Re: Farmall not firing

Posted by John T on November 20, 2005 at 13:50:14 from (66.244.90.98):

In Reply to: Farmall not firing posted by railroadgoat on November 20, 2005 at 12:52:42:

Goat, sounds like you done went n replaced most common causes of non firing, that makes my job harder. Make sure the points are gapped correct n are opening n closing as the distributor shaft rotates?? Since you didnt mention a new switch, check that first by hot wiring the coil (see below) and checking the voltage on the switches output down to the coil.

You need to see if at least the coil is firing independant of the cap n rotor n plug wires n plugs etc. Remove the coil wire from the cap (leave coil end intact) and place that bare end to within 1/8 inch from tractor steel, turn her on n crank her over, n see if a good visible blue spark jumps that gap???????

If the coil wire is producing a good blue spark (should each time points break open) but NOT any plugs, its a plug or plug wire or cap n rotor problem or the wrong cap or its not on register to the distributor. The cap can be off when youre checking spark at the coil wire end to observe that the points are gapped proper n open n close as the distributor rotates.

If the coil wire isnt even firing you may wanna make sure the condensor or its wiring to the points isnt shorted somewhere??? If in doubt about the condensor and the points are opening n closing n sparking a lil each time, REMOVE THE CONDENSOR wire from the points n see if the coil fires then????? If it fires with the condensor removed its bad or shorted or its wiring to the points is shorted, get a new one. ALSO make sure the points wiring or its spring isnt shorted somewhere???

Nowwwwwwwww if the coil wire is sparking you need to see if any plugs are, have them removed n wires attached but sides grounded n see if they are firing as shes cranked over??? If not, remove the plugs n see if the bare plug wire ends 1/8 inch away from tractor steel will fire??? If the bare wire ends fire but not the plug, its bad or isnt getting a good ground.

If noooooooo plugs or plug wires fire but theres still good fire out the coil wire bare end to steel, inspect the cap n rotor thoroughlly for cracks or carbon or moisture. You gotta also make sure you got the correct cap n its in register on the distributor, but it should have that locator tab only allowing it to fit one way.

If the coil wire isnt even firing and the points are gapped proper n open n close as the distributor turns and the condensor or wirign isnt shorted (remember to try it with no condensor atached to see if its bad per the above) then to save me a ton of time and even though much of its a repeat of that above and you already have new parts, I will paste my entire standard troubleshootign procedure for non firing. As it will show, you gotta have voltage to the coil so try easy simple things first LIKE CHECK THE IGNITION SWITCH and/or try n hot wire it by running a hot wire direct to the coils high input (NOT to distributor) terminal n see if she fires then ????? If she fires when you hot wire the coil BUT NOT OTHERWISE check the ignition switch and power to it and the wiring form the switch down to the coil.

YOU MAY JUST HAVE A SWITCH PROBLEM !!!!!! Sice you have so many new parts I would try that FIRST (inspect it n try to hot wire the coil) Its switch contacts may be burned or spread or resistive.

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 badddddddddddd. Check them BOTH.

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

John T Nordhoff in Indiana, retired electrical engineer who usually lurks over on the Mother Deere boards versus over here on the “dark side”.

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