Echo Blower Problem

[bill18163]

I have a Echo PB-770H backpack blower. Last April(2018) I had a problem with the engine slowing down and losing power and of course the air output went down also. I had been using the machine for six years with no problems. I looked in the trouble shooting section and subsequently did the following: Replaced spark plug. The gap was over size by .004., Replaced the fuel filter, Replaced the fuel tank vent filter, The main air filter was fine so I didn't replace it. Machine ran great after replacing these parts. Today I was using the machine and it started doing the same thing it did last year. It ran for six years from being new but it's only been a year and its' doing it again. The fuel should be OK because I just mixed a new batch with recently bought gas. I ran the gas in my Stihl weed whacker with no problem today. I checked the plug and it looks fine and the gap is correct. It's only a year old. Air filter looks bran new. Fuel filter looks fine. Only thing left is that fuel tank vent filter but I haven't looked at it yet because it's so hard to get at. Now that vent filter is suspicious because the machine will run for awhile before it starts to slow down. Maybe differential in pressure in the tank(vacuum)? Could that vent filter go bad so quick? Or is there something else I'm missing on this machine? I was going to pull the vent filter tomorrow but is there anything else particular to this machine I should be looking at?

[bgsengine]

check spark arrestor screen, also I believe they have catalytic mufflers, so if poor quality oil was used at some point (or too much oil in a mix batch) the catalyst element can clog up. Though it's possible fuel tank vent (no filter there) may be sticking and causing a vapor lock (try loosening gas cap when it starts losing power) Also, make sure you are using the right spark plug - NGK BPM8Y is the only correct plug - No other brand will work correctly as they don't make any plug that is "just right" to match the BPM8Y.. Using other plugs can cost engine performance by as much as 1500 RPMs (I didn't believe it myself and stuck a Champion CJ7Y in an Echo I was working on , ran it 3 minutes, got 11300 RPMs max, then swapped in a BPM8Y and immediately ran it some more, immediate difference by getting 12,200 RPMs right on spec... just by changing the plug.) Could also possibly have heat related thermal breakdown of the crankcase seals or gaskets (verify carb insulator block is not loose, might wanna do a pressure/vacuum test to see if insulator block cracked, or bad crank seals losing vacuum, etc)

Just by your description however I kinda lean towards the latter - heat related thermal breakdown of the crankcase sealing somewhere...

[bill18163]

bgsengine,
How do I set up for a vacuum test on the crankcase seals and the carb insulator block? I have a vacuum tester with lots of hose adapters left over from automotive carburetor work years ago. I assume I have to connect through the carb somehow? Or am I wrong on that? Let me know. Another thought. The engine runs OK for a short while but then when it's warmed up the problem starts. Thermal breakdown as you mentioned? So if I was to test with vacuum I think I should test with the engine hot. Right? Otherwise if the engine was cold it might check OK. Thanks for the help.
Bill

[bgsengine]

If you have what amounts to a vacuum/pressure brake bleeder tool with a gauge (the gauge is a must) what is done is to block off exhaust and intake ports (if you have the echo tool - basically a rubber flap...) You'd loosen the muffler and carburetor and stick the block off in between the muffler/carb and the ports, snug down to make air tight, and then use the spark plug hole adapter (or craft one) to apply the vacuum and pressure (and if there's an impulse hose separately that feeds carb impulse to work fuel pump, can leave plug in and use that hose, or the hose has to be blocked off too) then you apply maximum 7 -10 PSI pressure reading on the gauge (no more than 10 or you'll blow seals out) and hold for 1 minute, if pressure drops, you got a leak (soap and water around all sealing areas to find leak) , if it holds pressure for 1 minute then you pull a vacuum (14 in/Hg ) and see if it holds vacuum for 1 minute. - If it holds pressure but not vacuum then you got bad crank seals. All tests done on cold engine, can move crank back and forth a bit to see if it might have a worn-in ridge that seals run on that loses pressure or vacuum when moving crank around.

But the Main points: pressure vacuum tool needs a gauge that can read low pressures, intake and exhaust (and/or impulse port) gotta be blocked off, tests done on cold engine. Much easier and quicker to test if you already have the tools (block off tool 91041 , spark plug adapter 91018 are the Echo part numbers) Same vacuum/pressure tester can also be used to test 2-stroke carburetors and primers, fuel lines, and tank vent breather as well, just FYI

heat related issues could also be vapor lock (not very common) , fuel lines can collapse /pinch points/ kink (Outta plan on all new fuel lines every year or every other year anyway, as simple maintenance. Many echo models have RePower or YouCan fuel system kits as well as tune-up kits for that reason)

But from your symptoms, sounds an awful lot like crankcase leaking.. If you get into it far enough to get to the crank seals, after 6 years commercial use, I'd probably be thinking about replacing crank seals anyway just as maintenance... Might want to think about investing in new gaskets too..

Worst case, could be worn out piston rings (but rather unlikely, you'd see that in a compression test cold vs hot, and more likely worn rings would show up worse when cold..)

