# Echo HC-151 trimmer will not start



## pls1014 (Jul 30, 2011)

Hi,

I have an Echo HC-151 gas trimmer that will not start. I have put on a spare (new) carb, I have replaced the spark plug, I have verified the spark plug gives a spark when turning the motor. Also I have verified fuel is going in. I removed the exhaust to make sure the spark arester is not clogged.

The damn thing still will not start. I have taken apart the motor, looked at the cylinder, piston and piston ring. I can not see anything obvious. 
Based on what I have done, I think there might not be compression in the cylinder.

What am I missing? Any ideas?

Thanks
Pavel


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## usmcgrunt (Sep 16, 2007)

Hello and Welcome.Since you have tried some of the obvious repairs,now you will have to confirm that you do have enough compression.The piston creates a vacuum on the down stroke that pulls in the gas mixture and sends it up an internal transfer port to the combustion chamber for ignition.If compression is less than 90 to 100 psi,the engine will not run,OR,run poorly.Did you see any scoring on the piston or cylinder walls when disassembled?Could the piston ring be stuck on the piston?Hope this helps.


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## pls1014 (Jul 30, 2011)

Thanks for your help. No, I have not seen anything on the cylinder or piston walls. The piston ring does not seem to be stuck to the piston. 

To check the compression or vacuum (in down-stroke), I am probably out of luck if I do not have any professional tool, right?

Thanks anyway for the description of the operation of the down-stroke. I could not figure out how it gets the fuel/air mixture in, since I noticed that even at the lowest down position, the piston's top did not reach down enough to create a direct opening into the intake hole. It is probably some internal port that guides the mixture above the piston. 

Is it possible that actually the cylinder does not have enough vacuum to pull the fuel mixture in?

Thanks Pavel


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## usmcgrunt (Sep 16, 2007)

Vacuum and compression are directly related on two cycle motors.If you don't have a vacuum gauge,a lot of auto parts stores will let you borrow one by leaving a deposit.You can buy a cheap one for about $15 and will help diagnose future engine problems since they come with adapters for different spark plug holes.Strong compression/vacuum on a two cycle motor is critical to it's operation.


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## bob1190 (Apr 18, 2010)

Compression check necessary. Also vacuum and pressure check of crankcase.


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## pls1014 (Jul 30, 2011)

Thanks guys for all your advice. I will give it a shot. Pavel


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## usmcgrunt (Sep 16, 2007)

In error and having fingers that type faster than the brain thinks,I told you about borrowing a vacuum gauge.WRONG - I meant to say a COMPRESSION gauge.Sorry!


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