MTD 700 Series Professional Shop Manual page 98

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Series 700 Lawn Tractor
NOTE: On all 700 series tractors:
• The M terminal is connected to the magneto by a yellow wire.
• The G is connected to ground by a green wire
• The S terminal is connected to the starter.
• The B terminal is connected to the battery.
In the OFF position, the magneto primary windings are grounded, disabling the ignition system.
NOTE: On tractors with the standard electrical system and the 8-pin OCR module; the after fire solenoid loses
its power from the B terminal. This turns off the fuel supply.
NOTE: On tractors equipped with the 7-pin OCR module; the alternator is grounded through the A1 terminal to
drain the power away from the after fire solenoid.
Symptom: engine 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 harness. Check continuity
between M, G, (and A1 if equipped) terminals with key switch in OFF position. Check the 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 (L on 5-pin switches) terminals. Check for no continuity between A1
(L on 5-pin switches) 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: Engine 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 continuing 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 (L on 5-pin switches) 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 (L on 5-pin switches) terminal.
Symptom: No crank and no starter solenoid click: Power is not getting to the trigger spade on the starter
solenoid. Test for a good battery 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 continuity
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; low bat-
tery voltage, battery cables, starter cable, solenoid, or ground issue.
Symptom: Crank, spark, but no fuel: First check the fuel tank to verify that there is fuel in it. If there is fuel in
the fuel tank, test for power at the after fire solenoid. If there is no power there, then check for continuity
from B to A1 (L on 5-pin switches) in the START position. If power is reaching the red wire that connects
to the A1 (L on 5-pin switches) 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 func-
tioning.
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