Fuel lines

[redsox1]

I have a Stihl FS 76 string trimmer that I'm having trouble with. It'll start and run for a few seconds and then die. I suspect it's one of the fuel lines (they are original). Anyone know either the diameters for these lines and/or a source to buy a couple feet of each line to try a cheap fix?

 

[Treemonkey1000]

Find a Stihl store near you or Ebay it. Change the in tank filter also. Hopefully you don't have crud in the diapragm of the carb. I don't know the diameter. The guy LDI on here is pretty sharp on that stuff message him maybe.

 

[creekbend]

I agree with the suggestion in regards to contacting your local Stihl dealer. I replace my fuel lines on my Stihl weed eater and chainsaw every three years, whether they need it or not. I do this in the Winter. It saves me having problems during the other times of the year. The tubing is not that expensive. Your dealer should have some in stock. Best wishes.

 

[ricklman]

I don't have Stihl, but on my Troy-Bilt trimmer, it will do the same thing. Will run just about as long as it takes to run the gas out of the primer bulb... I take my foam air filter out, wash it, dry it, reinstall and we're off and running again. Took me forever to figure that one out.

IF Stihl is different, sorry, just been in a similar situation.

 

[redsox1]

Thanks for the info, I'll try cleaning the air filter and pick up some new hose and fuel filter from my local Stihl dealer. I'll update w/ results.

 

[LD1]

Find a Stihl store near you or Ebay it. Change the in tank filter also. Hopefully you don't have crud in the diapragm of the carb. I don't know the diameter. The guy LDI on here is pretty sharp on that stuff message him maybe.

Nope, I dont know what size it is, but I bet it is your problem as well.

Older fuel lines werent resistant to ethanol. This newer gas is wreaking havoc on small engines.

If it is the line that is in the tank, just fish it out and remove it. Then take that with you to a place like napa and they will match it up for you. Thats what I do unless I have a peice the right size laying around from the last time I went to napa for the same reason.

But while it is out, feel the hose. If it has any cracks, is pinched or collapsed, or just feels mushy, 99% sure that is your problem.

And while you are at it, it probabally wouldnt hurt to replace that little filter in there too:thumbsup: And in the future, if you can find a place around you that sells NON-ethanol gas, it is worth whatever they are asking. Around me, its the marathon premium stuff at the local mom-and-pop station. About 75 cents per gallon more than a big gas station by the freeway, but I do a GOOD bit of chainsaw running and only go through maybe 5 gallons a year. So in the grand scheme...its not much. Average user just using a weedeater, I doubt would use more than a gallon or so a year.

 

[redsox1]

Well, replaced the fuel filter and both fuel hoses but no change. It still will run after being primed, but only for 5-10 seconds and it dies. It seems as though no gas is being drawn up the fuel line into the engine and is only running on what is initially manually primed by pushing on the primer bulb. Is this a carb issue?

 

[LD1]

Well, replaced the fuel filter and both fuel hoses but no change. It still will run after being primed, but only for 5-10 seconds and it dies. It seems as though no gas is being drawn up the fuel line into the engine and is only running on what is initially manually primed by pushing on the primer bulb. Is this a carb issue?

Doesnt sound like a carb issue persay. Because the fuel that gets to the carb via primer bulb is having no trouble getting metered into the engine and making it run. It sounds like a problem getting fuel TO the carb.

Now I am not familiar with your machine or carb, so others may be helpful here. But for starters, is the primer bulb cracked? and did you make sure you bought the right sized line? Because if it is able to suck air, it will instead of fuel. If the fuel lines werent a tight fit, it could be sucking air. Or if the primer bulb is cracked, you really wont notice a fuel leak, cause it is under vacuum. But pressing the bulb flows MORE fuel than the carb can suck, so you "may" be overcoming an air leak with the bulb, but the carb cant.

Also, there are a couple of ways the carb can "get" fuel. The most common (I think) is with a diaphram and pulse line/port. It works off the crankcase pressure to "pulse" the diagphram and suck in fuel. The diagphram could be dry-rotted. If you have an external pulse line, it could be off or cracked. If it is via internal passages in the carb and cylinder, they could be plugged.

I dont know how much more I can help from here without knowing for sure what the carb set-up is like.

Do you feel comfortable tearing a carb off and appart????

 

[redsox1]

I did use the right size fuel line and filter (picked up today at Stihl dealer) and they installed fine, nice and tight, even used small cable ties at the ends to really seal it. Not sure about the primer bulb, no obvious cracks but.... Whenever I use them (on this machine and others) they always sound and look suspect to me, the gas seems bubbly (?).
I watched a good you tube of a string trimmer carb rebuild, does that count? Looks doable but other than seeing a blocked passage I don't know that I could identify a problem and would probably end up doing the rebuild w/o knowing if this was the problem in the first place. Sounds like a visit to the Stihl man even though I'd much rather fix it myself. I'll post an update (FYI)when (and if) the problem gets resolved. Thanks for the input.

 

[LD1]

. Not sure about the primer bulb, no obvious cracks but.... Whenever I use them (on this machine and others) they always sound and look suspect to me, the gas seems bubbly (?).

Best way to test them is to unhook the output side and block it with your thumb. Then try to pump the primer. With no outlet, IF there is a crack, Thats where the fuel will go. Try pressing differently/on different areas of the bulb, that way IF it is crack right under your thumb, your thumb might be sealing it.

I watched a good you tube of a string trimmer carb rebuild, does that count?

Only if you stayed at a Holiday Inn Express last night:laughing:

.Looks doable but other than seeing a blocked passage I don't know that I could identify a problem and would probably end up doing the rebuild w/o knowing if this was the problem in the first place. Sounds like a visit to the Stihl man even though I'd much rather fix it myself. I'll post an update (FYI)when (and if) the problem gets resolved. Thanks for the input.

Blocked passages are normally the problem. Best way to clean is with compressed air.

But check the diaphragm too, if it is dried out, or torn, it wont work right. If you decide to tear appart, it would be worth while to get a rebuild kit ahead of time. These are cheap. Usually under $10.

IF you get it appart and have questions, pics are worth a thousand words when it comes to that.:thumbsup:

 

[Jim Thompson]

I did use the right size fuel line and filter (picked up today at Stihl dealer) and they installed fine, nice and tight, even used small cable ties at the ends to really seal it. Not sure about the primer bulb, no obvious cracks but.... Whenever I use them (on this machine and others) they always sound and look suspect to me, the gas seems bubbly (?).
I watched a good you tube of a string trimmer carb rebuild, does that count? Looks doable but other than seeing a blocked passage I don't know that I could identify a problem and would probably end up doing the rebuild w/o knowing if this was the problem in the first place. Sounds like a visit to the Stihl man even though I'd much rather fix it myself. I'll post an update (FYI)when (and if) the problem gets resolved. Thanks for the input.

Might be time for new metering and fuel pump diaphragms. Over time, they will get to where they won't flex, in which case the fuel pump will not pump fuel and the metering diaphragm will not respond to engine vacuum. Kit from Stihl is around $10. New carb would probably be less than $50, some are as cheap as 35. If you choose to replace the diaphragms, also replace the small internal filter screen.
Good luck.

Jim