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Subject: Troubled Ignition

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Jon Rhee (RI)    Posted 07-16-2019 at 17:28:07 [URL] [DELETE]        [Reply] [Email]  
  • Troubled Ignition
  • Hey - So I need help. I have a Ford (gas) 192 cid 4 cylinder in a Jacobsen turf tractor. It was running fine and developed a small miss. The small miss turned into a barely running engine one day and I can now not even get it started.

    I have been through the carburetor- nothing seems obviously plugged up. I took it apart and blew it down and reassembled. It is getting plenty of fuel in the bowl and does seem gassy in the intake throat on my repeated attempts to start or check the spark. The main valve in the bowl is functioning also.

    It appears that I have a strong but intermittent spark at the coil. It jumps 1/4 bright blue, but not with regularity. I have checked and replaced and rechecked the points and condenser. I replaced the insulator between the primary wire and the body of the distributor and checked the resistance. The resistor was replaced. The coil was replaced. Cap is new as is the rotor.

    I think I will run a wire direct from battery to coil to rule out shorts in existing wiring ( there are no accessories on this tractor ).

    Anything else I should look at?

    TIA - JR

    JMOR    Posted 07-17-2019 at 06:23:12 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Troubled Ignition
  • Was coil & resistor replaced before or after the troubles began? If 6v there should be no resistor and if converted to 12v, then if 12v coil, then still no resistor. Only use resistor if 12v and still trying to use 6v coil. In the case of 12v , with 6v coil, the resistor may be of too large an Ohmic value, so try it temporarily without the resistor. Verify cap & rotor are OK, i.e., no cracks or carbon trails.

    Jon Rhee(RI)    Posted 07-17-2019 at 08:47:31 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • Coil and resistor were replaced after problems developed. Tractor is factory 12V and was supplied with resistor as well. The tractor ran perfectly for over a year with the original parts in it before it went down hill. The cap and rotor look ok. The rotor was replaced along with points after the troubles began. Is there any resistance check for the cap? I will try a jumper from battery direct to coil to rule out shorts in the head end. I think my new resistor delivers about 5.5 ohms resistance, the coil shows about 6 ohms across the primary and 8,800 ohms between primary and secondary.

    JMOR    Posted 07-17-2019 at 09:29:42 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Troubled Ignition
  • 5.5 and 6 ohms both look too high by a bunch! Check meter against known resistor or with a different meter. If 5.5 and 6 are correct, then it is not going to run.

    Bob in KS    Posted 07-17-2019 at 09:25:17 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • " I think my new resistor delivers about 5.5 ohms resistance, the coil shows about 6 ohms across the primary and 8,800 ohms between primary and secondary."

    You should have a total of about 3 ohms total with resistor and coil primary

    I have seen alternator conversion kits come with 5.5 ohm resistors. They will not work satisfactory.

    6 ohms is unusual for coil primary. 6 volt coil should be about 1 1/2 ohms and direct 12 volt coil 3 ohms.

    Is 6 ohms the reading on your ohm meter with probes on coil + and - posts? If so short the probes together and subtract that reading from the 6 ohms across the coil. That will give coil resistance. It is not unusual for ohm meters to show resistance in the probes.

    8800 ohms in coil secondary winding would be in normal range. Resistance in the probes is insignificant at higher resistances.

    Jon Rhee (RI)    Posted 07-18-2019 at 16:34:19 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • I rechecked the resistor and the coil. I had to fight with the connection to the resistor but I got it down to 1.9 ohms. The coil about 2.2 ohms primary. That being said, I have a regular bright blue spark with a jumper from battery to coil. Seems slightly irregular through the dash wiring but still bright blue 1/4 arc. She starts rough then quits. Then wont really start again for a while. Ive checked the rough timing which looks good. Good compression across the board.

    Im thinking theres got to be an issue in the carburetor then, unless an intake valve can be stuck in the closed position?


    JMOR    Posted 07-18-2019 at 16:58:32 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Troubled Ignition
  • even if a valve stuck, that would result in trouble on only one cylinder & would not stop running and not cause a re-start after sitting awhile. Carb may be flooding. Be sure choke opens, float level correct, needle/seat stopping flow when closed (full bowl). Next time before starting, but having fuel tank valve open for a minute or two, close that valve before trying to start. If it starts and runs without problem for a minute or two, then that suggest a flooding problem. Carb bowl contents will be enough fuel for two or more minutes of run time.

    Jon Rhee(RI)    Posted 07-21-2019 at 11:54:03 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • Well I rebuilt the carburetor, blew it all out, changed jets, etc. Opened the tank valve then Tried starting with the tank valve closed. The engine will fire but runs only for a few seconds and its very rough. I pulled the plugs, have good spark at this point. I checked the timing which is good. Still scratching my head here.

    Jack - Iowa    Posted 07-21-2019 at 18:26:04 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • I presume that is set up with a air cleaner tubed to the carb input. You might pull that tube so there is no air restriction and give it a try then.

    Jon Rhee (RI)    Posted 07-21-2019 at 19:03:08 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • No - the air cleaner has been off the tractor. This machine went from running perfectly, to running with a slight miss, to running rough and erratically, to quitting and not restarting.

    Jack - Iowa    Posted 07-21-2019 at 19:12:52 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • It was a problem I've had and thought it a possibility.

    Now I'm wondering more serious things like the possibility the timing gear needs replaced. Does not seem like it is in the fuel or spark.

    Good Luck


    Jon Rhee(RI)    Posted 07-22-2019 at 17:31:51 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • No, I checked the timing - its right on. I did have a few short bursts of it running almost normal but for less than 3 seconds - with the tank valve off. I bought a new spark checker to further diagnose. I cleaned the spark plugs today with only a slight improvement. Has to be fuel but the carb is clean, no orifices seem plugged.

    JMOR    Posted 07-23-2019 at 04:07:10 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Troubled Ignition
  • If fuel, you should be able to make it run on ether or even for hours by spraying propane into the intake.

    JMOR    Posted 07-21-2019 at 16:38:43 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Troubled Ignition
  • A few seconds, does not register with me, unless there is a loose/bad electrical connection..

    Jon Rhee(RI)    Posted 07-24-2019 at 13:29:50 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • After ripping my hair out for another week - I decided on a long shot in the dark. I replaced the condenser (again) with one from Napa. She's back running smoothly again. When the tractor first quit I replaced the points and condenser. No change in performance. Obviously the condenser was bad right out of the box. Then followed 2 weeks of suspecting and proving out other parts. The spark even looked great, but it must have been just erratic enough from the bad condenser that is was misfiring on all 4. Thanks again to all for your help.

    JMOR    Posted 07-24-2019 at 14:09:25 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Troubled Ignition
  • glad you got it running

    Jon Rhee (RI)    Posted 07-19-2019 at 08:37:31 [URL] [DELETE]        [Reply] [Email]  
  • Re: Troubled Ignition
  • Good tip - I will check those items. I did see fuel on the bottom of air intake, so I know fuel is getting Into the carb. Hadn't considered flooding. The valves and seats were all replaced last year, so its good to know that it would not likely be the problem. I'll post back later. Thanks!

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