The Lawn Mower wont start are words you don’t want to hear. Troubleshooting can be frustrating, it helps to have guide as to where to begin.

The Lawn Mower wont start are words you don’t want to hear. Troubleshooting can be frustrating, it helps to have guide as to where to begin when trying to diagnose this problem. 

I have found this section of a much larger article covering many aspects of small engines to be very helpful. There is a lot of good information why the Lawn Mower wont start or is hard to start. You may want to bookmark this page. 

Notes on the Troubleshooting and Repair of Small Gasoline Engines and Rotary Lawn Mowers 

Version 2.39 (28-Aug-07) Copyright © 1994-2007 Samuel M. Goldwasser 

--- All Rights Reserved ---

Instant troubleshooting chart - most common problems and possible causes


The following chart lists a variety of common problems and nearly all possible causes. Diagnostic procedures will then be needed to determine which actually apply. The 'possible causes' are listed in *approximate* order of likelihood. 

While this chart lists many problems, it is does not cover everything that can go wrong. However, it can be a starting point for guiding your thinking in the proper direction. 

(Portions of the following from: Chilten, Small Engine Repair 2-12 HP, (1).) 

Lawn mower will not start

This is probably the most common problem you are likely to encounter. The cause is very often the same - lack of maintenance.

Note that the assumption here is that it cranks - the crankshaft and blade rotates in a normal manner but the engine never catches.

Some larger (Briggs and Stratton) engines may have a low-oil cut off switch which will stop the engine if the oil level is inadequate. However, this is not likely on a push mower.

In the case of a recoil starter, you are able to pull on the cord and the crankshaft with the blade rotates and it feels normal but the engine does not start. If it feels like nothing is engaging, then the starter mechanism or clutch may be broken. Of course, if the cord breaks, then the problem is obvious!

•In the case of an electric starter, the engine cranks but never catches. If there is no response to the button or key, then the outlet may not be live, the battery may be weak or dead, or there could be a bad connection or bad starter motor.

If the motor spins but doesn't engage the engine, the overrunning clutch or gear could be broken.

If you are unable to pull the cord (or the auxiliary starter on one with electric start), there may be a clump of grass stuck between the blade and the deck or there could be serious internal damage, especially if you just encountered an immovable object.

However, you didn't forget to engage the dead-man bar, did you? On most inexpensive mowers this safety interlock is needed to both enable the ignition system and release the blade brake.


Most of the time, the possible causes and solutions will be similar to those where the engine doesn't start at all. So, see the following sections for more information. However, here are some specific issues dealing with engines that do start eventually and then run fine:

• Cockpit error: If you have a user manual, read it! The starting procedure for all engines is not the same. Make sure you are following the recommended starting procedure. This may not always be best but it is a starting point (no pun....).

 Number of priming cycles: The instructions on priming are often optimistic. In colder weather, twice as many presses of the primer may be necessary. However, over priming and flooding is also possible. Don't overdo it.

• Condition of gasoline: Old or contaminated gas will make any engine harder to start. If theproblem is with an engine using last year's gas, drain the old gas completely and dry out the residue in the fuel tank if possible.

If debris or water is found in the old gas, the carburetor may need to be drained and cleaned as well. Then add fresh gas (not from the batch sitting in the can since last year!).

In cold weather, the water can turn to ice inside the carburetor float bowl causing all sorts of problems including flooding of the engine.

• First start of the season: If no maintenance was done at the end of the last mowing (or whatever) season, the first time the engine is started may be tough. However, this may be a one-time problem.

Hopefully, if all the recommended maintenance was done, the first start may not be perfect. And, for float-type carburetors, after filling the fuel tank, wait a minute or so for the gasoline to fill the float bowl before pulling the cord!

Nowadays, a lot of mower/equipment is using OHV (Over Head Valve) style engines. This in itself causes many starting troubles. These engines use a compression release on the camshaft to allow for easy starting.

Once the engine has started and reaches a speed of over 700 rpm, the weight on the compression release swings out and allows the engine to gain full compression and full power.

After awhile, the valve lash/clearance begins to widen and the first thing that goes wrong is the compression release doesn't work properly causing the engine to drag which may sound to some as a dead or dying battery.

I'm sure there are untold thousands of people that have replaced batteries, solenoids, starters, switches, etc., only to find themselves going to a repair shop and letting a trained mechanic do what is a simple maintenance adjustment.

If the previous information was of help to you and you would like to view the entire article please click here .

By having a basic guide when the Lawn Mower wont start you may save yourself many hours of anger and disappointment when you find out that it was something as simple as water in the gas that been preventing the mower from starting.

This information may also save you a lot of money by not having to take your mower right away to a small engine mechanic. Remember when ever you are working on your equipment think safety first.

Hope this helps with Lawn Mower wont start.


“Keep It Simple to Succeed” lets get out there and make our lawns healthy and green!

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