what the hell have I done wrong

[jayartibee]

Hi gents - I arrive here bearing a problem - not gifts, sorry

Never done much to my MS230C saw before - but I had to replace the purge bulb and then the main fuel line.

The saw ran between the two jobs but after doing the fuel line (which needed carb removal) when I pump the purge bulb, fuel floods the carb. That is not right is it? I can see it squirting into the carb throat if I take off the air intake.

Can anyone help?

 

[ILENGINE]

I would say you have reversed the lines on the primer. If you push fuel into the carb from the primer it will cause the symptoms you are having.

 

[jayartibee]

I'm sure the bulb is connected correctly - it pumps fuel down into the tank and draws it up through the carb.
I also note that, with the purge bulb connected up, pressure builds up in the fuel tank and fuel squirt out as soon as the fuel line is taken off the carb.

 

[jayartibee]

I think the new bulb is faulty - whilst it pushes fuel mainly in the right direction, for part of the pump 'cycle' is's pushing fuel back down the wrong way. Serves me right for buying a non-Stihl one...

 

[StarTech]

If the primer is reverse flowing then yes it is bad. It has two check valves and the in one is not sealing. The primer bulb is a standard Walbro 188-512-1. You don't have buy Stihl if you buy the Walbro you will be fine. Just watch for clones through.

 

[jayartibee]

If the primer is reverse flowing then yes it is bad. It has two check valves and the in one is not sealing. The primer bulb is a standard Walbro 188-512-1. You don't have buy Stihl if you buy the Walbro you will be fine. Just watch for clones through.

the market is flooded (ha ha) with clones - they have a red circle visible in the bulb

got the saw started by using the primer ONCE - any more and the carb is full of petrol!

 

[PTmowerMech]

Correct me if I'm wrong, but the primer doesn't actually put fuel into the venturi, does it? Doesn't it just sort of push all the air out of the carb, back into the fuel tank?

 

[jp1961]

Hello,

Echo (on chainsaws at least) doesn't refer to it as a primer bulb, it's know as a purge valve, I'm guessing it purges air from the carb, totally different than a float type carb, where it does force gas into the venturi.

Regards

Jeff

 

[jayartibee]

you're right about its function. It doesn't fill the carb with fuel (mine does coz it sort of backfires)

It's misleading that Stihl on its parts diagrams calls it a 'Fuel Pump'.

 

[jp1961]

Hello,

I'm no expert on diaphragm type carbs, but the main theory is they use a flexible rubber membrane that is "powered" by crankcase pulses (both pressure and vacuum), to pump fuel into the carb where is is metered in the appropriate amounts. It's possible your carb may need rebuilding, rather than just blaming the purge valve?

Regards

Jeff