562xp warm start trouble, air purge stops working for a while

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Solrael

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I've got a 562XP which unfortunately doesn't have a warranty. It starts cold beautifully, it restarts hot just fine (slide up to choke on, slide back down to fast idle engaged). After cutting for a while it gets more and more likely that it won't restart, particularly if left for 10 minutes or so, and almost definitely won't start if I leave it for 20 minutes. Once I see that I have a problem, if I leave it alone for a while (never timed it) it comes good again, so it seems to get into some kind of temperature related state. Also, I've not sat down with a stop watch (yet), so my times may be a bit off.

Things that may be relevant..

When it's in this state the air purge bulb doesn't "work", pushing in feels too easy and it never pulls fuel through. I can tell when it's good to go again because I'll come back and the bulb will suddenly be almost completely full and it'll start just fine (though it does idle a bit funny after these restarts, sometimes dies but starts right back up again, but after the first cut it's back to normal).

Oh, the important bit, when it's in this state I can't seem to get it started at all. Sometimes I can get a little rumble for a few seconds but usually nothing.

When you open the fuel cap air there's some positive pressure in the tank. Opening & closing the tank doesn't change anything (I've never had first hand experience with vapour lock, but it seemed like it was worth a test). The weather here's around 15-25C, nothing extreme.

The carburettor is an EL46, no hesitation off idle issues, and from a cold start it's fantastic. Sometimes after a warm restart (or one that's just on the edge of getting it going again) it can be a little reluctant to idle until it gets back up to temperature, and sometimes needs a few blips to get itself sorted out. When I say warm here, if it's running, I stop it to roll a few logs and start it again within a minute or two I'll call it hot, and those starts are fine. Warm would be maybe up to 10 minutes or so, and much more than that I'd be expecting it to get stuck again.

I have been having an ongoing issue with really fine dust getting past the filter. I think it's the crappy bark on these gum trees. I'm pretty confident I'm on top of the problem now that I've got some spray oil for the filter now, and have started running a small line of grease around the outside edge of the filter holder in case it's getting around the filter (I found a thread about that). I took the carburettor off last night and cleaned out some obvious fine dust (that I really hope hasn't done damage to the cylinder), I haven't tried it again yet.

I did come across a comment (that I can't find now), where someone described exactly this problem as one of a few known issues that Husqvarna were working on, but the author had not been active on that forum for quite some time. He mentioned in the brief comment that it was related to a check valve in the carburettor, I think he said impulse line but I can't find the comment right now.

It's possible that this has always happened with this saw, I'm a home owner with a nice saw because I knew eventually I'd get around to the job I'm doing now. Previously I'd only really do 1 tree at a time, or take enough of a break between cutting to not notice. We finally got around to having 20 trees dropped more safely than I could do them, so now it's clean-up time and I'm out there any time I can get away from work.

Possibly related, it does sometimes (not often) seem to get itself flooded on a restart even though I'm not using the choke (just fast idle). When this happens I can get it started as you'd usually start this saw while flooded (throttle + knee + lots of careful). I think this is unrelated but just thought I'd throw it in here.

Can anyone give me some ideas of where to go from here?
 
Husqvarna dealer told me it was the tank vent when mine and as doing something similar to what yours is going. They changed mine several months ago problem is fixed. Although sometimes after I refuel not always but sometimes it will act flooded when I restart after fueling up. If this does happen I pull over and over on the starter with the throttle held down. It eventually starts.
 
Thanks, I'll see if I can figure out how to test the vent properly. One thing I did test last time the purge bulb wasn't working; I tried purging with the fuel cap off (and the tank full of fuel) and it still didn't purge. Does anyone now if that would rule out the tank vent? Or is that inconclusive?
 
Had something similar once with my 550xpAT, and also warm-start flooding issue. Dealer didn't find anything particular but uploaded latest software in it and works great since. Weird fix for that problem I agree, maybe the carb acts that it drains the fuel lines or something.
 
Had something similar once with my 550xpAT, and also warm-start flooding issue. Dealer didn't find anything particular but uploaded latest software in it and works great since. Weird fix for that problem I agree, maybe the carb acts that it drains the fuel lines or something.
Weird indeed! How far into starting would you get with your problem? Mine won't even spark when it's doing its thing. I'll see how much my local place will charge me for a software update, thanks for the info!
 
Oh I think I was still getting spark. The saw stalled like the engine was starving fuel when hot. Primer bulb went empty. Try to restart her and flood it everytime. Let it sit for a while and starts back as if nothing happened. Other way is to crank her WOT until she starts. Can't explain why the software update changed something, or if when they did they move (without notice) something about the tank vent that went to work after? Anyways, now running fine so i can't complain!
 
It sounds like vapour lock. Restarting while throttle wide open usually gets em going. Not an ideal way to start a saw, but it may work. Primer bulbs don't function under vapour lock, it can be annoying.
 
Ahh yes, The auto tunes are great when they run, but very aggravating when they start this $hit. I am very familiar with the above symptoms.:mad:
 
Weird indeed! How far into starting would you get with your problem? Mine won't even spark when it's doing its thing. I'll see how much my local place will charge me for a software update, thanks for the info!
If you're not getting spark then a software update won't fix the problem and its not AT related.
 
if it has no spark when its acting up then I would check wiring, on off switch,and coil. it has nothing to do with the carb or AT if it doesn't have spark.you can completely remove the wiring and the AT and pull the saw over with a good coil and get spark.
 
Sorry, I think that was me using the wrong wording. I didn't check the sparkplug, I just didn't get enough of an ignition to push the decompression button back up.
 
On vapour lock/tank valve; I assumed opening the tank would balance things out again, which I have tried and it still wouldn't purge. When I tried that it would have been while the saw was already in this state, so my test might have been a bad test. I just read some more on it, and a suggestion on this forum was to open the cap immediately after stopping the saw. I'll give that a try this weekend, thanks for those ideas.
 
Update; opening the tank as soon as I stopped the saw didn't help at all.

I did some more (unscientific) testing, I'm not actually sure that the purge works at all after the engine has been running. The bulb appears to have fuel in it immediately after turning off, but the button still feels too easy to press, and the bulb doesn't get any more full. It seems the fuel either boils off somehow or leaks out somewhere until something unsticks and the purge fills up ready to go again (after some random period of time).

Has anyone got any other ideas for testing? Is it fair to say that I can rule out the tank vent at this point?
 
Has anyone got some thoughts for things I can test over this coming weekend?

Are you trying to start your saw with the decompression valve pushed in? If so, try starting it with that valve in the outward position. My 562XP is very fussy with warm/hot starts, but if I leave the decompression valve alone, it starts in 1-2 pulls (set choke to up position, then flip to middle high idle position before pulling).

Good luck!
 
Thanks for the luck! I think you're right about it starting better with decompression valve left out (while warm), I was experimenting with that last weekend (I came across that in another thread here). It made the starts that did work easier, but didn't help when it was misbehaving. I'll give it another shot this weekend to be sure.
 
Check the fuel line at the carb. Mine had similar symptoms with the addition of running too lean. I noticed that the primer wouldn't pump up every time the saw acted up so I figured it had to be pulling air. It should have been warranty, but the dealer was closed so I opened it myself. When I went to pull the carb the fuel line just fell off. It was swelled up and loose on the fitting. I had a can of fuel resistant sealer on the bench so I smeared some on the fitting and slid the line over top. Let it dry for a bit and went to cut wood. The saw ran perfectly and my hot restarts no longer require shoulder surgery. I've got 4-5 cords under it since and it still runs too good to be worth messing with a new fuel line.

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