Re: Super M Ignition: Won't run same way twice?

Posted by neblinc on October 23, 2006 at 09:54:56 from (24.123.122.114):

In Reply to: Super M Ignition: Won't run same way twice? posted by Dennis Gauge on October 23, 2006 at 09:15:40:

Here is John T's excellent troubleshooting step by step guide.
After trying this, you should check to see if it is fuel related, bad
gas, no fuel, plugged carb etc.

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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