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Chainsaw primers/ re fitting hoses

It is quite obvious, by the amount of reqests we see that there is confusion regarding the correct orientation of fuel hoses on externall primers.
Lets start by saying this component is not a primer, if you were to push fuel into the carb, you would just flood it, and make starting near impossible, they are purges, they actually pull fuel from the carb, and dump it back into the tank, this way you cannot over purge the machine, and when the saw runs out of fuel, it very quickly re fills the carb ready for easy re starting.
So the fuel hose from the fuel tank,the one with the fuel filter on the end, goes to the fuel inlet elbow on the carb, this is the elbow closest to the pump cover on the carb, normally held with one philips head screw and made of alluminium. The other hose from the carb, closest to the metering side of the carb, normally held with four screws and made of chrome plated steele, goes to the shorter of the two connections on the back of the purge, this is the suction side,by pulling fuel from the carb emptys the fuel chamber, atmospheric pressure from the vent hole in the metering cover pushes the metering diaphram down opening the fuel inlet needle, allowing fuel from the tank to enter, and re fill the chamber, you can test this by putting a finger over the connection, depress the purge bulb and let go, you should feel your finger sucked down, the longer of the two connections on the back of the purge is the pressure side, this hose will go back to the tank, it will just push into the tank with nothing on the end, you can test this side by putting a finger over the connection, depress the purge bulb, you will feel a pressure on your finger, if you have clear fuel hoses, you will be able to see the fuel movement. Any signs of cracks, splits, or fuel loss from any of the hoses will greatly effect the running and well being of the machine.
I hope this has been helpfull and informative.

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husqvarna 322c

It is possible the clear fuel hoses have become brittle and have cracked allowing leakage and poor running,its just a matter of replacing the hoses, take note of the orientation of the hoses on the carb and primer

May 29, 2013 | Garden

2 Answers

Ryobi Grass Scorpion Petrol lines from tank to primer to carby where to where

Thanks to doityourself.com.

The line off the top of the primer bulb goes to the top of the carburetor.
The line on the bottom of the primer bulb goes to the fitting on the center of the fuel tank and the line off the side of the fuel tank goes to the bottom of the carburetor.


Oct 28, 2008 | Ryobi 15" Electric Factory Reconditioned...

1 Answer

changed primer bulb and now wont run with throttle idles fine

If it has a remote primer you need to make sure you have connected it up the correct orientation, the primers pull fuel from the carm, and dump back to tank, they do not push fuel into the carb, the longer of the two pipes on the back of the primer is the pressure side so goes back to the tank, not the carb.

Aug 26, 2011 | Garden

1 Answer

Fuel is not going up the fuel line to the carb. I

What model blower is it? It should have two or three fuel lines going to the tank. One pulling fuel from the tank, with the filter on the end of it. The second one is a return line from the primer, and the third ,If their is one is the vent line.

Make sure when replacing the fuel lines that you do it one at a time so as not to confuse the pick up and discharge hoses.

The primer, when it has the hoses connected correctly, will have SLIGHT pressure when being depressed. If the hoses are crossed, the primer will be very difficult to push down and will NOT spring back up, it will stay "stuck" down for a few seconds.

Hope this helps.

Nov 04, 2010 | Echo Garden

1 Answer

I am replacing the fuel tank assy and purge bulb (i.e. primer) on my Sears Craftsman model 358.798940. The original plastic tubing was old and brittle and broke apart while disassembling, so I could not tell how the tubing was routed. The new fuel tank comes with two lines -- one fuel supply w/filter, and a second line (probably for fuel return). I presume that I hook these up to the carbuerator (which has two fittings) -- correct? The purge bulb has two fittings for plastic tubing -- where are these routed?

The order of fuel travel should be:
Fuel filter to fuel hose to Carb's Fuel Supply nipple. (On the main body of the carb)
Primer Plate Nipple on carb to fuel hose to Suction Nipple on Primer Bulb. (It must pull fuel thru the carb, not push)
Pressure Nipple on Primer Bulb to fuel hose to Fuel Tank Return hose.

When correctly installed, the fuel will be PRESSED into the fuel tank via the return hose when primer is pressed in . . . and SUCTIONED out of the tank and into the Carburetor when primer in released.

Hope this helps,

Oct 16, 2009 | Garden

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