JD Model M No ignition spark

Maybe the cond. wire or the points spring is not insulated and touching ground ? Sometimes right where they hook together at the points they turn and bump ground.

Yours is a pretty wide open question so I will just copy n paste my entire long winded n complete Troubleshooting Procedure for non spark. Once you have good voltage to the coil with a good set of closed working points run my test lamp procedure listed below for voltage over on the coils other output (to distributor) terminal where a test lamp ought to flash on n off as the engine is slowly cranked over. You might try the "hot wire" to the coil trick listed below in case the ignition switch is resistive and make sure the points n condensor wiring isnt shorted somewhere. The points gotta be gapped n opening n closing of course..... ...

TROUBLESHOOTING A BATTERY POWERED EXTERNAL COIL TYPE IGNITION SYSTEM:

PRELIMINARY CHECKS:

(A) To see if it happens to be a cap n rotor problem and to see if at least the coil is firing, remove the coil wire from the distributor (leave coil end intact) and place its bare end to within 1/8 inch from tractor iron, turn her on n crank her over, and see if she jumps that gap with a good visible blue spark????? If so but the plug wire ends (from wire end to 1/8 inch to frame) or the plugs themselves don�t fire, its a cap n rotor or plug wire problem. If the coil wire isnt even sparking, see below.

(B) Next open the cap and see that the points are gapped correct and indeed opening and closing as the engine is cranked and the distributor shaft rotates and MAKE SURE THEY ARE NOT BURNED OR PITTED OR CARBONED UP BADLY !!!!! !!!!! If so, running a point file between them to clean them up might make her run again HOWEVER that�s only a temporary cure, so if that cleaning makes her spark, INSTALL N GAP NEW POINTS. In the event they appear good but only gray oxide coated, non abrasively clean/buff/polish them using say a dollar bill or shop cloth etc. and see what happens.

MORE TROUBLESHOOTING IF ALL THE ABOVE STILL FAILS TO MAKE HER SPARK

1) THE VERY FIRST THING YOU GOTTA HAVE is voltage to be present on the coils high supply (NOT to distributor) terminal when you turn the Ignition switch ON. If not she cant ever fire, but in the event the ignition switch or circuit/wire down to the coil or any Ballast Resistor is bad or open, you can HOT WIRE it by jumping a hot ungrounded battery voltage source to the coils high input supply (NOT to distributor) side n see if she runs then???? If she fires hot wired, you could have a bad ignition switch ((That can happen, when Ignition is on, the switches IGN terminal must turn hot)),,,,, ,or an open Ballast (if it has one) or a bad/open wire from switch to coil.

If the switch is good, if you turn the ignition switch on and place a test lamp on the coils high (NOT to distributor) terminal SHE MUST LIGHT UP. If not again, look for an open Ballast Resistor (if it has one, it should read around 1.25 to 2 ohms across its terminals) or bad/open wires from the switches IGN output down to the Ballast (if it has one) and distributor.

2a) When the Ignition switch is turned on, voltage should appear on the coils high input side. That would be 6 volts on a straight 6 volt system or 12 volts on a 12 volt non external ballasted system, or around 6 volts on a 12 volt system that used a 6 volt coil plus an external Ballast Resistor and the coil is good and the points are closed and they and ALL wiring is good.

2b) To insure the coils low voltage primary winding is not bad/open, use an ohmmeter and measure its DC resistance between its lil + and -terminals. If its an open circuit (no continuity) its bad/open and will NOT work. It should measure around 1.25 to 2 ohms or so if its a 6 volt coil and maybe 2.5 to 3.5 if its a 12 volt internally ballasted coil. NOTE CAUTION have all leads and any voltage source DISCONNECTED FROM the coil for this simple primary winding continuity test. 3) Next, place your voltmeter or test lamp over on the coils other low to distributor terminal side, turn her on and crank the engine over.

4) A test lamp there should flash ON (when points are open) and OFF (when points are closed) as the engine is cranked slowly.

