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View Full Version : Sthil FS90 weedeater fuel filter



Mike Lassiter
10-05-2014, 10:45 PM
My wife was going to run out weedeater while I mowed. She advised she couldn't get it to start. We've had the fuel/oil mix a little while (part of this summer) and she told me she had ran it out of gas the last time she used it.We have about 5 acres or there about to mow, so she will trim around the house and out buildings while I mow. She put gas in the weed eater she said.
Ok, it ran fine the last time used until it ran out of gas. Same fuel poured in this time, but basically emptied the 1 gallon jug. She though the fuel priming bulb was bad. She told me she pressed it down, but it stayed down and wouldn't come back up. Hum!
Yep, fuel primer bulb stays down. I got weedeater to start (cheated and gave a shot of starting fluid) engine ran only with choke fully closed. Seems to be starved for fuel. Removed fuel cap and poured gas out. I can tell it has water in it, as it's cloudy looking. Sent wife to local store and got another gallon and added oil mix and shook real good and poured it in. Still only run with choke closed, and primer bulb still staying down when pressed. Then the light bulb flashed in my head! In tank filter is a water blocking type. The filter is not letting gas thru - that's why the priming bulb stays down. Filter keeping fuel from flowing and primer bulb being held down due to suction.
New filter $5 and have to fish it out of gas tank filler opening to replace. It seems very strange to me that this plastic jug has remained capped unless pouring fuel into something has water in it. It must be condensation from the times the jug has been opened as the last cup full or so of the gallon mixed is the only time to cause trouble.
Thought worth sharing as this could happen to anyone else just like it did us. I could see someone taking weed eater or chainsaw or whatever to shop for a $50+ repair bill for a $5 fix.

Don Morris
10-06-2014, 4:14 AM
I've got the FS110. It's a beast, way overpowered for what I need. I love it. My old Echo lasted a long time but started to cause me problems so I looked hard and long. The Stihl line is hard to beat. Thanks for the headsup. Mine is only a year old, but hopefully I'll remember the post and if the same problem occurs, I'll remember to look for the in tank filter. I use synthetic oil and fresh to reasonably fresh 89 octane gas as recommended by Stihl. The best thing you can do for your equipment is to maintain it well. Usually, that means it lasts the longest. Stihl ain't cheap.

Matt Meiser
10-06-2014, 10:02 AM
I switched to using the canned fuel about 2 years ago. Its expensive, but so is a carburetor and its a lot more convenient. Last round I bought I took a printout from Lowes.com showing a price for 6 at a buck or so less per can less to Home Depot and had them match and take another 10% off. I bought 3 cases. Now that I'm down to a trimmer and backpack blower those should last a good bit of time.

Matt Ellis
10-06-2014, 11:42 AM
The filters can just get gunked up with garbage over time too. I recently replaced the one in my BR320 blower. The blower would idle fine, but when I opened the throttle it would rev, then try to die. Fiddled with it for a few minutes, pulled the filter and put in a new one, runs just as well as it has for the last 10 years. (I think this is the 3rd filter I've replace in it.)

I love Stihl products.

William Payer
10-06-2014, 12:26 PM
Modern 2 cycle engines have carbs with extremely small internal passages in order to meet emission requirements. An oil/fuel mix can quickly gum up those small passages, causing problems. Ethanol, bing hydrophillic, attracts water vapor and once reacted, formed a sludge which can clog passages as well as clog fuel filters within the gas tank, as the OP pointed out. I have a brand new Redmax leaf blower that clogged up 3 times within the first year. The gas was fresh from a source where they sell a lot of premium ( not old gas sitting in tanks) and the oil was top of the line Stihl synthetic. Never less, the carb and or fuel filter gunked up after sitting idle for only one week.
I have had much better results using non-ethanol fuel. It can be gotten at local boat marinas or at certain station in your area(www.pure-gas.org) Since there is no ethanol ( which reacts with moisture to form a gunk-like sludge) the moisture issues and gunking up is virtually non-existant. Non-ethanol gas also retains its octane levels much better over time in storage(stabilized).

