8-20-22

Most of the time the problem of engine not starting can be traced to a bad glow plug, low battery for the glow plug (1½ volts) or bad fuel... but if you checked those items, or you can't get fuel to draw unless you put your finger over the venturi, you may have another problem.

Check the orientation of the spray bar. The spray bar has a small outlet hole to atomize the fuel. This small hole must be pointed straight down into the venturi. If it is pointed to the side or you can see it looking into the venturi, it will not draw fuel. Note: Some Fox engines had 2 hole and must be orientate side to side. Not a good design.

A 2 stroke engine requires a good seal in the crankcase to run properly. As the piston goes up a fuel/air mixture is drawn from the venturi into the crankcase, usually through a port on the crankshaft on most model glow engines. As the piston goes down the port closes and fuel/air mixture is compressed in the crankcase. This is called base compression. When the piston nears the bottom of the stroke the exhaust ports open in the cylinder then the cylinders inlet ports open, the fuel/air mixture is blown into the cylinder clearing the remaining exhaust and supplying the new mixture for combustion.

If there is a leak in the crankcase, the engine may not start or draw fuel. If you have a leak, as the piston goes up it will not draw sufficient air through the carburetor to create fuel draw. If it is a small leak you may get the engine started but it may run erratically at higher RPM's.

You can check your base compression by removing the glow plug and turning the engine over in the correct direction. You should feel slight compression as the piston goes down and hear a "puff" sound as the ports open in the cylinder. If you don't, try to determine where the leak is.

If you are using a crankcase pressure tap, be sure the line to the tank is good and the tank is not vented. Plug off the nipple off while checking base compression.