A full gas tank and oil reservoir are the essential first steps when checking why the lawn mower won’t stay running, but the problem could also be a dirty filter, clogged carburetor, improper Step 2. Remove the spark plug wire from the spark plug. Clean any corrosion off the battery terminals. Turn the key to the ON position and turn on the voltmeter. Place the negative lead from the voltmeter to the negative post on the battery. Place the positive lead (red) lead to the post on the solenoid that has the positive lead screwed on to it. The first thing to check when your Briggs and Stratton lawn mower won’t start is the fuel level and quality. Make sure the tank is filled with fresh, clean gasoline. If the fuel has been sitting in the tank for a long time, it may be stale and could clog the fuel system. Drain the old fuel and replace it with fresh gasoline. When this happens, air won’t be able to pass into the carburetor. This prevents the downward movement of gas and will cause your lawnmower to stall. To fix this, remove the bowl screw. You can do this by using a ½ inch plug wrench. Be sure to clean the dirt out of the bowl and then out of the screw as well. Oct 17, 2017. #1. I have a snapper 21" self propelled mower. It has the Briggs 190cc engine. After of about 1 year of using it,for the past couple of months it is having a hard time starting. It used to start on the first pull every time,whether if the engine was hot or cold. It now takes approx 3 -7 pulls before it will start. Step 1- Take the mower Hood off and inspect further: First, you need to take your lawn mower hood off for better access. Then, if you have headlights on your lawn mower, unplug the wiring harness plug. Now, grab the hood, tilted back a little bit, and lift the hood out of the way. Next, you can see the throttle cable in a bracket there. Jun 4, 2017 / Briggs and Statton 12.5 Engine Won't Start but Does Backfire. #2. First thing is a new plug, buy a few. Depending upon the gas you are getting where you are, some times when a pug gets wet that's the end of the plug . The fuel is conductive at combustion pressures and the spark runs down the side of the insulator. Before the engine cools, your engine won’t restart. The plastic covers can also collect dirt and debris and lead to a shutdown of your machine. Wait until your mower engine is excellent; check and clean the plastic housing and the cooling fins on your motor to fix the issue. ( Read How to Sharpen Lawnmower Blades) So, why won't your riding mower turn over? I'll show you how to first diagnose this common Briggs & Stratton Intek camshaft decompression (also called compre Steps to Troubleshoot and Fix the Problem. Now let’s explore the steps to troubleshoot and fix a Briggs and Stratton engine that won’t stay running. Step 1: Check the air filter The first step is to check the air filter. Remove the air filter cover and check if the air filter is dirty or clogged. If it is, clean it or replace it with a new one. F8tQe7.