Echo PB500H backpack blower that’s about 14 years old. Over all, runs well. I’m running into an odd issue where after running for a while at full throttle, the RPMs will randomly drop, then pick up. The longer I run it for, the more pronounced the drop will be. This afternoon, it got the point where the unit would almost stall unless I backed of the throttle. Kinda stumped on this one. Wondering if maybe a fuel line is split and it’s starving for fuel at times? Open to any suggestions.
Fuel or pulse lines would be suspect...or possibly the coil breaking down. Hopefully not something more involved, like crank seals.
I've put a carb on a husqvarna blower once before for what you're describing. That blower had no impulse line to the carb, just a hole in the carb body.
I replaced the carb on this unit as well. I’ll have to take a closer look at the actual setup. Where do you all get fuel line for equipment like this?
I'd probably tend to buy OEM...it's easy to buy the wrong stuff aftermarket...it often says it's tygon, but is not...doesn't last long
I adjusted the carb last weekend and gave it a test this weekend. After it runs for about 10 minutes, it’ll start to drop in RPMs at full throttle. If you don’t back off, it’ll actually stall out. I took two videos and made them in to one; it shows how it drops in RPM, then a drop and complete stall.
If that were mine I'd want to put a spark tester on it, narrow down if it's spark or fuel related. I've also used a spray bottle to mist fuel into the air cleaner as the stumble occurs, if it responds to that, then you likely need to concentrate on fuel delivery...I say likely because it's still possible you have an air leak, but I kinda doubt since it comes and goes like that, and it's just sitting there wide open. Careful with spraying gas, you can have a backfire and fire...BTDT
Good call on the spark tester! I actually have one I used on the sleds to chase down a bad coil (which I ended up finding with a multi meter…go figure!) And I have a zoomy bottle I can use or some “cheater” spray to see if it’s fuel.
Well, bought an OEM coil online, installed, fired right up! Ran great! Then started doing it yet again. Sigh. Back to the diagnosis board if there is such a thing…
If it's easy enough to do, pull the muffler and have a look at the piston to check for any irregularities. Did you install new fuel line/filter? I agree with the tank vent comment above. Run it and when you suspect any stumble at all, crack the gas cap to make sure it's not creating a vacuum that is starving the carb. When it does start to stumble, can you play around with the throttle and keep it running or does it eventually die no matter what?
I have a relatively new Stihl blower. It was doing the same thing. Apparently they were having a problem with the new fuel filters clogging. I removed the filter. Ran it without the fuel filter just fine confirming the diagnosis. Then bought some new filters to replace the old (new) one. No problems since.
Thanks guys! I feel like a dolt for not checking the simple things first. Live and learn! The muffler shouldn’t be bad to remove. I think I’ve had it off before. I’ll check the spark arrester screen too while I’m in there. I haven’t done anything with the fuel lines yet. Despite buying a new set…and a new filter. Sounds like at the very least, I should try pulling the filter and seeing if that helps. That’s easy enough. It will shut off if I keep it going at full throttle. But if I back it off to 1/2-3/4 it’ll keep going. Now that I just read what I typed, maybe it’s more of a fuel issue. Certainly not at spark! LOL.
Where’s the “Feeling rather stupid” emoji? While back, I had bought a kit for new fuel line on Amazon. It came with a generic spark plug, two air filters, fuel line and a filter. I pulled the grommet on the tank yesterday and swapped the filter; left the lines as is. I ran the unit for a good 10 minutes on full tilt.(after letting it warm up a bit first) No stumbling at all. It was a little cooler yesterday evening, so I’ll test it again today. But it appears the sub $2 solution addressed the problem. Hopefully this helps someone out. Start small and work your way up if you plan on tossing parts at it. Guess I now have a spare coil should the need arise.
