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1950 Ferguson TO20 has no spark


 
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Rickoff
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PostPosted: Tue Sep 25, 2012 9:45 pm    Post subject: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

Two weeks ago my 6 volt positive ground TO20 tractor started well and ran fine. Today I went to start it and no luck. I charged the battery to a full charge, and the starter turns the engine over nicely now. Pulling the coil's hi voltage wire from the center of the distributor cap and holding it close to the engine block while cranking the starter with ignition switch on, no spark jumped to the block. Pulled other end of wire from coil tower and checked continuity from end to end and was fine at zero ohms. Checked voltage between each of coil"s primary terminals and engine block, and also at distributor with points open, and all 3 were the same at 6.3 volts. Points and condenser have less than 12 hours service time on them, and points looked fine. Checked point gap and was correct at .022, removed condenser and bench tested it with an analog multimeter and it does appear to charge and discharge okay. Re-installed condenser, and with ignition switch on and points closed I manually opened and closed the points several times using an insulated tool, but there was absolutely no visible arcing whatsoever. Swapped condenser with the last one, which had worked fine, and still no arcing. Swapped coil with a new 6 volt replacement coil that I keep on hand, and no difference observed. Checked all wiring and it is good and connected as shown in TO20 service manual. Got dark, so I came inside to think about it, do some Internet research, and to write this. Knowing that the voltage is fine at the coil and the distributor, it would seem that amperage is low or I would see some arcing at the points as I did when I last replaced them. As stated earlier, the battery took the charge well and is cranking the starter nicely, so definitely not a low amperage battery. Tomorrow morning I'll try running a 12 gauge wire directly from negative battery terminal to coil to bypass the ignition switch, but if the problem is not the ignition switch then I will have tried just about everything I can think of and will hope you folks can give me further suggestions. Incidentally, the ignition switch on this tractor is not a key switch. The old key switch was removed by the previous owner when it failed, and it appears that he utilized the on/off toggle light switch (with no lights hooked to it) as an ignition switch, which has worked fine. In checking the wiring, I did remove the wires from the switch and tested the switch with an ohm meter, and it checked okay - open circuit when toggled off and zero ohms when toggled on.
 
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2tractors
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PostPosted: Wed Sep 26, 2012 4:08 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

If your getting fire to the coil that eliminates the switch,leaving the insulator to the distributor being shorted or either the condensor connector is touching ground.Is it a+ grd. or-?
 
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phil(va)
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PostPosted: Wed Sep 26, 2012 4:43 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

It appears you have a gremlin. Sometimes I have noticed testing spark at coil wire isn't conclusive and testing at spark plug wire is more indicative. Try putting a spark tester in line between a spark plug wire and a plug and see if you have spark. As mentioned, the insulator where the small wire comes into the distributor is something to check. I know you have tested and got no spark inside the distributor, but just for grins make sure the cap isn't cracked. Wouldn't hurt to look at the plugs, even though you don't think it's getting that far.
 
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Jerry/MT
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PostPosted: Wed Sep 26, 2012 9:37 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

What do you get on the coil primary voltage with the points closed.?
You should have battery voltage on the ignition side of the coil and almost zero volts on the distributor side.
 
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DON TX
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PostPosted: Wed Sep 26, 2012 10:09 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

Could be corrosion on the points. Pull a dollar bill between em and retry. HTH
DON TX
 
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Rickoff
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PostPosted: Wed Sep 26, 2012 3:25 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

@2tractors: As stated in the first sentence of my original post, this is a 6 volt positive ground system. I also stated that the coil tower was not throwing a spark with the high voltage wire placed near the engine block, so no way that the ignition switch can be "eliminated." I did state that there was 6.3 volts present at the coil primary terminals and the distributor connector with the points open, but since voltage is constant in this type of circuitry (other than what should come out of the coil, which is a voltage step-up transformer) the indication of correct voltage being present at the coil and distributor does not mean very much, since you can have 6.3 volts but very little amperage present if there is a partial or full short somewhere in the system that is robbing amperage. As you suggested, the distributor connector insulation could be cracked, and thus robbing amps by partially or fully arcing to ground whenever the voltage rises in the coil's primary windings. Although I hadn't mentioned it in my first post, I had checked the insulator when checking all the tractor wiring for any possible grounds. Thanks for offering suggestions, though.
 
