How to Check an Unresponsive Ignition on a Murray Electric Start Lawn Mower
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The ignition circuit on an electric start lawnmower has several components. To check it, you must insure that each component is working correctly.
Check the battery. You must be certain the battery is in good condition and we will assume that this is the case. Still, even with a fully charged battery, the voltage has to go from the battery terminals into the cables, so as well as confirming the battery is "hot", it is necessary to make sure both the positive cable connector is tight, and the ground cable and the frame grounding connection are tight and not corroded or shorted out.
Check the solenoid switch. After it is determined the battery is sending voltage through the cables, the next step in the circuit is the solenoid switch, usually located mounted on the frame near the starter motor in the engine compartment. This device contains an electromagnetic switch that closes contacts when it is energized by the ignition. It is about 2 inches by 1 1/2 inches, with two large brass studs for the starter cable, and two small screw studs for the ignition wires, and may be round, or oblong with rounded edges, and made of high impact black plastic with a metal base. By using a copper wire to "jump" the two smaller terminals, you can close the contacts on the starter circuit. You should hear a fairly loud click and the starter motor should turn when this is done. Take care not to short either terminal to a grounded part of the mower, and be aware the 12 volt current will spark when it is contacted.
Check the safety switches. If you have succeeded in getting the starter motor to turn by jumping the solenoid connections, the primary starter circuit is good, and the problem is either in the ignition switch or the safety devices on the mower. Most electric start mowers have three safety devices. One is mounted under the seat, so that the machine can only be started with the driver seated. Another is usually on the clutch/brake linkage under the deck beneath the clutch pedal. The third is located either on the mower drive belt linkage under the frame on the right side (seated) of the mower, or in the electric mower clutch circuit if the mower is so equipped. Each of these has a plastic insulated plug with two wires going into the device, and a temporary jumper may be installed into them one at a time by unplugging each one and pushing a piece of copper wire under the terminal on the end attached to the wires. If you do not have any luck finding a defective safety device, the problem is narrowed down to the ignition switch itself.
Lift the engine housing cover as you do to check the oil, and look immediately behind the ignition switch on the firewall of the mower. The switch component is on the back of the keyface, and will have a number of wires running to it, usually four. The primary voltage wire will be the largest, normally it is red, and often is found in the center. The other wires will be attached to terminals situated around the outside of the switch. Jumping from the primary wire to each terminal will result in different effects, one energizing the ignition circuit, one the starter motor, and on some mowers, another the lights or other accessories. If you can jump these terminals and the starter motor turns, you have probably located your trouble, and will need to change the switch.
This article is written from most to least likely in regard to the cause of the problem. Take care to be certain that the test does indicate the status of each device, so that you do not end up buying more parts than you need to fix the mower.
If you have a multimeter, jumpers and other "shade tree" techniques can be avoided, and these compact devices are available for less than $20.00 at home centers and other stores. It takes a little effort to learn how to use them, but they come in handy in many home and auto repairs.
Make sure all attachments and drive components are in the neutral position when performing these test.
Look at the mower deck, belts, and pulleys while you are checking, it might be a good time to do other maintenance while you are checking the electrical system.
Even though the electrical circuit is only 12 volts, jumping the terminals and working on connections with a wrench can cause serious sparks or electrical arcs. These arcs can melt steel, so they deserve respect.
Never jump the starter or solenoid without a person at the mower controls, the mower and drive system in neutral, and the wheels chocked.
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