Primer bulb sticks

Charles in Aus.

Well-known Member
This has happened to a few small two stroke engines I have ; a Homelight leaf blower and a Ryobi trimmer , when pushing the primer bulb down before starting the engine it sticks and won't come up again after the first push . A vacuum is holding it down and no fuel is pumped into the carb .
After some minutes it will rise again but has no fuel in it and will still not pump to the carb . The fuel lines are clear and not kinked and the fuel filter at the ends of the pickup lines are clear as well. I have even removed the filter to prove this .
If I loosen the flange holding the bulb down then air will enter and the bulb will rise but again no fuel is pumped .
Any ideas please on just what part of the carb is causing this ? ,
 

Something is restricting the primer bulbs ability to suck fuel, likely the fuel filter. And, the bulb can get old and not be up to snuff. That's where I'd start.
 
Zama carbs have a check valve in the black base that the bulb sits on that can stick and cause that.
May be cheaper to replace carb
 
I wish they would do away with those things and go back to chokes. I just got a new Husqvarna lawn tractor and I was thrilled to see a manual choke on it.

Primer bulb has a different purpose on a 2 stroke engine than the ones on 4 stroke engines like a lawn tractor uses.
 
There is a stuck check valve or plugged port on the fuel in circuit.

Sometimes with enough blasting with carb spray and air it will free up, sometimes it wont.

I fixed one the other day, drove the check valve out with a small pin, ruined the disc, but made a new one from brass shim stock.

A lot of work, but was able to save it.

Depends on how it's made, some are in places that are not practical to access. In that case best to just replace it with an Ebay carb.
 
Hello Charles in AUS,

Here is a picture for you. Take the fuel line coming from the
carburetor and going to the bulb. Pushing the primer will
tell you whether is the bulb or the carb. This type you
replace just the bulb check valve is in it. The primer that is on the carb has the check valve in the carb part,

Guido.
a267455.jpg
 
Thanks everyone , I suspected that it would be something in the bowels of the carburettor .
Could I use a little compressed air though the lines to try and dislodge the valve or do I run the risk of rupturing a diaphram ?
 
Hello Charles in AUS,

Test pressures for most tests is 10#. Pump diaphragm won't take more the that.
You should take the carb apart. Bet you will find a clogged fuel screen,

Guido.
 
(quoted from post at 16:04:34 05/11/18) Hello Charles in AUS,

Test pressures for most tests is 10#. Pump diaphragm won't take more the that.
You should take the carb apart. Bet you will find a clogged fuel screen,

Guido.

+1

And to add.. Be very careful when taking it/them apart for some have a very small steel ball that acts as a check valve/ball. Lose it and you will need a new carb.

I take them apart on a sheet of white poster board now days just for that reason.. Even if I know the carb does not have a ball in it.
 


Guido gets the cigar :D

blocked fuel screens in the carburettors , a ten minute job on a sheet of white paper like Mulemeat suggested .
Thanks all .

:D
 
Hello Charles in AUS,

This long distance guessing is fun! I prefer a glass of 🍷,

GUIDO.
 
A cookie sheet works best to contain balls and springs flying out. Even better is a clear plastic bag to do the teardown, put it in there when you crack it open.
 

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