Re: 656 still not starting and getting frustrated

Posted by John T on October 04, 2011 at 12:20:14 from (173.243.181.15):

In Reply to: 656 still not starting and getting frustrated posted by don656 on October 04, 2011 at 10:20:42:

Don, let me answer your questions:

""""With the ign. switch on, (but not cranking the motor) I have 12 volts from the positive terminal of the coil to ground. I also have 12 volts from the negative terminal (which is connected to the outside distributor terminal) to ground. John T says this should not be, but with the coil disconnected and sitting on a bench, there is only about 1 ohm resistance across these terminals. So, if you have voltage on one terminal, how can you not have it on the other?""""

Okay, IFFFFFFFFFF the coil is on the tractor with ignition switch ON (YES should be 12 volts on coil input to ground) and ifffffffffff its output is connected to the distributor and iffffffffffffff the points are good and closed (as they usually are when its setting there) and the wires okay from coil to distributor THERES ZERO VOLTS ON COILS OUTPUT BECAUSE THE CLOSED POINTS ARE TAKING THAT DIRECT TO GROUND AND GROUND TO GROUND = ZERO VOLTS.

HOWEVER on a bench or if the coils output is NOT conencted to a distributor with POINTS CLOSED THEN THE VOLTAGE ON OUTPUT IS INDEED 12 VOLTS SAME AS ON INPUT

SHES NEVER GONNA FIRE UNTIL THE COIL DRAWS CURRENT AND THAT REQUIRES GOOD WORKING CLOSED POINTS (i.e. zero volts on coils output) AND THEN WHEN THEY OPEN SHE FIRESSSSSSSSSSS

HERES A PART OF MY TROUBLESHOOTING PROCEDURE IF YOU TAKE THE TIME TO WORK THROUGH IT THE PROBLEM SHOULD JUMP OUT AT YOU !!!!!!!!!!!!

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.

NUFF SAID

John T

• John T's Ignition Troubleshooting

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