b/s vanguard engine

12 years ago

HI EVERYONE. I HAVE A B/S VANGUARD 18HP ENGINE WITH A RUN PROBLEM, WHAT IS HAPPENING IS WHEN YOU START IT UP IT RUNS OK, BUT WHEN YOU SHUT IT OFF THE CYLINDERS FILL UP WITH GAS. I REMOVED THE SPARK PLUGS AND TURNED IT OVER TO CLEAR THE CYLINDERS. I REMOVED THE AIR CLEANER AND RESTARTED THE ENGINE, IT WOULD RUN 30 SEC AND THEN STOP I WOULD SEE THAT WHEN IT STOPPED A LOT OF FUEL WOULD ENTER THE CARBURETOR THROUGH THE BREATHER TUBE. I REPLACED THE CARBURETOR (NEW) AND THE SAME THING HAPPENED AGAIN. THE FUEL TANK WAS CLEANED THE FUEL FILTER WAS CHANGED, FRESH GAS WAS PUT IN. THE COMPRESSION ON THE CYLINDERS WAS 135-128. WHAT CAN BE CAUSING THIS TO HAPPEN.

Comments (3)

bluemower
12 years ago
please post the engine numbers.
Check the engine oil level. The crankcase may be full of fuel and further operation will damage the engine.

Fuel can enter the crankcase from a leaking carburetor or a failed fuel pump diaphram. Since you replaced the carburetor, the fuel pump is a likely source of the crankcase fuel. The fuel pump contains a spring that pushes a diaphram in one direction. Vacuum pulses pull the diaphram the opposite direction. This action draws fuel from the fuel tank to the carburetor. If the diaphram develops a leak, the fuel is drawn into the valve cover and then into the crankcase.

If this is the case, the fuel pump is easy to change. Make a drawing of the hose connections. This is also a good time to replace the fuel hoses that may have deteriorated. The air filter may be soaked with some oil and fuel. Change the oil and oil filter.
rcbe
12 years ago
Also, if your tractor's fuel tank is located above the engine (gravity feed), strongly suggest you install an inline fuel cut-off valve and use it to prevent raw fuel in oil again. Install it ahead of the fuel pump.
Such is serious threat for engine damage - DO NOT run engine until crankcase oil/&filter has been drained/replaced. The raw fuel will cause the crankcase oil to lose it's lubricity in turn allowing rapid engine damage when running.
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rcmoser
12 years ago
that Vanguard probably has the fuel pump (round looking disk usually on the left side of the engine viewing from rear, some are metal and some are plastic, probably get plastic replacement) As suggested by bluemower diaphramn probably leaking (Sphioning) fuel from the gas tank down the vacuum hose that attached to the cylinder head (the third short hose going behind the valve cover). I dought a new carb. needle and seat is bad alowing fuel to run into the cylinders visa the intake manifold, but can't rule it out even though very small chance of it being the problem. rcbe suggest also good one to relieve pressure from the tank when not in use by blocking static (gravity) fuel pressure from the tank.