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Outdoor Power Equipment Guru
Category: Small Engine
Satisfied Customers: 540
Experience:  I have worked twenty years as a Mechanic and am a State of Michigan Certified teacher in Small Engine and related equipment.
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Small Engine

Engine wont start & carb is flooding gas

Good Day: Symptom: Engine won't... Show More

Good Day: Symptom: Engine won't start & carb is flooding gas through engine and out exhaust manifold I have a Stihl FS 56 String Trimmer that I'm restoring. (It had been sitting in a shed for 3 years without fuel drained etc...) I've replaced fuel line and am rebuilding Walbro WT 45A Carb. I've replaced diaphragm, fuel pump membrane, gaskets, needle, spring and filter screen. I've popped the pop-out and cleaned the 3 ports with carb cleaner and blown all orifices with air. I soaked the entire carb in cleaner for 30 mins and then wiped and blew all orifices. I reset the needle system with the Walbro Gauge so it just touches gauge. I tested spark - have good, solid, bright spark to plug. To restart, I preset the hi & lo needles to 1 1/2 turns and pulled on cord. After several pulls with no start, I get fuel spray out of exhaust manifold; check plug and it's wet. I'm at a loss as to the problem. Any ideas?


My name is XXXXX XXXXX my e-mail address is [email protected]

Submitted: 5 years ago.
Category: Small Engine
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Jeremy R., Technician
Satisfied Customers: 9019
Experience: 15+ years of experience and a business owner.
replied 5 years ago.
Hi, and thank you for letting me try and assist you with your problem.

well first check for spark
if no spark un plug the on/off switch
test for spark again and let us know
Customer reply replied 5 years ago.
I unplugged the on/off switch - no change. The carburetor is literally flooding the cylinder with gas (fresh mix). The spark plug is wet. I removed the exhaust muffler and dumped a large amount of gas/oil mix out of the exhaust manifold. I used air to 'dry' out the cylinder area. At present, the carburetor has been removed from the cylinder intake manifold. I have cleaned it (several times) and blown air throughout the ports. I've installed new gaskets and pump/diaphragms. I've adjusted the LO and HI needles to 1 1/2 turns. When I attempt to start the trimmer, I get ZERO combustion - not even a hint of trying to start. I've checked the cylinder head and have compression. It appears the carb is literally flooding the engine; although, I don't see any sign of fuel intake needle being bad (it too is new, along with spring). I'm stuck and out of ideas....
Outdoor Power Equipment Guru, Technician
Satisfied Customers: 540
Experience: I have worked twenty years as a Mechanic and am a State of Michigan Certified teacher in Small Engine and related equipment.
replied 5 years ago.
Hi Larry my name is XXXXX XXXXX I may be able to help you with this.

The FS 51 and 56 were built on the same powerhead and were god awful machines when they were brand new. The problem you are describing sounds like your crankcase is full of fuel from previous flooding and probably is not due to your carb being bad at tis time. There are a few ways to deal with this, pull the plug turn the ignition off and put your air nozzle in the plug hole and turn the engine into a pump and pump the crankcase clear it makes a hell of a mess and takes a while. Then drain your fuel and crank it up, run it till it dies refill the fuel and see what happens.

Option two involves a hammer and a dumpster.

Let me know if this helps.