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Rickoff
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PostPosted: Wed Sep 26, 2012 3:49 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

@phil: Thanks for posting the suggestions, even though they don't make much sense. If you remove the high voltage wire from the center of the distributor cap and place it within an eighth to a quarter inch of the engine block, as I did while cranking the engine, you will either see a strong spark, a weak spark, or no spark at all. If there is no spark visible (which was the case), then there is no way you will place that wire end back into the distributor cap and find that you have a spark at any spark plug. One does not need to purchase a spark tester to determine whether or not there is a spark, and the strength and quality of the spark is quite apparent to an observant eye. You want to see a strong, bluish spark. Just a note to those who might use my method of holding the high voltage wire close to the engine block - be sure that you use something like an insulated ignition wire holder tool when doing this test or you may receive quite a jolt!
 
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Rickoff
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PostPosted: Wed Sep 26, 2012 3:59 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

@Jerry: Yes Jerry, that's what I had when I tested. Sorry, perhaps I should have mentioned the points closed voltage reading, although it should readily be understood that when the points are closed you have a direct short to ground and thus no voltage will show at that point of the circuit.
 
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Rickoff
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PostPosted: Wed Sep 26, 2012 4:05 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

@DON: thanks for reply, but no, as I stated in my first post, the points were verified visually to be in very good condition and had less than 12 hours on them.
 
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Rickoff
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PostPosted: Wed Sep 26, 2012 4:54 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

Problem solved! As I suspected, it was the toggle switch that the previous owner had substituted for an ignition switch when the old key switch went bad. It had worked fine, and was beefy enough that after ohm meter tests showed the switch was functioning properly (with an open circuit when off, and zero ohms when on) I was not all that suspicious until after I had double checked everything else. I knew that something was obviously robbing amperage, so first thing I did this morning was to disconnect the negative cable end from the battery, and connected my digital multimeter to see if any current was flowing between the cable and the battery post. There should be NO current flowing when the ignition switch is off and no devices are in use. Sure enough, this test showed a draw of 5 amperes. I removed the ignition switch and its wires from the circuit, reconnected the battery terminal,and then ran a wire directly to the coil negative terminal from the Load connector of the voltage regulator, thus bypassing the switch altogether. The wire end, as it touched against the coil's negative terminal, gave off a visible arc, so I knew the switch had been the culprit. Sure enough, the engine started up immediately when I turned gas flow on and engaged the starter. Later on I went to the local auto parts store and purchased a well built key switch that I installed upon returning home. Also purchased a new toggle switch for lights, as I'd like to have some running lights this winter when plowing snow at night. The previous owner had removed and saved one of the old headlights, and one rear lamp. I haven't tested them yet to see if they are any good, but would like to have a pair both front and rear, so will be looking to see what I can find. Any suggestions on a source for original lamp fixtures? If so, thanks in advance.

By the way, that defective toggle switch was marked rated at 30 amps, which would seem more than adequate, but was definitely not the original light switch as it is marked "Made in China." Nearly all electrical components sold in auto parts stores nowadays are cheaply manufactured in China. Sad, but true.
 
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2tractors
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PostPosted: Thu Sep 27, 2012 4:49 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

My bad on not remembering your mentioning the 6V system at the beginning but in my defense it was a long post BUT there seems to be a flaw in your remedy of finding an amperage draw with the toggle switch which you stated checked out at ZERO ohms when on. An if there was a draw your cables would heat up and drain your battery.
 
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Jerry/MT
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PostPosted: Thu Sep 27, 2012 10:55 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

But if you points weren"t closing ......
 
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phil(va)
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PostPosted: Thu Sep 27, 2012 11:40 am    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

You must be related to the admiral...?
 
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DON TX
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PostPosted: Fri Sep 28, 2012 8:53 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

Looks can be deceiving. Doesn't take but few minutes.
HTH
DON TX
 
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DON TX
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PostPosted: Fri Sep 28, 2012 8:57 pm    Post subject: Re: 1950 Ferguson TO20 has no spark Reply to specific post Reply with quote

Glad you found the prob. Electrical probs are the hardest for me to find sometimes.
DON TX
 
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