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String Trimmer only runs with choke on

post #1 of 16
Thread Starter 
Had this problem with it last year so today I figured I'd take a whack at fixing it. It's an echo trimmer with a Zama carb. The unit only starts with choke closed and throttle wide open. Once it's running, it only runs for 10 secs, or so,before it dies. If you try to open the choke it begins to rev a bit but then dies.

Here are the fixes I've tried so far:



1) I drained all the fuel and put new in.

2)Removed carb and cleaned it with carb cleaner and installed new gasket kit (pump diaphragm, etc).

3)New Spark Plug

4)Removed Spark arrestor screen in muffler and cleaned it.



I'm no pro mechanic, but am usually good at fixing things. This one sure has me baffled. I had someone who used to work in a small engine repair facility look at it and he said to rebuild the carb. Since I had already done that I'm hoping that there's someone here that can offer some help. Thanks!



Valentine
post #2 of 16
carb problem, probably a clogged passage.
post #3 of 16
Make sure you dont have a clogged fuel filter or a hole in the fuel line to the carb. But it does sound like you have missed something in the carb blocking a passage.
post #4 of 16
Thread Starter 
I think I cleaned the carb very well and don't believe theres a clogged passage. Thought of the fuel lines too, but they're good. Fuel filter on pickup tube is a possibility. I have not changed it, and I recall that the last time the unit ran, I had to close the choke part way to get proper rpm's.So now I'm thinking that perhaps the filter was clogging and needed the additional vacuum created by the choke to draw fuel. I'll get a new filter and see if that does the trick. Thanks guys.

Valentine
post #5 of 16
Quote:
Originally Posted by valentine View Post
I think I cleaned the carb very well and don't believe theres a clogged passage. Thought of the fuel lines too, but they're good. Fuel filter on pickup tube is a possibility. I have not changed it, and I recall that the last time the unit ran, I had to close the choke part way to get proper rpm's.So now I'm thinking that perhaps the filter was clogging and needed the additional vacuum created by the choke to draw fuel. I'll get a new filter and see if that does the trick. Thanks guys.



Valentine



I you are going to replace the Pickup Filter, change the Fuel Line too. I have been seeing a lot of Lines with Air leaks from tiny cracks lately.
post #6 of 16
Thread Starter 
Quote:
Originally Posted by Wraith View Post
I you are going to replace the Pickup Filter, change the Fuel Line too. I have been seeing a lot of Lines with Air leaks from tiny cracks lately.


Good idea. I know that I already have a few feet left over from another repair, so that'll be easy. Thanks for the suggestion.

Valentine
post #7 of 16
also check to see if the needle is stuck, i had an outboard with a stuck needle and had a similar problem, reset the needle and it was all better
post #8 of 16
Thread Starter 
Quote:
Originally Posted by Jae View Post
also check to see if the needle is stuck, i had an outboard with a stuck needle and had a similar problem, reset the needle and it was all better


Already did that and the needle moves as it's supposed to. I'm betting on the clogged fuel filter nbeing the culprit, now. Thanks.
post #9 of 16
Quote:
Originally Posted by valentine View Post
Already did that and the needle moves as it's supposed to.



Even though the needle may SEEM to work properly, it could still be the culprit.....not so much the needle itself, but the rubber O-ring it seats into. With the ethanol in the gas, those rubber parts tend to swell, and it only takes a bit to screw things up...........I KNOW, as I have had similar issues with other gas engines recently.
post #10 of 16
Thread Starter 
Steve, I don't think there's an O-Ring for the needle. At least I never saw one. I checked the parts schematic and it doesn't show one either. Thanks.



Valentine
post #11 of 16
The needle has a rubber tip and that is the part that will screw up the level of fuel available for the carb to use. Unless you force it by running on parcial choke.
post #12 of 16
Check the vent in the gas cap. They have a habit of clogging.
post #13 of 16
The gas cap is often overlooked but often a major contributing factor. My ice auger had similar issues and sure enough the gas cap fixed it.
post #14 of 16
2 cycle engines are notorious for carbon build up at the exhaust port. Remove the muffler and make sure all is clean. Use only a good quality 2 cycle oil that produces less carbon.



v.
post #15 of 16
Thread Starter 
Here's the latest update on my trimmer woes.

Spent a good part of the day going over what I've already done and then replaced fuel filter and fuel lines. Still no fix for the problem. So, I went and talked to someone I know that used to work in a shop that repaired small engines. He told me that I've either blown one of the motors gaskets or it has a bad or stuck ring. That explains why the motor ran, although poorly, while fully choked; it was still able to draw air into the combustion chamber through the bad seal.It can be fixed and he offered to help me do it, but suggested that I just go out and buy a new machine rather than go through the trouble and expense of such a repair. I think I'll take his advice. So, thanks to all of you for your suggested fixes. Anyone have any recommendations for a new string trimmer ? Thanks.



Valentine
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