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John B
John B, Small Engine Technician
Category: Small Engine
Satisfied Customers: 3
Experience:  20 years working with small engines and related equipment.
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how can i fix my lawnmower which is a 3.5 briggs and stratton

Customer Question

how can i fix my lawnmower which is a 3.5 briggs and stratton .i already put a new diaphragm on and it worked one day fora a short time. I think the problem is that i used old petrol. and the usual service is not working.. can you help?
Submitted: 4 years ago.
Category: Small Engine
Expert:  John B replied 4 years ago.

John B :

Hello, and thanks for the question. In order to troubleshoot the machine, we need to think of the 3 basics that the engine needs to run. Fuel, compression, and ignition. Now, assuming the compression is fine since you had it running just recently and you say it died due to poor quality fuel, I would first check the fuel system. You can start by trying to put a squirt of fuel down the carb and see if it will fire, if so, you most likely have a gummed up carb from the bad fuel. If it doesn't attempt to start, you most likely have a fouled spark plug, which could also be a result of the bad fuel. Pull the spark plug to see if it is wet, if it is, the simplest route would be just replacing it. You can also test for spark by holding the plug against the head of the engine, cautiously holding by the rubber boot while you have an assistant spin the engine over. You should see and hear the spark, if it is not blue, it may be too weak to fire under compression. In that case, replace and try again. Please let me know what your findings are when you have a chance, if you need more assistance. Good luck!

John B :

Just to be clear, if you decide to check the spark as mentioned, holding the spark plug boot and being sure not to be near the electrode of the plug, or you could receive a high voltage shock. If you are not familiar with the procedure, I wouldn't recommend it.

John B :

Have you had a chance to try anything that I suggested? Judging by your description, I am pretty sure that you have a fouled plug. Please advise to the results, so we can troubleshoot further. Thanks.

Expert:  John B replied 4 years ago.

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