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How to jump a solenoid on a lawnmower, step by step

Sometimes the Lawnmower might be taking agitated starts and maybe not completely start on the flip of your key. You have just gone through all the tests, and all major components such as sparkplugs, ignition coil, carburetor, fuel supply, and lubrication system are working fine. But the mower is still not starting. Further diagnosis points to two possible causes, a faulty starter motor or a bad solenoid. One more thing worth mentioning is that a completely discharged or old disintegrated battery might also be the cause.

How to jump a solenoid on a lawnmower, step by step

  • Step 1: Turn the ignition switch on
  • Step 2: Locate the lawnmower solenoid
  • Step 3: Find the relevant terminals
  • Step 4: Clean the carbon and rust deposits from the terminal
  • Step 5: Jump the solenoid

Before learning to jump the solenoid, it is important to go through the various diagnosis steps. Understanding the working of the circuitry helps with this.

Diagnosing the lawnmower problem

Before starting with jumping the solenoid, it is a good idea to diagnose your lawnmower problem to ensure that you fix the real problem. Jumping the solenoid is easy and quick. But to do it correctly, it is important to understand why and what you are doing. The main starting circuit consists of different switches, a key, a solenoid, a starter motor geared to the engine flywheel, and a battery to power these all up.

  • Switches: Sensors ensure all safety requirements are met before the Lawnmower can be started. For example, the brake switch ensures that the brake is engaged and the Lawnmower is in parking mode.
  • Starter Key or button: With the key or button, the Lawnmower can be started. It has the indication of ON and Power on it. It allows the current from battery to solenoid and from solenoid to starter motor.
  • Solenoid: An electromagnet present after the battery relays the current flow from the battery to the starter motor. A click sound is generally noticed when the solenoid engages.
  • Starter motor: When we need to start the Lawnmower, the engine needs an initial push to intake air and gas and get to its first spark. This action is performed by the started motor geared to the flywheel or crankshaft of the engine.
  • Battery: It provides the potential difference to run all electrical components. Even the sparkplug and coil get energy from this battery.

The Lawnmower’s inability to start can be caused by one or more of these components malfunctioning. In short, directly, a solenoid cannot be blamed. To be clear on whether or not to jump a solenoid, the diagnosis part is important. If you want to be quick and already know the reasons, you might like to skip to the step-by-step guide.

  • Check the battery: Using a Digital Multimeter, check the battery’s voltage by connecting the multimeter’s with the battery’s positive and negative terminals. If the voltage from the battery is not 12 V or greater, the battery probably needs a recharge or replacement.
  • Connections and fuse: Turn the knob of DMM to continuity. Touch the connecting wires from battery to solenoid to starter motor and check the continuity. Check the fuse that is often present before the solenoid.
  • Solenoid check: Connect the solenoid to the ground and terminal of another battery and check the terminals’ continuity (the two large terminals on top of the solenoid). The clicking sound heard upon turning the start switch indicates a properly functioning solenoid. Jumping a solenoid is also a diagnostic procedure for solenoid health.
  • Starter motor: If a clicking sound is heard when the starting key is flipped, check the voltage of the motor terminals. If the voltage is good and the engine is not starting, the motor has probably failed. A whirring sound indicates that the gear from starting motor to the flywheel has worn out.

Suppose the diagnosis shows that the solenoid is malfunctioning and you do not have a spare one. The easiest and quickest way is to jump to the solenoid. There is no harm in this procedure because the solenoid is just a relay that allows momentary current to flow when required.

How to jump a solenoid on a Lawnmower, step-by-Step Guide:

Tools Needed:

These are a few basic things that will be required to carry out the jumping procedure.

  • Metal screwdriver
  • Sandpaper
  • Jumper cable
  • Digital Multimeter
  • Emergency Battery pack

• Step 1: Turn the ignition switch on

Turn the ignition key to the ON position. When you turn the key to start and hold, the engine tries to start but fails. This indicates poor solenoid or battery. 

