Stihl 046 Magnum runs out of fuel once warmed up

[Timbco84]

Edit, originally thought this was a fuel level problem, seems to be related to getting proper fueling once the saw is warmed up. See more detailed post below.

Saw runs great for the first 10 minutes or so, then starts starving for fuel/dying. Problem worsens when you tilt the saw around such as limbing, finishing cuts with the tip down etc. Did a full carb adjustment with the H, L, and LA screws and a Tachometer and still no better.

 

[jhall]

Might try replacing the fuel line. Could have a hole/crack in it, causing it to suck air around the halfway mark.

 

[Beer Gut]

Might try replacing the fuel line. Could have a hole/crack in it, causing it to suck air around the halfway mark.

What he said.

 

[1Cut]

Dose the filter have a weight in it or the standard one?

 

[Timbco84]

Dose the filter have a weight in it or the standard one?

Not sure, just got the saw so I haven't had the fuel filter out yet. It does seem awful light just dangling from the fuel line. I also wondered if it might be floating up a bit. Is there a weighted filter available from stihl?

I also wondered about the possibility of a hole/crack in the fuel line, that will be something I will check. Just wondered if this was something common with an easy fix. I know on my 066 the tank is pert near dry when it starts hiccuping low on fuel.

I appreciate the replys.

 

[Beer Gut]

Not sure, just got the saw so I haven't had the fuel filter out yet. It does seem awful light just dangling from the fuel line. I also wondered if it might be floating up a bit. Is there a weighted filter available from stihl?

I also wondered about the possibility of a hole/crack in the fuel line, that will be something I will check. Just wondered if this was something common with an easy fix. I know on my 066 the tank is pert near dry when it starts hiccuping low on fuel.

I appreciate the replys.

Possibly that previous owner put some aftermarket filter on and yes it floats. Might be able to see with the tank like 1/4 full, take the fuel cap off and tilt the saw until gas is at the lip of the tank and see if the filter is bobbing at the surface.

See lots of filter deals on ebay and such. And with ethanol gas cracked fuel lines are common.

 

[Nate66n1]

I replaced a fuel filter on a 026 with an aftermarket and as soon as I would put the saw on its nose when running it would die. Put a factory stihl filter in it and no problems since then. Also I believe the orange filters are weighted.

 

[Timbco84]

I replaced a fuel filter on a 026 with an aftermarket and as soon as I would put the saw on its nose when running it would die. Put a factory stihl filter in it and no problems since then. Also I believe the orange filters are weighted.

Well I stopped and got a weighted stihl filter for it today. The one I removed was a stihl filter, but unweighted. I'll have to wait till this weekend to run it and see if that solves the problem. The fuel line looked free of cracks/holes, and nice and flexible still.

 

[nmurph]

Even the cheap, aftermarket filters are weighted, just not enough.

 

[Timbco84]

Well that didn't fix it. The saw ran perfect till half a tank, then I let off the throttle after a cut and it died. Filled the tank back up to deny/confirm if it was a hole in the fuel line problem and the issue was still present. Runs great till you let off the throttle then tries to die. I can keep it running if I feather the throttle most of the time, then the saw returns to a perfect smooth idle and will rev as normal. Also, once issue is present, if I set the saw down, when I pick it back up, the saw drops rpm and sometimes dies. I feel like it has to be a fuel related issue because it also acts like a saw running out of gas in that it seems to lean out right before it falls on it's face and tries to die. I'm not familiar with carburetors in a saw application, but have a good working knowledge of them in a snowmobile application. Could this be a L adjustment issue?

I would also say to the condition of the saw, the original owner put maybe 10 hours on it, the saw is in show room condition cosmetically. Hard to think a part is worn out. Reminds me of a plugged pilot jet, which since the saw sat around alot obviously, could be possible from gunk built up in the carb. But if I can recover it when falling on it's face it will idle perfect, that and it runs to good for the first 15 minutes, basically till it's as full operating temperature I guess.

If I don't find an answer here directly, I will start a new thread since this obviously isn't a fuel level problem.

Thanks

 

[SilverKing]

weak diaphragm,possibly not able to pull fuel from more than a half tank down?Shot in the dark,but possible,and a cheap try

 

[MustangMike]

If the saw is not new & has low hours it is quite likely a carb problem. If it is just gummed up, it may clear itself, but I may also need a rebuild or cleaning. Wood Doctor has had good results soaking them for 24 hrs in mix. You may want to try it, and I would replace the fuel line even if you can't find a problem with it. Always do the easy stuff first.

Best of luck with it, and keep us posted.

 

[Nate66n1]

Did you give the low speed screw a little tweaking yet?

 

[Timbco84]

Did you give the low speed screw a little tweaking yet?

Well I took the saw fire wood cutting Saturday. Fired it up and started cutting the first tree, ran great for the first 10 minutes or so, then it tried to die on me so I went and grabbed my tachometer and gave it a full tune, after adjusting the Low speed screw ended up back where it was originally, the idle screw also, the saw was only pulling 11,000 rpm full throttle, so I cranked it up to 13,500 where it is supposed to be and went back to cutting wood, problem still present. Finished the tree and let the saw set/heat soak for 15 minutes till we got to the next tree. Started the saw up and learned a lot about the problem

Once completely warmed up, the saw runs "decent" when held level, you start flipping it around to bump knots or tip down to finish a close to ground cut and that's when it really wants to run out of fuel and die. Picking the saw up quickly and it chokes out also. Probably died 12 times limbing the second tree. This really has me stumped since I can use the saw however I want for the first 1o minutes it runs, and then it falls flat on it's face. Definitely a fuel starvation issue, doesn't lean out and grab RPM like an air leak, now that I've had time to study it, it literally is starving itself for fuel. Also messed with cracking the fuel cap to check for vacuum/vent problems, and filled up with fuel, still no change. How can it perform perfect at first... then develop this symptom?

 

[Nate66n1]

I would go get a new stihl fuel line and clean the carb while your at it. Almost sounds like a seal problem but unless you vacuum/pressure test it you won't really know for sure. That is a weird situation you have.

 

[stihl for life]

by any chance have u rebuilt the carb? Yet

 

[Timbco84]

I would go get a new stihl fuel line and clean the carb while your at it. Almost sounds like a seal problem but unless you vacuum/pressure test it you won't really know for sure. That is a weird situation you have.

Well I dove in and took the carb off. Does the fuel line usually have pressure when you remove the carb? I cracked the fuel cap and it blew a little pressure off, then the fuel line continued to spit fuel for a second. Should that tank have pressure like that? Possible the vent isn't working properly? I never heard it take a gulp of air when I opened it after running. but definitelly had internal pressure just now.

 

[Timbco84]

by any chance have u rebuilt the carb? Yet

I have the carb apart now, everything is clean/new looking. The pump and metering diaphrams both look great, not that that means they are working properly, but clean and free of any defects. Jet is clean as I expected. Can a guy put compressed air to the little passage ways under the metering diaphram without hurting anything? just to make sure they are clean and clear.

Thanks

 

[mopar1rules]

Maybe your impulse line has some cracks starting in it, and depending how the saw is tipped, loaded, flexed, etc, it temporarily opens that crack up enough to stop the vacuum applied to the diaphragm in the carb, thus no fuel gets pulled and it dies???.....

 

[stihl for life]

I have the carb apart now, everything is clean/new looking. The pump and metering diaphrams both look great, not that that means they are working properly, but clean and free of any defects. Jet is clean as I expected. Can a guy put compressed air to the little passage ways under the metering diaphram without hurting anything? just to make sure they are clean and clear.

Thanks

is the metering lever flush with the carb