ray hampton
10-06-2014, 2:13 PM
My wife was going to run out weedeater while I mowed. She advised she couldn't get it to start. We've had the fuel/oil mix a little while (part of this summer) and she told me she had ran it out of gas the last time she used it.We have about 5 acres or there about to mow, so she will trim around the house and out buildings while I mow. She put gas in the weed eater she said.
Ok, it ran fine the last time used until it ran out of gas. Same fuel poured in this time, but basically emptied the 1 gallon jug. She though the fuel priming bulb was bad. She told me she pressed it down, but it stayed down and wouldn't come back up. Hum!
Yep, fuel primer bulb stays down. I got weedeater to start (cheated and gave a shot of starting fluid) engine ran only with choke fully closed. Seems to be starved for fuel. Removed fuel cap and poured gas out. I can tell it has water in it, as it's cloudy looking. Sent wife to local store and got another gallon and added oil mix and shook real good and poured it in. Still only run with choke closed, and primer bulb still staying down when pressed. Then the light bulb flashed in my head! In tank filter is a water blocking type. The filter is not letting gas thru - that's why the priming bulb stays down. Filter keeping fuel from flowing and primer bulb being held down due to suction.
New filter $5 and have to fish it out of gas tank filler opening to replace. It seems very strange to me that this plastic jug has remained capped unless pouring fuel into something has water in it. It must be condensation from the times the jug has been opened as the last cup full or so of the gallon mixed is the only time to cause trouble.
Thought worth sharing as this could happen to anyone else just like it did us. I could see someone taking weed eater or chainsaw or whatever to shop for a $50+ repair bill for a $5 fix.

plastic jugs will sweat if the temperature are different , cold jug versus hot air temperature

Tom M King
10-06-2014, 8:26 PM
If gas with ethanol in it sits for any number of months, it's going to have some water in it. I only run non-ethanol gas in the small equipment.

If you get it running with new fuel, and still have to keep the choke on to keep it running, check the spark arrestor screen in the outlet of the muffler. Especially if you run the Stihl orange bottle, dino oil, the screen will clog up on the little ones in a few gallons. If black, gunky fuel runs out of the muffler, it's a sure clue that the screen is keeping the motor from breathing out efficiently. Any motor needs to be able to breath out the same amount of air that it takes in to run.

If the screen needs cleaning, there is one screw that holds it in. With the screen out, hold it in an old pair of needle nose pliers, and heat it red hot with a Propane torch. Once cool, rub all the ash off with fingers in an old glove. Reinstall the screen, and it should run like a new one.

If the carb has white corrosion in it from water and ethanol, and it needs to be replaced, you can get decent aftermarket carbs for the motors that size off ebay for about 30 bucks with free shipping.

Stihl is one of my favorite power tool companies, and they are well represented on our farm. I was at a hotel where they were having an annual dealer meeting once for another reason. As I passed the door to the conference room where they were milling about just before getting started, I walked up the podium, and announced that I didn't have anything to do with their meeting, but was a loyal customer. I named off their products that I personally owned, I think about 14 pieces, and received a standing ovation. I took a bow, and walked on.

ray hampton
10-06-2014, 9:02 PM
Modern 2 cycle engines have carbs with extremely small internal passages in order to meet emission requirements. An oil/fuel mix can quickly gum up those small passages, causing problems. Ethanol, bing hydrophillic, attracts water vapor and once reacted, formed a sludge which can clog passages as well as clog fuel filters within the gas tank, as the OP pointed out. I have a brand new Redmax leaf blower that clogged up 3 times within the first year. The gas was fresh from a source where they sell a lot of premium ( not old gas sitting in tanks) and the oil was top of the line Stihl synthetic. Never less, the carb and or fuel filter gunked up after sitting idle for only one week.
I have had much better results using non-ethanol fuel. It can be gotten at local boat marinas or at certain station in your area(www.pure-gas.org (http://www.pure-gas.org)) Since there is no ethanol ( which reacts with moisture to form a gunk-like sludge) the moisture issues and gunking up is virtually non-existant. Non-ethanol gas also retains its octane levels much better over time in storage(stabilized).

I went to the pue-gas site and the stations in KY which sell straight gasoline are not close to me or are unlisted