Primer bulb question

[Ricko]

Hi, I've just been tinkering with a McCulloch 838 and noticed than when I pump the primer the bulb doesn't fill with fuel and it seems to pressurise the tank causing the fuel to 'splutter' out of the vent in the middle of the filler cap. I presume this means the primer ain't working correctly? Are they easy to get hold of?

Cheers

[peatff]

Lots on ebay, make sure you fit it the right way round as they are directional and pull fuel through the carb.

[GardenKit]

If the primer is pressurising the tank then it is working OK in so much as its pulling air in one side and pumping it out the other, causing air pressure to enter the tank. Normally though, the system does not pressurise the tank as it pulls fuel  from the tank, through the carb and back into the tank, maintaining equilibrium.

So you need to find out why the vacuum from the pump cannot pull the fuel, I suspect the pickup hose is kinked or trapped, or the filter is choked. This would prevent the fuel leaving the tank and also prevent the tank  from venting pressure.

But if this were the only issue the pump bulb would stick down once pressed and not return, so I would check for a fractured hose between the carb and primer.

Edited April 5, 2018 by GardenKit