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Subject: 641 wont start (2020)

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Mike in Michigan    Posted 07-11-2020 at 08:21:21 [URL] [DELETE]        [Reply] [Email]  
  • 641 wont start (2020)
  • 641 with 6v pos side mount distributor. So over the winter I developed a gas leak at valve. Removed the hood and gas tank and did the rivet removal/screw replacement repair and put back together.

    I tried starting and it would run for a few seconds and then stop and would not restart. After researching on this forum I decided to pull the carb and clean her out. Had a little dirt in the bowl otherwise looked good. Tried starting again and now apparently no spark as it only turns over. Turns over fine. The solenoid clicks once when first press starter button. After researching decided to replace the battery even though only 10 months old and had 6.5v. New battery made no difference.

    I cleaned off all the connections around the solenoid. I noticed that the gas tank needle sits below the 'E' mark and when I turn the key on it moves up to the 'E' even though there is about a quarter tank if that helps.

    I replaced the spark plugs - no effect. I did the spark plug 3/16 gap test. Interestingly I had spark the first time but no spark after the initial test. I just bought a new coil - no effect. New condenser - no effect. I figure I'd post to the experts before I continue with replacing parts.

    I did a lot of work around the distributor a couple years back with the insulator, copper connector and has been running fine since (although I no longer use the tractor as I live in the burbs, probably will be selling soon).

    So where do I go from here?

    Tim Daley(MI)    Posted 07-11-2020 at 13:30:37 [URL] [DELETE]        [Reply] [Email]  
  • Re: 641 wont start (2020)
  • Mike - If you are nearby I could come over and look at your Ford 641 with you -I sent an email with my phone number.

    You could have just had the battery tested at a local shop before going out an buying a new one. New batteries can be junk out the door, mostly the cheaper bargain-house brands so don't judge performance by age -have specific gravity tested on a bench. Did you perform the fuel flow test before pulling the carb off? Are the plugs wet after cranking and no-go starting? Just replacing parts willy-nilly without proper diagnosis will only get a bunch of new parts that may or may not happen to fix a defect or until you run out of money. One issue at time. Fuel flow pass? No? Problem solve til root cause resolved. Yes, problem lies elsewhere. Wiring tested thoroughly. Distributor tuneup - points set and timed correctly? Points set = .025" +/- .001" Spark Plug gap = .027" +/- .001". CLYMER I&T FO-20 Manual and the OEM FORD Owner's Manual are your friends. Get your Essential Manuals out and go step by step -avoid shortcuts and guesswork. FYI & FWIW, the OEM 600/800 electrical system uses the 20-AMP/2-Brush 'B' Circuit Design Generator. The unit must be polarized correctly too but most likely not your problem.


    BTDC = Degrees Before Top Dead Center





    NOTE: *The 9N-10000-A generator and everything after the NAA thru Hundred Series models are 'B' Circuit Type.

    Tim Daley(MI)

    Jack - Iowa    Posted 07-11-2020 at 11:30:02 [URL] [DELETE]        [Reply] [Email]  
  • Re: 641 wont start (2020)
  • I'm going to throw this in here, just in case.

    I recently fought a strange set of symptoms on my 860. Drove it into the machines shed, could not start it to drive it out! Intermittent spark for one.

    Ended up being the distributor. Measure the point gap on all four lobes. Should essentially be the same. I had wild variations.

    Could not feel the slop from the top but once the distributor was in my hands, there was no question.

    Slight possibility but easy check.


    Jack - Iowa    Posted 07-11-2020 at 10:31:43 [URL] [DELETE]        [Reply] [Email]  
  • Re: 641 wont start (2020)
  • You are going to get a lot of advice to stop guessing and start troubleshooting. You are wasting money.

    From the sound of it you should start with the ignition. Do you have an ohmmeter? You can pick up a cheap digital for around $15.00. Not the best but probably good enough to find your problem.

    Meter in hand, measure the voltage to the coil from the switch. Should read full battery voltage. If not check the input from the battery to the switch. Check the wiring and battery cables. Are the battery connectors clean and tight? Does the cable to ground (tractor frame) clean and tight?

    Next check the voltage on the wire from the coil to the distributor. If the points are open is should read full battery voltage. If the points are closed it should read about half battery voltage. Check both ways. If the points are open and you only read half voltage, check for shorts to ground within the distributor.

    Post back after you have gotten this far.

    Good Luck,

    Jack - Iowa

    Mike in Michigan    Posted 07-23-2020 at 20:33:27 [URL] [DELETE]        [Reply] [Email]  
  • Re: 641 wont start (2020)
  • I checked and cleaned the battery connections and checked the distributor. Points were a little tight but consistent so I corrected.
    Tractor started but stopped after about 30 seconds, which is the way it was right after putting the gas tank back on.
    I still don't get any spark by putting a plug 3/16" from frame. Actually got the spark a few times when a first checked about a month ago and not since.
    Question on testing voltage. When you say coil to switch where do I place the probe on each? Does the switch need to be in the On position? Same questions for coil and distributor voltage check. Obviously I'm a novice pertaining to electrical work.

    Jack - Iowa    Posted 07-23-2020 at 21:44:48 [URL] [DELETE]        [Reply] [Email]  
  • Re: 641 wont start (2020)
  • Mike,

    Think I'll send you an email in the morning.


    Jack - Iowa

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