Craftsman 28906 Professional Shop Manual page 7

CRAFTSMAN
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M is connected to the magneto by a yellow wire,
G is connected to ground by a green wire, and
A1 is connected to the after fire solenoid.
NOTE: In the OFF position, the magneto primary
windings are grounded, disabling the ignition
system. The altenator output is shorted to
ground and the after fire solenoid looses its
power from the B terminal. This turns-off the fuel
supply.
Symptom-enqine runs with key in OFF position:
The key switch is not completing the path to
ground either because of an internal fault or a
bad ground connection elsewhere in the har-
ness. Check continuity between M, G, and A1
terminals with key switch in OFF position.
Check green wire for continuity to ground.
Symptom-loud "BANG" when key is turned to
the OFF position: The after-fire solenoid is not
closing, either because it is physically damaged
or the power is not being turned off. Check for
power at the solenoid. Check continuity between
G and A1 terminals. Check for no continuity
between A1 and the B terminals.
NOTE: If the engine is at an idle when the key is
turned off, fuel is drawn into the engine through
the idle ports of the carburetor by-passing the
fuel shut off solenoid. The raw fuel will travel
through the engine and ignite in the muffler
causing an after fire.
Symptom-Enqine runs 3-5 seconds after key is
turned to OFF position: The after-fire solenoid is
turning-off the fuel supply, but the ignition is con-
tinuing to operate. Check continuity between the
M and G terminals in the OFF position. Check
continuity from yellow wire connection all the
way to the spade terminal on the magneto.
In the START position, continuity can be found
between B, S, and A1 terminals.
Battery power from the B terminal is directed to
the start circuit through the S terminal and to the
after fire solenoid through A1.
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Symptom-No crank and no starter solenoid
click: Power is not getting to the trigger spade on
the starter solenoid. Test for proper battery volt-
age. Then check for power where the fused red
wire with white trace connects to the B terminal.
Check for continuity between B and S terminals
in START position. If power is getting to the S
terminal in the START position, the problem lies
down-stream in the starter circuit; Check conti-
nuity from the orange wire on the S terminal to
the orange wire with white trace on the trigger
spade on the starter solenoid. If it is broken,
trace through the brake and PTO switches.
Symptom-No crank, solenoid click: The problem
lies in the heavy-gauge side of the starter circuit;
battery cables, starter cable, solenoid, or ground
issue.
Symptom-Crank, spark, but not fuel: First test
for power at the solenoid, if no power then check
for continuity from B to A1 in the START posi-
tion. If power is reaching the red wire that con-
nects to the A1 terminal in the start position, the
problem lies down-stream of the key switch. A
handy quick-check is to apply power to the red
wires where they connect to the S terminal
(whole circuit) or directly to the after fire solenoid
to listen for the audible "click" that it makes when
functioning.
Symptom-Crank, but no spark: This is a highly
unlikely scenario. If it occurs after a key switch
has been changed independently of the RMC
module, this would arouse suspicion that the
wrong key switch was installed. Otherwise, the
problem lies elsewhere in the safety circuits or
engine. Do not over-look the possibility of a bad
magneto or chafed ground lead within the
engine harness.
In the NORMAL RUN position (green zone), the
B and A1 terminals should have continuity. Once
the engine is running, the alternator produces
current that tracks-back to charge the battery,
via the red wire connected to the B terminal.
Symptom-Battery does not charqe: Follow the
engine manufacturer's recommendations for
testing alternator output. If alternator output is
getting to and through the key switch, but not
reaching the battery, the fuse may have blown
after start-up. A blown fuse will disable the
starter circuit. A simple quick-test for the pres-
ence of alternator output at the battery is to
check across the battery posts for DC voltage.
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