• Step 2: Locate the lawnmower solenoid

  • Locate the battery: First, locate the battery either under the seat or under the hood.
  • Follow the wire: Track the wire from the positive terminal that ends up to a cylindrical structure with either 3 or 4 wires attached to it.
  • Solenoid: This cylindrical component is the starting solenoid.
  • Type of solenoid: The three-pole solenoid has a common ground and is connected to the mower’s body. The four-pole solenoid has a specific terminal for the ground as well. 

• Step 3: Find the relevant terminal

It is straightforward to find the copper post that connects the battery’s positive terminal to the starter motor’s positive terminal. These terminals are bigger compared to the positive and negative of the solenoid. And usually, the copper-brown color also indicates the ones that need to be jumped.

• Step 4: Clean the carbon and rust deposits from the terminal

  • Check the battery volts: It is important to check the battery before proceeding further. Use a Digital Multimeter to check if you measure above 12 Volt. If it is less the battery needs to be recharged first.
  • Clean the terminals: If the battery is good, use sandpaper to clean the solenoid’s terminals.
  • Enhance the accessibility: If the solenoid is not easily reachable, use the wrench set to remove it. Clean it and attached the jumper cable as an extension.
  • Reassemble: Place the solenoid back, keeping the extension accessible.  

• Step 5: Jump the solenoid

Using a metal piece, a metal screwdriver can do the job, connect the two copper posts. This needs to be done with the key in the “ON” position.

This should start the mower the same way as it was when you were using the key. Sparks will be produced when the jumping is performed. This is nothing to worry about. Continue the procedure until the Lawnmower starts (also with a key you have to try again sometimes).

Jumping the solenoid is not a complicated job, nor is it harmful to the Lawnmower’s health. This is a handy procedure that is good to know. It will help situations where you might have ordered a new coil and the shipment is delayed. Having knowledge on how to jump the coil will save you a lot of effort and time.

Precautionary measures

  • Safety Equipment: Where applicable use proper safety goggles, gloves, and the suit should be worn.
  • Keep distance from a flammable source: The jumping will often cause some sparks, so any flammable fluid should not be present nearby.
  • Battery recharge: If the battery needs to be charged, try to do it in an open or well-ventilated environment. Depending on the battery, some of the gases released during recharging can be harmful.
  • Insulation from Electric shock: Use proper insulated boots and gloves when you work near the spark plugs. Check the insulation of all wires. Use some insulation tape if you find damaged wires.

Related Questions

1. What does it indicate if the mower starts when the solenoid is jumped?

Suppose you had not performed the diagnostic already and wanted to save time. Upon jumping the solenoid, the mower starts. It indicates that the solenoid in the starter circuitry is not working correctly and need to be replaced.

2. What if the Lawnmower does not start even upon jumping the solenoid?

If jumping, the solenoid does not work. Check the motor, battery, and lose connections. In most cases, this will lead you to the culprit. Still, there is a chance that any of the connecting wires got damaged, and checking the continuity is the best idea.

3. What is the difference between a jump start and jumping a solenoid?

Jumpstart is generally used when the battery had died, and another battery pack is used to provide power. In that case, you can use the key to start the mower. However, if the battery is good and upon turning the key, the mower does not start. Rather than just puffs to start, jumping the solenoid is the remedy. This is connecting the starter motor directly to the battery.

4. What method should be used to clean the terminals?

Medium grit sandpaper is a good method to clean any corrosion and carbon deposits. A soft wire brush is also a good way to go. But beware that heavy abrasive processes such as grinding should not be used. The reason being, it can damage the threads, connectors, and also the solenoid itself.

Final Remarks

A solenoid is a basic component of the lawnmower starting system. Its poor performance can lead the owner to worry. If a proper diagnosis is performed and the root cause is the solenoid. If you do not have a spare, jumping is the easiest, most convenient, and time-saving way. The method is not only a solution to a problem but will also act as a confirmation, whether or not the solenoid is causing the failure. In case you do not know how to jump the solenoid, this blog will help you.