[bill18163]

BG,
I had a problem with my old vacuum tester and had to buy a new one. I guess being 50 yrs old did it in. Anyway I bought a new one that also will produce pressure as well as vacuum. I also bought a few test tools that will help with analyzing my problem. So, that all took time. But after I got everything I went ahead and tested the crank case for pressure and vacuum. Pressure held at 10 pounds for two minutes rock solid. Needle never moved. Vacuum held at 14 for two minutes solid. Needle also never budged. I am going to get some hose and replace all the hoses and will report back after they are replaced and I do a test run. By the way, I did put in a new vent filter and both the air filter and fuel filter look like new. I replaced them last year. I do not use the machine commercially. I am a home owner and the machine gets used most in the fall for leaves. Other than that it only gets used to blow off the driveway after cutting grass and weed trimming.

[bill18163]

BG,
I know that even with me keeping fresh fuel for my small equipment with stabilizer in it that you can still have problems with the ethanol. So the only thing left that I could think to do was tear the carb down and clean and rebuild it. That cured the problem and the blower runs fine now. One question that I have is about fuel. I have run across information about using higher octane fuel and put stabilizer in it. Have you heard of this? Other thing is can you use old fashion leaded fuel in two cycle engines? There are a few places where I can get it. I know guys that use it in their outboard motors on their boats.
Thanks,
Bill

[38racing]

I see even new pushmowers that specify premium gas. I don't think it's for the octane but the reduced ethanol . I use an no ethanol premium in all my stuff.

[bgsengine]

BG,
I know that even with me keeping fresh fuel for my small equipment with stabilizer in it that you can still have problems with the ethanol. So the only thing left that I could think to do was tear the carb down and clean and rebuild it. That cured the problem and the blower runs fine now. One question that I have is about fuel. I have run across information about using higher octane fuel and put stabilizer in it. Have you heard of this? Other thing is can you use old fashion leaded fuel in two cycle engines? There are a few places where I can get it. I know guys that use it in their outboard motors on their boats.
Thanks,
Bill

helps to understand gasoline and chemistry a bit... octane is, to put it simplest , resistance to volatility - higher compression engines will require higher octane rating to prevent ignition problems - burn quality, flame spread, combustion pressures, spark knock (pre-ignition) among many other factors.. Typical gas you buy at the pump containing 10% ethanol (pretty much a given these days unless they actually *specify* ethanol free) , that ethanol is a contributor to the octane rating of the fuel.. Now, if you get water in the gas, (that's because ethanol absorbs moisture from the air to a saturation point, water/ethanol mix drops out of fuel) .. that loss of ethanol is gonna cut your octane rating 10% or so..

That said, Echo recommends minimum 89 octane fuel (93 would be fine too) , and if you use Echo power blend or red armor mix oil, there's already fuel stabilizer included in the mix oil formula. In a tightly sealed storage, out of direct sunlight and excess humidity, should be good for as long as 2-3 years (at most) ..

For example, I have a small chainsaw of my own I keep around for the once-in a while times I need one.. so far has had the gas (of course we use 89 octane and Echo Red Armor) for the last 3 years, just fired it up a few days ago to demonstrate (I have a couple new boxed units of the same model for sale, so I use mine for a demo unit) and still no problems - Fuel still smells "fresh" (after 30-plus years in this business, I seem to have developed a "nose" for gas.. just a whiff and I can pretty accurately judge how old it is, if it wasn't stabilized fuel to start with..) although I have it on a shop ticket to drain it and change fuel filter and pressure test my fuel lines (only 4-5 hours on the saw, but fuel systems do not age well..)

I would NOT use leaded fuel in a 2-stroke - Most especially not one with a catalytic muffler.... (which is why back in the 70's when Cats first showed up in car exhaust systems, is also when No-Lead fuel became an actual thing at the fuel pump.. I can still remember those 18 gallon fill-ups, and getting change back from the $20 bill handed to the pump jockey..) Also you wanna be sure to not use a outboard or snowmobile 2-stroke oil for high revving modern 2-stroke handhelds.. 2-stroke oil is NOT all the same..

[KE4AVB]

And you find that the rubber parts will deteriorate over time especially once they have been exposed to fuel. I have rebuilt carburetors where they were very clean inside but had rock hard diaphragms. As with anything aging isn't kind in the long run and repairs to equipment due to aging is one of the results. I have seen Tygon fuel line to completely fall that have never seen a drop fuel.

When it comes fuel storage it is important to keep it a tightly sealed container especially with today's ethanol blends. Fuel stabilizers help but if the fuel is left unseal it will lose octane and will dry up leave the stabilizer and other residues behind clogging the passages. I have clean several of personal equipment because of this as the carburetor were vented and during hot summer allowed the fuel to dry up. As BGS ethanol does absorbs moisture and settles out as water and alcohol which a lot of carburetion problems and other carburetor problems like corrosion.

As BGS said some us have developed the smell for bad fuel. Usually to me it smells like old oil based paint that has rancid smell.

[38racing]

My wife has definitely developed the smell for old gas since I carried a dumpster find home in the car trunk. Got into winter so I couldn't pressure wash the liner. Not bad now . replaced it further by carrying some garden mulch. My name's still mud though.