spark at plugs
  • New copper core wires. I am running the external resistor that came with the kit and an internal resistor 12 volt coil. Plugs are still gapped at .025. Plugs are autolite I think 261. I will try backing off coil wire today. Thanks will let you know

    TheOldHokie    Posted 06-13-2020 at 07:36:47 [URL] [DELETE]        [Reply] [No Email]  
  • Re: weak spark at plugs
  • You have a 12V coil and dont need or want the external resistor. Remove the resistor.

    TOH

    Greg    Posted 06-13-2020 at 10:20:55 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • Took resistor out of the circuit. It is still doing the same thing. It acts like it isn't getting enough fuel. At first have to hold choke closed about half way to keep it running, but runs rough and sputters. After it warms a little I can let choke go it still runs really rough and sputters at low RPM.If left like that after a few minutes it will stall. I can restart holding choke closed. Will not run on fast idle or above. I checked gas flow to carb. It is getting plenty of fuel. I even changed out to another carb I had does the same thing. This was happening before 12 volt conversion. I did put a new distributor on last year.

    TheOldHokie    Posted 06-13-2020 at 10:52:46 [URL] [DELETE]        [Reply] [No Email]  
  • Re: weak spark at plugs
  • You say it has weak spark. Fix that first. Quit guessing. Get a spark tester and use it to measure spark at coil and all 4 plugs.

    TOH

    https://shop.advanceautoparts.com/p/performance-tool-hi-energy-ignition-tester-w84600/9020659-p

    Greg    Posted 06-13-2020 at 12:55:19 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • OK got the tester. coil is showing spark out past the 2.0 setting bright whitish blue. Checked plugs 4,3,and 2. Same spark witish blue at standard ignition setting. The screw on the tester is rather soppy loose in the tool. It almost appears to have intermitent spark on all 3 plugs I tested. I checked and cleaned the points before I tested.

    Greg    Posted 06-13-2020 at 12:57:21 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • Also running without choke but barely. Has smoke coming out of tailpipe and can smell burning really rich

    TheOldHokie    Posted 06-13-2020 at 15:26:06 [URL] [DELETE]        [Reply] [No Email]  
  • Re: weak spark at plugs
  • Pull the plugs - if running rich the color will tell you.

    TOH

    Greg    Posted 06-14-2020 at 12:13:50 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • Update: Went out to tractor a little while ago. On a whim I pulled the condensor out and put in a condensor from an old Bolens 1054 tractor(tra 10d motor). It now starts pretty fast instead of turning over for a while with choke out.It actually idles pretty decent with minimal sputtering and don't smell the gas rich exhaust now. It will go on fast idle as well with a miss here and there. Full throttle and it misses with occasional backfire and will not get up to full speed. At fast idle it still lacks power. Am I right to assume my problem could be a bad condesor? If so what is the best one to buy. The one I took out was not that old but seems to have failed.

    Greg    Posted 06-13-2020 at 17:47:48 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • It is running rich. What is happening when I can get it to run it is very choppy acts like it wants to stall. Then it will fire again and push out the smoke. I can actually smell a gas undertone while it is running

    Greg    Posted 06-13-2020 at 11:07:49 [URL] [DELETE]        [Reply] [No Email]  
  • Re: weak spark at plugs
  • I made a crude spark tester that is how I came up with weak spark. I am on my way now to pick up the tester you sent a link to. I will check and get back with you. Thanks for your help.

    Greg    Posted 06-12-2020 at 09:19:09 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • I forgot I did check compression all cylinders are 120 or above

    Greg    Posted 06-15-2020 at 19:16:53 [URL] [DELETE]        [Reply] [Email]  
  • Re: weak spark at plugs
  • Just an update. Finally traced the problem thanks to The OLD Hokie. The problem turned out to be the condenser. I picked up a new one put it in this morning. Cut 9 acres of grass no problem. Glad to finally have my tractor running right again.

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