Author Topic: Stihl ts400 won't start  (Read 410 times)

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Offline Davidneilb

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Stihl ts400 won't start
« on: October 15, 2014, 04:15:03 pm »
Hi all,

I have a ts400 that has had service kit including spark plug and all filters.. It was working all be it sometimes took a while to get going,
Then one day wouldn't start, didn't seem to want to catch which led me to think fuel filter.

I have dismantled, installed service parts and blown down all fuel lines etc (even took top & bottom off carburettor and checked that...

My problem is having taken spark plug out and turned it over with pull cord, piston top appears completely dry but I cannot are any blocked lines??

If you put a small amount of fuel in plug hole then put plug back and try to start... It starts perfectly but doesn't continue to run? I know this symbolises fuel delivery I just cannot see where the problem is - any help massively appreciated!!

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Offline 660magnum

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Re: Stihl ts400 won't start
« Reply #1 on: October 15, 2014, 04:20:33 pm »
Look at the check valve tabs on the fuel pump side of the carb that one is not curled up and not sealing?

On the regulator side of the carb, push on the center of the diaphragm to make sure the needle is not stuck in the seat.

Back flush the fuel line to make sure the filter is not plugged.
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Offline Davidneilb

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Re: Stihl ts400 won't start
« Reply #2 on: October 16, 2014, 03:54:38 am »
Hi... thanks for the quick reply and stuff to try!

unfortunately... i have tried them and all seems fine with check valves and seating is fine... fuel filter isn't plugged either.

very frustrating!

Offline jmester

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Re: Stihl ts400 won't start
« Reply #3 on: October 16, 2014, 08:39:51 am »
I would check your impulse line to make sure it is not leaking. Plus I would rebuild the carb. I just rebuilt a carb on a 460 that I did 3 years ago. The metering diapgham was stiff and the needle had a groove wore around where it comes in contact with the seat. So if you have not rebuilt the carb in the past 1 year I would start there. Also take a look at your tank vent to make sure it is working.
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Offline Davidneilb

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Re: Stihl ts400 won't start
« Reply #4 on: October 16, 2014, 09:03:05 am »
thanks Jmester - i have looked at buying a new carb tbh they are only 25 quid or so. will it come pre-set would you think?

how exactly does the tank vent work - i have blown through it whilst off and it doesnt seem to do a right lot?

Offline 660magnum

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Re: Stihl ts400 won't start
« Reply #5 on: October 16, 2014, 09:28:09 am »
Generally, the new carbs from Stihl run pretty good out of the box without adjustment.
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Offline jmester

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Re: Stihl ts400 won't start
« Reply #6 on: October 16, 2014, 11:48:24 am »
New carbs are preset pretty close as mentioned above. The tank vent is there so the internal pressure in the tank can be released as to not vapor lock the tank. not sure what 25 quid is some form of money?
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Offline Davidneilb

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Re: Stihl ts400 won't start
« Reply #7 on: October 16, 2014, 11:57:11 am »
yeh i get the principle of the tank vent, i just wasnt sure of understanding whether it was working accuratley or not? - should it be easy to blow through from either side?

Offline jmester

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Re: Stihl ts400 won't start
« Reply #8 on: October 16, 2014, 12:23:02 pm »
It should be one way. Let the vapor out of the tank. You should be able to suck on the vent and pull air through and not be able to blow it out. The vent should not build any vacuum. If you read it before I changed it I am sorry had it backwards.
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Offline 660magnum

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Re: Stihl ts400 won't start
« Reply #9 on: October 16, 2014, 02:07:50 pm »
I re-made the vent on my oldest Stihl 025 back in July or August and the vent assembly is merely a restriction in the line. Air can go either way inside of it. Fuel has a harder time. The vent was made with a set screw threaded inside a piece of Tygon fuel line.

Some vents amount to having the same material inside as a fuel filter. The newer Stihl MS250 is made this way.

Other vents are a check valve like a "duck bill" one way valve that lets air inside the tank but fuel or vapors cannot get out.
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
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