Primer bulb conundrum

JBtoro

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I am posting at the Echo forum because my current issue involves an ES210 blower vac. Carb is a Zama C1U-K78. But I have had this issue with other equipment brands and carbs as well from time to time. This ES210 is frequently harder to start because I don't use it very often. Noticed that the primer bulb (no cracks) is not filling when being pushed & released. Took it off the unit and placed two fuel test lines on it with the open end submerged in a container of 50:1. Suddenly, with pumping action the bulb filled as it should and bubbles squirted out the exit line. Thus, one would presume that the bulb & check valve operation was working. Then put it back on the ES-210 and ... nothing. Anyone one else experienced this mysterious behavior?

PS - I can get it to start & run great with a shot of carb cleaner in the spark plug hole. Therefore , in run mode the carb is pulling gas as it should.
 

AnthemBassMan

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I’d say either the fuel filter is plugged, or the gas cap isn’t venting and causing a vacuum. Try priming it with either the gas cap loosened or completely off.

L8R,
Matt
 

bertsmobile1

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There is a filter inside the carb itself that can get clogged.
The primer does not pump fuel into the carb, it draws AIR out and pumps that expelled air back into the fuel tank.
When all of the air is gone the primer starts to pump fuel.
Unlile on a mower where the primer floods the carb on a hand held it PURGES air out of the system so the carb's inbuilt fuel pump can work.
The fuel pumps can not pump air.
After a couple of pulls the fuel tank pressurises and normal fuel pumping can occur.
Some carbs have a check valve in the carb, some have a few while others rely upon the duck bill valve in the primer.

When not used for a long time the check valves can get gummed up and the filter in the tank can break down allowing fibres into the carb which blocks the internal filter.
The float valve ( called a metering chamber valve ) is vitton tipped thus very prone to sticking in the closed position .

When you have finished with the equipment it is always a good idea to tip the fuel out and then run the carb dry.
 

JBtoro

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Thanks.Thought about the filter, but as I said, it runs fine if it is "kick started" with a shot of carb cleaner down the plug hole. So that would rule out a clogged filter. As far as venting through the cap, this model has Echo's style of a vent tube trough the grommet for purposes of venting the tank. So, the question remains: why does the purge system work in test mode when removed from the blower but fails to do so when bolted to the blower?
 

JBtoro

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There is a filter inside the carb itself that can get clogged.
The primer does not pump fuel into the carb, it draws AIR out and pumps that expelled air back into the fuel tank.
When all of the air is gone the primer starts to pump fuel.
Unlile on a mower where the primer floods the carb on a hand held it PURGES air out of the system so the carb's inbuilt fuel pump can work.
The fuel pumps can not pump air.
After a couple of pulls the fuel tank pressurises and normal fuel pumping can occur.
Some carbs have a check valve in the carb, some have a few while others rely upon the duck bill valve in the primer.

When not used for a long time the check valves can get gummed up and the filter in the tank can break down allowing fibres into the carb which blocks the internal filter.
The float valve ( called a metering chamber valve ) is vitton tipped thus very prone to sticking in the closed position .

When you have finished with the equipment it is always a good idea to tip the fuel out and then run the carb dry.

Thanks. I am aware of how the purge system works. My question is not about how it works ... but why does it work correctly when removed from the blower in a test mode but fails when the carb is bolted to the blower?
 

bertsmobile1

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Thanks. I am aware of how the purge system works. My question is not about how it works ... but why does it work correctly when removed from the blower in a test mode but fails when the carb is bolted to the blower?

Because in your test mode there is no carburettor between it and the fuel tank
Your carb can be leaking air
If you understood how the system works is should be blatiently obvious.
If the purge bulb does not return when depressed then the fuel delivery channel through the carb is blocked.
If the purge valve does pop back up but the carb does not purge there is an air leak or the valve in the primer is not working properly

And if you understood the system you would know that they need to be pressure & vacuum tested in order to get a meaning full result.
If you don't have a pump, you can do it with nothing more than the primer bulb, it just takes a lot of pumping.
As you understand how it works then it should be easy for you to do a leak test using a jar full of water & the primer.
 
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