Faultfinding String Trimmers (Strimmers)

 Just created a basic troubleshooting checklist on the Medium website here:

Troubleshooting That Problem String Trimmer!

 

Why Doesn't My Power Tool Startup?

When a power tool won't power up there are various causes of failure. but troubleshooting should be done in a methodical order, the main thing though is to check the obvious first!

Equipment Needed:

Some screwdrivers, flat and Phillips head
Continuity meter or multimeter to trace continuity from the plug to the motor.

A non-contact voltage detector (optional). These devices glow when the tip is held close to a live cable

Important !!!

Remember to avoid shock, disconnect the tool from the mains supply before troubleshooting!!!

Troubleshooting: 

 ● It may be obvious but ensure the socket outlet isn't faulty, try the tool in another outlet to see if it works.

● Check whether the overload circuit breaker if fitted on the tool has activated. This happens e.g. on a table saw when the motor is stalled. To reset you need to press a button. The breaker may need a couple of minutes to cool down before resetting

● If plug is rewireable check for loose screws at plug pin terminals, loose fuses etc. 

● A common cause of failure especially with drills and other hand held tools is one or more broken wires in the power flex caused by metal fatigue in the cable (like when you break a paper clip by bending it backwards and forwards) , this usually happens where the cord leaves the plug or where the cord enters the tool. If you have a non-contact voltage detector, you can use it to trace the break from the plug to the tool. Plug in the tool and hold the tip of the detector at the plug, it will glow here but as it is moved down along the flex it will stop glowing after the break (If the break is in the live core of the cable)

● Sometimes it is possible to detect where a break is in a flex by stretching it, the flex will narrow in the region of the break

● If you still can't trace the fault, unplug the tool. Open it. Check the continuity from each pin of the plug to the switch in the tool.

● A faulty on / off switch can prevent the tool from working. Use the continuity tester to check this

● Loose spade terminals on switches may cause intermittent operation

● Tools with green and red start and stop buttons may have a faulty relay

● The brushes in the motor may have worn down

● The armature or field coils of motor may have gone open circuit. The field coils can be checked with the continuity meter

Why Won't my Lawn Mower Start?

Lawn Mower Won't Start?

As the days lengthen, and temperatures rise, the grass cutting season isn't far away. So you drag your mower out of storage over winter, fill the tank and pull the cord..., and pull it again....and again....and of course nothing happens - Well that's typical!

If you leave fuel in the tank over winter, the carburetor can get gummed up with varnish deposits, jets get clogged and small delicate parts can seize. Ideally you should run the engine dry before overwintering and/or use a fuel stabilisation product such as Stabil.

Engines need fuel and a spark to run, plus good compression (the engine needs to hold pressure when mixture is compressed)

Checking the Spark Plug

First check the lead is pushed onto the plug properly and this wasn't the cause of non-starting. Move the mower to the shade so that it's easier to see a spark, remove the spark plug and re-attach the lead. Leave the threaded part of the plug in contact with the engine block and  pull the starter cord. The chances are that you won't be able to see the plug from your vantage point behind the mower, so an assistant may be able to aid you by pressing the plug against the block (using a plastic bottle or whatever to avoid shock if the plug lead is damp). The spark should be bright and blue.

When replacing a plug, make sure there's nothing on the threads such as dirt or grit, and make sure it isn't cross threaded by screwing in by hand before tightening with a plug wrench. If the plug is cross threaded, it will be difficult to turn by hand.

Fuel  Starvation

This means the engine isn't getting fuel. On engines with the tank above the carburetor, fuel first flows to a device called a float bowl. This is like a toilet cistern and prevents fuel just running into the carburetor. The bowl fills and once its full, a float (which functions just like the ballcock in a toilet cistern) cuts off flow. Sometimes the intake to the bowl can get clogged or the filter in the fuel line can be blocked, either of which can cause fuel starvation. When you remove the bowl, petrol should flow freely and stop flowing when you push up the float (use a jar or tin to catch fuel).

Another cause of fuel starvation is a clogged main jet. You can get carburetor cleaning aerosols which have a straw just like on a can of WD40. You insert the straw into the jet and press the button on the aerosol, the spray flushes the jet. If you have an air compressor, you could try using the a blow gun attachment to blast air through the jet. Avoid poking nails, wires or other objects through it, which could damage the jet which is made from brass.

Compression

Check the plug is screwed in tightly. Don't over tighten as you can damage the threads.

Read my full version of this blog post on DenGarden.com. It has lots more info on lawn mower troubleshooting with loads of pictures and goes into much more detail:

 

https://dengarden.com/landscaping/Why-Wont-That-Lawnmower-Start