5a) If the lamp never comes on there, the coils primary is bad/open,,,,, ,,,,or the points are never opening,,,,, ,,,or theres a shorted/bad condensor (remove its lead to points and see if lamp comes on, if so, bad shorted condensor or its wiring),,,,, ,,or the points wire is shorted,,,,, ,,or the distributors side pass thru stud is grounded (use ohm meter to test that),,,,, ,,,or the points may have a shorted spring.

5b) If the lamp never goes off as engines cranked, the points are not closing or are bad,,,,, ,,or the wire or circuit is missing from the distributor to the points,,,,,or the distributors not well grounded to the tractor.

She cant fire the coil unless its low side is getting a conductive ground return path via closed points and then the circuit is open when the points open.

Be sure the condensor or its wiring is NOT shorted out and see if the lite comes on (when points open) with the condensor disconnected. If removing the condensor makes her spark, replace the condensor.

SUMMARY

Be sure the points are closing fully and open on high cam and ARE NOT BURNED OR PITTED OR CARBONED UP BADLY,,,,, ,theres voltage present on distributors high side at all times when ignitions on (or its a bad switch or open ballast or bad wiring to col),,,,, ,voltage on coils low side flashes on and off as distributor is cranked,,,,, ,,,condensors not bad/shorted,,,,, ,,no shorts in wires to points and no shorts in pass thru side out distributor stud,,,,, ,,coil has continuituy.

You may luck out n just need a new set of points. If the coil wire fires (see above) and the plug wire ends to 1/8 from frame but NOT the plugs, they are baddddd ddddd . Check them BOTH.

Good Luck n God Bless, post back any questions and your findings and any questions.

John T

Now that we know that, when you say you measured 12 volts at the coil, that tells me the points arent closed,,,,, or arent well grounded or miswired,,,,, , or the distributor doesnt have a good ground,,,,, ,,,,,or the coils primary is a bad/open circuit. Cuz if the points were wired correct in the circuit and closed there would be current draw through the coil and ballast which would only leave 6 volts on the coil versus the 12 you claimed..... ..... ....

LOOK FOR OPEN POINTS OR THEY ARENT WIRED CORRECT OR THE WIRES OPEN FROM COIL TO DISTRIBUTOR OR THE DISTRIBUTORS NOT GETTING A GOOD GROUND OR TEH COILS PRIMARY IS BAD/OPEN !!!!! !!!!! !!!!!

John T

If it has a 12 volt battery thats okay cuz now its a 12 volt system NO PROBLEM.

Now that we know what we are workign with, run through the steps of my Troubleshooting Procedure posted above and it will guide you to the problem like points or condensor or wiring or a wirign short on the points or condensor etc etc or coil etc etc

HOWEVER as I posted below and assuming the coil and ballast are good and wired properly and that the pointt are closed (as normally are) there should ONLY be 6 volts on the coil versus the 12 you claimed. THAT TELLS ME THERES NO CURRENT DRAW THROUGH THE BALLAST AND COIL AND CLOSED POINTS TO GROUND cuz if so there would be 6 volts on the coil.....

Make sure points are gapped properly and indeed fully closing????? ??? make sure the wires good from coil to distributor,,,,, ,,make sure the wire inside the distributor (from coil) is good to the points,,,,, ,,,make sure points and distributor body are both well grounded (try some lil jumpers)

On a 12 volt tractor using a 6 volt coil and external ballast system with good points closed THERE SHOULD ONLY BE 6 VOLTS ON THE COIL and if not the circuit from the coil to the distributor and thru good clsed points and to frame ground IS OPEN SOMEWHERE

Run my tests and you will find the answer, thats about all we can do for ya sittin here

PS unless that coil has a bad open primary it should have around 1.5 ohms of resistance between its lil + and - terminals and if its open theres no current draw and you will still read 12 versus the correct 6 volts on the coils input CHECK THAT COILS CONTINUITY

Let us know, best wishes n God Bless

John T