Bizarre no spark

[ratface]

I am going crazy! Brief history, great running tractor always starts, Rewire years ago to one of JMOR schematics from scratch, all new wiring, 12 side mount internal resistor automotive style coil. I was mowing on 100 degree day, radiator started smoking like in the movies, drove it back to barn , Loud thumping noise. Shut it off. Next day noticed fan belt shredded and hanging on by a hair. Started easily and noticed thumping noise, removed fan belt and noise gone, suspected water pump, replaced and reassembled. Tried to start, no spark. Verified with spark tester on all four. I did clean the coil connections with hood off. Replaced coil. No change. I might add that the old coil tested at 4 ohms primary and 9 secondary, all within specs because the new coil measures exactly the same! 12 volt test light on negative battery terminal to distributor contact going to coil negative with switch on does not light up, while cranking does not flash. It should light up there and it dose not. I have not gotten into the distributor yet, I only replaced the water pump and got no spark/no start. Other than cleaning the coil contacts I did not change the electrical system initially, I did swap coils but that is obviously not the issue since they ohm out identical. Nonetheless I am at a no spark/no start situation with no clue as how to proceed, please will entertain any suggestion at this point!!!!!

 

[JMOR]

is there voltage to the other coil terminal? if yes, verify that insulator on screw going thru side of distributor has not failed and thus making a short to housing.

 

[ratface]

is there voltage to the other coil terminal? if yes, verify that insulator on screw going thru side of distributor has not failed and thus making a short to housing.

JMOR, just to clarify, it's an automotive style coil, positive and negative post on top, when I flip my toggle switch to on there is voltage to the positive post. The negative side has no voltage with key on or while cranking. The coil negative short wire
runs to the little stud coming out the side of distributor. Is that the stud you want me to check the insulator on? (BTW, I tested the short wire for continuity and it checks out good.)

 

[Jim.ME]

JMOR, just to clarify, it's an automotive style coil, positive and negative post on top, when I flip my toggle switch to on there is voltage to the positive post. The negative side has no voltage with key on or while cranking. The coil negative short wire
runs to the little stud coming out the side of distributor. Is that the stud you want me to check the insulator on? (BTW, I tested the short wire for continuity and it checks out good.)

Unhook the wire from the - terminal on the coil. Does it show power on both small terminals when you do that? If so it means the points are closed when you are checking or there is a short to ground after the coil. The short could be in the insulation stack at the side of the distributor.

 

[ratface]

I am trying suggestions as you guys post them. Today is the last day I have to spend some time on it for about a week. Jim, If I unhook the wire to the negative coil post from bottom of distributor stud yes indeed there is power on both coil terminals with that wire unhooked. coincidently the points were wide open. I also did a continuity test from the small stud exiting the distributor bottom to the top distributor interior plate where the points sit, and it has positive continuity, Am I correct then based on JMOR and JIM that there should not be continuity between these two points?

as an FYI, I get 12.22 volts at the positive coil stud., Keep them coming guys, its like having you gius standing here, much appreciated!

 

[Jim L WA]

It also may be a shorted condenser. Easy to prove. Just disconnect it and see if the ground is gone from the side terminal.

 

[ratface]

You guy's are just awesome. You nailed it from the first response. Tractor is purring like a kitten again. I had to run a new wire and just eliminate that screw and fiber bushing being careful to stay away from the centrifugal weights underneath. I slipped the plug thru the wire oriented toward the distributor body along with some shrink wrap. I will put a dab of silicon around the plug and incoming wire. The fiber plug was intact but there is a small square fiber barrier that was dry rotted and must have been allowing the short of the springy metal conductor. I must have disturbed it when cleaning up the coil connections by pulling on that wire and it crumbled from age. Thanks to you all for the great on point responses. I could have replaced everything in the distributor and would had still had the same issue. I would not have looked at that fiber barrier had it not been for you guys! Thanks for saving me, again!

 

[JMOR]

Some will call it a "riggin", but it will get you by.