346xp primer bulb

[forest tink]

ok I have a 346 with a primer bulb on it,it was playing up a bit in a struggling for fuel type of way,i noticed the bulb doesn't pull the fuel through when primed,iv had a wee look and theres no noticeable leak so I was wondering if there could be a diaphragm problem in the carb,any suggestions ?

[forest tink]

meant to say,the saw does run and runs very well till it starts hunting for fuel,then I purge it and nothing comes into the bulb

[wisecobandit]

Theres a 1 way valve in the purge valve which sounds a bit like its failed. (hence 2 different length tails for the pipes to ensure its fitted the correct way around.

 

The other possibility is the fuel pipe has a hole in it somewhere. (usually at the point where it exits the tank)

 

Either would lead to the bulb not priming fully

[forest tink]

ok cheers,i plan stripping down tomorrow night to have a see,funny thing is,sometimes it primes other times it doesn't,tried it with the lid off incase I was jamming the fuel pipe but it made no difference

[wisecobandit]

Maybe a speck of dirt holding the 1 way valve open possibly.

 

It may also be a blockage in the filter gauze inside the carb that blocks sometimes the harder it pulls fuel thru (under load etc)

 

The primer bulb is actually after the carb so to speak. Fuel goes from the tank thru the carb and then thru the primer and returned to the tank. (most ppl are under the illusion the bulb is between tank and carb) Priming the bulb pulls fuel thru the carb so the carbs full before you start it, back thru the primer to the tank.

A hole in the fuel line simply pulls air into the system hence not filling the carb properly etc OR it can be a intermittent blocked gauze/mesh in the carb.

If it where totally choked chances are the bulb would "stay in" and not refill.

 

The longer tail on the primer bulb should be the return line to the tank.

 

Hope that makes sense but the better understanding of how it works will give you a better idea of your problem

Edited March 12, 2015 by wisecobandit

[forest tink]

think I got it lol,hopefully it an easily found problem

[peatff]

ok I have a 346 with a primer bulb on it,it was playing up a bit in a struggling for fuel type of way,i noticed the bulb doesn't pull the fuel through when primed,

 

How can you tell it's not pulling fuel through ? The bulb always has some air in it but it doesn't mean it isn't working.

[Stubby]

How can you tell it's not pulling fuel through ? The bulb always has some air in it but it doesn't mean it isn't working.

 

You feel the resistance of the fuel being pumped . When its not working its much easier to press in .

[forest tink]

well theres nothing in it,i pump it and theres still nothing in it if you get me,sometimes you pump it,it fills up,i can see the diaphragm on the carb through the wee hole going up and down when its pumped but no fuel comes through

[adw]

This is not a primer, it is a purge, it pulls fuel from the varb, into the bulb, and pushes back to tank, if the bulb pushes in but is very slow to come out, then there is a blockage in the fuel system, always check easy stuff first, fuel tank filter, if ok, dirt in the carb screen under the pump cover, there is two conections on the bulb, short connection is suction so goes to the carb, longer connection is the pressure side so goes back to tank, it is very importent you do not accidently conect the return to tank pipe to the white breather, if the tank has been replaced the conection on the tank is sealed so as to use the tank on a non purge 346, so you need to cut the end of to allow fuel to flow back into the tank.