Husqvarna 460 Rancher fuel breather problem

[JohnBoyy]

Long time lurker, finally actually registered because I have a problem I can't figure out.

 

I have a 460 rancher which dies under load once it's been running for a while, crack open the fuel tank and it will run fine for a few minutes then again, rinse and repeat over and over again.

 

I replaced the fuel tank breather with a spurious one and it ran like a champ, but leaked fuel so I plumped for the genuine article and I was back to square one dieing out after a few minutes of any load.

 

it seems I can have leaking fuel or crap running.  

 

Any thoughts as to what could cause this?  Is there a fuel cap from a different model that might fit that would be vented, maybe two breathers might work?  took it to two different saw shops who both could find nothing wrong (I suppose they cant so easy run under load on a workbench)  I figured out the breathing issue myself, but I'm stumped as to where to go now.

 

Any ideas wise people of arbtalk?

[adw]

This breather is used on many different models with no issues, you can do a pressure/ vac test on the breather itself, this what I normally do, this will tell you straight away if the breather is faulty, just maybe it was a bad one, we use it on the 550/560/562 etc and I see vert few problems with them.

[JohnBoyy]

I have a mityvac tester 

Mityvac MV8500 Pressure & Vacuum Tester Pump & Fittings

EUROSMALLENGINEPARTS.IE

---

Mity Vac Pressure & Vacuum Tester Pump & Accessories Checks Carbs, pipes & seals etc 2 in 1 tool for pressure & vacuum testing.   

 

 

what am I looking to see on the gauge?

[Muddy42]

Have you checked the other elements of fuel delivery?  I've found before that another issue could be compounding the problem, that is just marginal enough to be fixable by opening the fuel cap.

 

clogged fuel filter?  Old soggy fuel line or even leaking.  Is the fuel line routed smoothly not kinked? Have you sprayed out the sawdust from the fuel pump end of the carb, removed and cleaned out the jets?

[JohnBoyy]

To be honest I havent done anything specific because the leaky spurious breather left it running fine, One of the services the fuel line and filter were supposed to have been changed to no effect but I will check everything over again

[Muddy42]

2 hours ago, JohnBoyy said:

I have a mityvac tester 

Mityvac MV8500 Pressure & Vacuum Tester Pump & Fittings

EUROSMALLENGINEPARTS.IE

---

Mity Vac Pressure & Vacuum Tester Pump & Accessories Checks Carbs, pipes & seals etc 2 in 1 tool for pressure & vacuum testing.   

 

 

what am I looking to see on the gauge?

 

Try this.

 

Disconnect the whole fuel tank section of the saw.  Clean, empty and dry out the fuel tank and fuel line.  Clean breather valve with toothbrush and/or a pin.  Connect mityvac to the fuel line, which in turn is linked up to the fuel tank in the normal way.  Try pumping small vacuum and pressure.  It should hold very little vacuum the vacuum will vanish immediately and you should hear the breather hissing/sucking in air. The tank should hold more pressure and for longer - to be honest you're looking for leaks rather than an exact number.

[JohnBoyy]

Thanks for the tips folks.  I've to check the fuel filter yet, but everything else looks good, fuel hoses look and feel good, no kinks or anything looking wrong.

 

I've done some playing with the vacuum gauge, started by testing the three breathers I have.

 

The original tank breather is clearly clogged, it holds about 3 inches of vacuum whereas the new genuine drops to zero in a second or two, so it definitely seems blocked  the new spurious one barely registered on the gauge but that's no surprise since the metal element falls out.  (so the first thing I'm wondering is there any chance I reinstalled the original genuine one, but I'm 99% sure I didnt)

 

So I reinstalled the new genuine breather.  I didn't remove the tank, It's not immediately obvious to me that you can on this saw, it looks to me to be part of the chassis.

 

Then I pulled the fuel hose off the carb and pulled vacuum, and no fuel came through.  I had 20 inches of vacuum for a few minutes, even with the tank open.  currently fuel in the tank.

 

If I swap and pull vacuum on the hose from the tank to the primer bulb inlet I can draw a hundred ml of fuel in a half dozen pumps.

 

I'd have expected that I should be able to pull fuel through the primer as that's what the carb has to do to run?

 

I came in to look at the parts diagram on the computer screen and it seems to plumbed right with the tank hose on top and carb on the bottom.

https://www.hsqintec.sk/vykres/h460-mot.-pila.pdf page 22

[JohnBoyy]

I just realised the primer is on the return line, some dope!!!

[Muddy42]

It will be possible to dissasemble the saw in two. Look at youtube videos for help.

 

Have you connected the primer back up the wrong way? We’ve all done it.

 

Presuming you have tested everything and cleaned the breather, maybe the new breather is just defective and needs returning to the seller and replacing?

[adw]

Will everybody stop calling it a bloody primer, it’s a purge!