From Newsgroup: uk.d-i-y

A friend has asked to look at a nearly new Stihl strimmer that herCOs been given that wonrCOt run.

The fault is fairly obvious as the primer bulb was completely dry and wonrCOt pump the fresh fuel in the tank. It will pump air back into the tank but thatrCOs all.

I manually filled the bulb with some fuel to see if hydraulic pressure
would overcome the blockage but no dice.

https://photos.app.goo.gl/bAwm1tKLyvpAD9hc9

On the underside of that assembly thererCOs something that looks like a very small poppet valve but I canrCOt see any way of freeing it off. IrCOve tried poking a pin down through the small central hole under the priming bulb. Soaking in IPA hasnrCOt done anything either.

https://photos.app.goo.gl/x9yUesg5S21uQ3xC9

Undoubtably itrCOs been left with fuel in it that has dried out but IrCOm wondering if thererCOs any way to free it off (sans ultrasonic cleaner)? IrCOm only thinking that it might come in handy as a spare if I can free it off. IrCOve already lashed out -u10.89 for a replacement carb so whilst my question is a bit academic, I enjoy a challenge. ;-)

Tim
--
Please don't feed the trolls
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From Newsgroup: uk.d-i-y

On 24/02/2026 17:00, Tim+ wrote:

A friend has asked to look at a nearly new Stihl strimmer that herCOs been given that wonrCOt run.

The fault is fairly obvious as the primer bulb was completely dry and wonrCOt pump the fresh fuel in the tank. It will pump air back into the tank but thatrCOs all.

I manually filled the bulb with some fuel to see if hydraulic pressure
would overcome the blockage but no dice.

https://photos.app.goo.gl/bAwm1tKLyvpAD9hc9

On the underside of that assembly thererCOs something that looks like a very small poppet valve but I canrCOt see any way of freeing it off. IrCOve tried poking a pin down through the small central hole under the priming bulb. Soaking in IPA hasnrCOt done anything either.

https://photos.app.goo.gl/x9yUesg5S21uQ3xC9

Undoubtably itrCOs been left with fuel in it that has dried out but IrCOm wondering if thererCOs any way to free it off (sans ultrasonic cleaner)? IrCOm
only thinking that it might come in handy as a spare if I can free it off. IrCOve already lashed out -u10.89 for a replacement carb so whilst my question
is a bit academic, I enjoy a challenge. ;-)

Tim

I would expect something that is intended to prime when used to have
some sort of one-way valve that allows suction from the tank but not
pressure into the tank. The fact that yours is putting air into the
tank indicates that the valve is either leaking or is stuck in the open position.

If you can locate where the valve is on the route from tank to the
poppet, you will find what the problem is. However if the valve is a
flap that is supposed to move but is stuck and you have punctured the
flap with your pin, you probably won't be able to fix it now.

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From Newsgroup: uk.d-i-y

Indy Jess John <bathwatchdog@OMITTHISgooglemail.com> wrote:

On 24/02/2026 17:00, Tim+ wrote:

A friend has asked to look at a nearly new Stihl strimmer that herCOs been >> given that wonrCOt run.

The fault is fairly obvious as the primer bulb was completely dry and wonrCOt
pump the fresh fuel in the tank. It will pump air back into the tank but
thatrCOs all.

I manually filled the bulb with some fuel to see if hydraulic pressure
would overcome the blockage but no dice.

https://photos.app.goo.gl/bAwm1tKLyvpAD9hc9

On the underside of that assembly thererCOs something that looks like a very >> small poppet valve but I canrCOt see any way of freeing it off. IrCOve tried
poking a pin down through the small central hole under the priming bulb.
Soaking in IPA hasnrCOt done anything either.

https://photos.app.goo.gl/x9yUesg5S21uQ3xC9

Undoubtably itrCOs been left with fuel in it that has dried out but IrCOm
wondering if thererCOs any way to free it off (sans ultrasonic cleaner)? IrCOm
only thinking that it might come in handy as a spare if I can free it off. >> IrCOve already lashed out -u10.89 for a replacement carb so whilst my question
is a bit academic, I enjoy a challenge. ;-)

Tim

I would expect something that is intended to prime when used to have
some sort of one-way valve that allows suction from the tank but not pressure into the tank. The fact that yours is putting air into the
tank indicates that the valve is either leaking or is stuck in the open position.

If you can locate where the valve is on the route from tank to the
poppet, you will find what the problem is. However if the valve is a
flap that is supposed to move but is stuck and you have punctured the
flap with your pin, you probably won't be able to fix it now.

I must admit to questioning my sanity as to how these things work. ThererCOs one obvious one-way valve that I think only directs fuel back to the tank.
I rather suspect that it should be sucking up fuel through the other
connection to the carb which must be blocked somehow. I think IrCOve misunderstood the normal flow direct of fuel through it.

Tim
--
Please don't feed the trolls
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From Newsgroup: uk.d-i-y

On 25/02/2026 16:56, Tim+ wrote:

I must admit to questioning my sanity as to how these things work. ThererCOs one obvious one-way valve that I think only directs fuel back to the tank.
I rather suspect that it should be sucking up fuel through the other connection to the carb which must be blocked somehow. I think IrCOve misunderstood the normal flow direct of fuel through it.

Tim

Never use a pin or compressed air, just carb cleaner.

The bulb is a purge pump; it pulls fuel through the carb from the tank
(via a drilling beside the check valve usually) and dumps it back into
the tank. This means the carburetor is full of fuel before you pull
start, so it doesn't rely on the induction pulses to prime the carb.
Hence less pulls necessary.
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From Newsgroup: uk.d-i-y

AJH wrote:

On 25/02/2026 16:56, Tim+ wrote:

I must admit to questioning my sanity as to how these things work.
ThererCOs
one obvious one-way valve that I think only directs fuel back to the
tank.
I rather suspect that it should be sucking up fuel through the other
connection to the carb which must be blocked somehow.-a I think IrCOve
misunderstood the normal flow direct of fuel through it.

Tim

Never use a pin or compressed air, just carb cleaner.

The bulb is a purge pump; it pulls fuel through the carb from the tank
(via a drilling beside the check valve usually) and dumps it back into
the tank. This means the carburetor is full of fuel before you pull
start, so it doesn't rely on the induction pulses to prime the carb.
Hence less pulls necessary.

Thank you. That's another unknown unknown ticked-off.
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From Newsgroup: uk.d-i-y

AJH <news@loampitsfarm.co.uk> wrote:

On 25/02/2026 16:56, Tim+ wrote:

I must admit to questioning my sanity as to how these things work. ThererCOs
one obvious one-way valve that I think only directs fuel back to the tank. >> I rather suspect that it should be sucking up fuel through the other
connection to the carb which must be blocked somehow. I think IrCOve
misunderstood the normal flow direct of fuel through it.

Tim

Never use a pin or compressed air, just carb cleaner.

The bulb is a purge pump; it pulls fuel through the carb from the tank
(via a drilling beside the check valve usually) and dumps it back into
the tank.

I worked this out once I got the new carb. ;-)

I dare the that the old carb could have been resurrected with some serious cleaning but with the low cost of replacement and lacking an ultrasonic
cleaner replacement seemed easier. At least IrCOve learned that fuel in the bulb is whatrCOs been sucked through the carb (and is returned to the tank
when you squish it) rather than fuel sucked from the tank on its way to the carb.

Tim
--
Please don't feed the trolls
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