Brigs & Straton 6.74 hp not starting

[tsgtwheeler]

I have a eco walk behind trimmer. It has a Brigs & straton 6.75 hp. model 799875. I ran it for a while and ran out of gas. I went in and ate some lunch. When I came back out and put in fresh fuel it will not start, but it seems to back fire out of the muffler. I have pulled the carb off and cleaned it with my ultra sonic cleaner. ( I use simple green in my cleaner). I dried the card and blew out all the passage ways. I also tool the flywheel off and the key is not sheared. I did a compression test and am getting about 95 psi in the cylinder. I have installed a new air filter and plug. I do not understand what could be going on. Any help would be appreciated.
Thanks

 

[Oddjob]

Since no knowledgeable person is responding, looks like you are stuck with me. Is this Briggs equipped with their auto-choke? If so, has the thermostatic switch gotten stuck with the choke open after you ran it out of gas? Taryl Fixes All has a good video on this choke. Google it. Stuck open choke might explain popping through muffler. Another possibility is a bad ignition coil. In my experience, a failing coil will work when cool but when you try to restart the coil fails. If you have a spark tester, check it. Or, spray starter fluid through the air cleaner into the carb and see if it starts. If it does not fire, good chance you have no spark. Since you replaced the plug, that leaves the coil as the culprit. Good luck. Maybe someone smarter will chime in. Also, does it have a fuel filter? Maybe there was crud in the bottom of the tank and when you ran it dry the crud clogged the filter.

 

[bertsmobile1]

Remove the rocker cover and check that both valves go in & out the SAME amount
The valves & springs are the same so they sit at the same heights .
If not a valve is stuck
An exhaust valve that is not fully closing or opening way too early will cause a backfire out the muffler .

 

[sgkent]

One thing you might consider is did you actually run out of gas, or was it low and you THOUGHT you ran out of gas? If you are sure you ran out of gas, sometimes it takes a few minutes for the fuel to fill the bowl. If I run my edger out of gas intentionally, then it won't start for 2 or 3 minutes after I put fresh gas in and open the valve.

As a rule of thumb, before pulling anything apart, figure out what is missing - fuel, spark, or compression. Fuel you can squirt a teaspoon into the carb with the air cleaner off. Spark you can use a spark tester or pull the plug, for compression you can hear it if electric start or feel it if it is rope pull. You can also put your thumb on (not in) the spark plug hole. If it is flooded, pull the spark plug and pull it thru a couple times then put the plug back in. Once you know why it doesn't run then take things apart. If you dive right in the original problem may end up compounded. Also, a good friend had an engine that would not start. His dad handed him a gallon of clear kerosene instead of gasoline. He didn't figure it out for about 4 hours of could it be this, could it be that?

 

[DaveTN]

One thing you might consider is did you actually run out of gas, or was it low and you THOUGHT you ran out of gas? If you are sure you ran out of gas, sometimes it takes a few minutes for the fuel to fill the bowl. If I run my edger out of gas intentionally, then it won't start for 2 or 3 minutes after I put fresh gas in and open the valve.

As a rule of thumb, before pulling anything apart, figure out what is missing - fuel, spark, or compression. Fuel you can squirt a teaspoon into the carb with the air cleaner off. Spark you can use a spark tester or pull the plug, for compression you can hear it if electric start or feel it if it is rope pull. You can also put your thumb on (not in) the spark plug hole. If it is flooded, pull the spark plug and pull it thru a couple times then put the plug back in. Once you know why it doesn't run then take things apart. If you dive right in the original problem may end up compounded. Also, a good friend had an engine that would not start. His dad handed him a gallon of clear kerosene instead of gasoline. He didn't figure it out for about 4 hours of could it be this, could it be that?

Good Point on the kerosene instead of gas! There were some friends living up in the far North of Alaska and one of them got a Snowmobile and got it running which extended his range. One night he and a pal got on the thing and the pal grabbed what he "thought" was 2cycle gasoline but it too was kerosene. Well they were about 20 miles out on a frozen lake on a sub-freezing night when they poured the kerosene into the Snowmobile and they had to start walking 20 miles back. Fortunately their friends had realized the situation and took the Snow Cat out and dragged their tied butts back home along with the Snowmobile! So a situation can become lethal in a tight spot like that!