I've got a craftsman weed wacker, model 358.791010, that has run great the last five years. This past weekend I was using it and after an hour it felt like it was sputtering like it was getting low on gas. then it just died. It was not low on gas, would not restart and I could see fuel flowing from and thru the primer bulb. When attempting to start it would try to fire and turn over every 6+ pulls.

My first thought was dying/dead ign module, but some online searches say to check compression first.

I cant get any higher than 90 psi. Is my weed wacker toast and in need of replacement?

The ign module is $20, money I would rather put towards a new weed wacker if the low compression is a dead engine.

 

That's fine compression. It is likely around 6.5-7:1 compression, so 90psi is pretty good. It's more likely that the carb diaphragm is solidified from ethanol gas.

 

I don't use ethanol in any of my gas engines. At the end of the model number sticker is (09:18). Does that tell me my expected compression ratio?

 

Most gas has ethanol in it. It causes trouble for small engines because the fuel ports are so small and clog up easily.

A carb rebuild kid for that machine costs about $10 plus shipping. But you might be able to save the old diaphragm if it's not already worn out. Could just be the fuel filter or the fuel port is clogged up.

Watch the first video on how to rebuild a carb. Pay attention to the little mesh screen fuel filter. Then watch the 2nd video starting around 4:00 which shows how to test the carb diaphragm. If it fails the vacuum test you probably need a new diaphragm and have to order the carb repair kit.

Carefully disassemble the carb and after you're 100% sure you've removed everything from the carb body you can clean it out with compressed air and parts cleaner. Then put it back together.

 

Smart man.

I laugh everytime i see someone filling up at the garbage gas pumps.

 

Thanks ya'll. I checked for spark and see great sparks, so it appears that my spark is good, compression is good, so next I will be pulling the carb off. not looking forward to pulling all those tiny parts open but we'll see what happens.

 

There is nothing complicated in there, have at it, you will be surprised how easy it is to rebuild.

Lawnmowers, chainsaws, outboard motors, these carbs are a cinch.

Just don't ask me to rebuild a Quadrajunk 4bbl.

 

from what i been learning lately might be easier just to buy new carb,,,the price of a kit is about half of new carb,,,been using them since you had to pull string out of trimmer head

 

Well, I finally got her up and running. I got lucky and did not need a carb rebuild kit or anything major. I did replace the fuel hoses just because they were worn and discolored. I started disassembling and found loose bolts on the muffler. Odd. Then found the head bolts were also loose. I tightened them up, cleaned the whole outside off with brake cleaner, and soaked the piston, walls, and carb with seafoam for 24hrs. I drained the seafoam, filled with fresh gas. And doublechecked the compression-got 100psi this time. That was much better than the 90 psi. It took extra effort to get her started since the seafoam loosened all that gunk up. I had to put gas in the spark plug hole. After starting up she was blowing lots of white smoke for a couple minutes as she burned off the loosened gunk and seafoam remnants. Note-after seafoaming make sure you don't start it back up in the garage. Whew I had to turn on the fan and open all the doors to air out the garage. lol. So now my baby is back up and running like a beast. Thank goodness, because I wasn't looking forward to shelling out $200 for a new weedwacker. Thanks for the help and advice ya'll.

 

Sounds like vapor lock to me ... happens with my chainsaws when it's really hot out.

 

Thanks flainn, but the problem was the head coming loose from the body. It's working great now.