Leaky Saw = Bad Fuel Line

[West Texas]

I repair local rancher's saws as a hobby; and, received an older 029 that wouldn't start the other day. I cleaned it up, hit the air filter with starter spray and she fired right up; but, would not run. Put it in choke and repeat performance. Turns out later, that it was just left over starter spray. Knowing it was an old saw that had sat in his barn for several years, I thought maybe it needed a carb rebuild kit; so I pulled the carb. When I turned the saw on its side, to remove the topside part of the handle, in order to remove the carb, I noticed fuel leaking from the 'top of the tank' around the fuel hose, or so I thought. I thought that was odd; but, the fuel line itself "looked" good. Much later, much later, a closer exam revealed the fuel hose had small cracks; from sun, weather, whatever exposure. That's why it would not run. Andy told me later that this was a very common problem and that the newer fuel hoses have UV protection. First time I ever had a 'leaky' saw that looked good, so thought I'd share this with AS.

 

[WRW]

So, you're saying that it is more an issue of time and exposure to the elements than use? If so, sounds reasonable.

 

[romeo]

I repair local rancher's saws as a hobby; and, received an older 029 that wouldn't start the other day. I cleaned it up, hit the air filter with starter spray and she fired right up; but, would not run. Put it in choke and repeat performance. Turns out later, that it was just left over starter spray. Knowing it was an old saw that had sat in his barn for several years, I thought maybe it needed a carb rebuild kit; so I pulled the carb. When I turned the saw on its side, to remove the topside part of the handle, in order to remove the carb, I noticed fuel leaking from the 'top of the tank' around the fuel hose, or so I thought. I thought that was odd; but, the fuel line itself "looked" good. Much later, much later, a closer exam revealed the fuel hose had small cracks; from sun, weather, whatever exposure. That's why it would not run. Andy told me later that this was a very common problem and that the newer fuel hoses have UV protection. First time I ever had a 'leaky' saw that looked good, so thought I'd share this with AS.

Hi Tom, I have seen that allot around here with the "desert saws". 100+ degrees can be tough on the rubber and plastic.

 

[Lakeside53]

The older 029/039 hoses almost always "perish" right above where the hose enters the tank. It was traced to being exposed to light getting under the handle.

 

[kevin j]

Feeding through a tank hole is a pain. somewhat easier if bevel the end of the tubing with a Stanley knife, then slide a thick wire inside the tubing. use that as guide. Once inside the tank a bit, remove the wire, grab with hemostats adn pull both ends of the tube tight. Stretching reduces the diameter and it slides right through. Its the first 1/4 inch that drives me nuts. pushing with a tiny needle or pin sort of works.

I use Tygon tubing on the motorcycles, and have used on saws.
Expensive, but holds well in UV exposure and cold temps.

Comments from others more experienced with saws in particular?

 

[Peacock]

Honda EVAP system hose works well too. These hoses are exposed to all sorts of grime, dust and dirt. They generally last the life of the vehicle all the while maintaining less than .010" hg of leak.

 

[safeT1st]

Manometers ?

Honda EVAP system hose works well too. These hoses are exposed to all sorts of grime, dust and dirt. They generally last the life of the vehicle all the while maintaining less than .010" hg of leak.

You've got me curious about your manometer reading . I have a heavy duty background and use them for inlet restrictions , crankcase pressure , exhaust back pressure ,air box pressure ect . We have slack tube and glass tube types . We speak in terms of inches of water(H2O) and/or mercury (HG) . Unless I have mis-interperated you ,what you have described is 0.00491 lbs of pressure or vacuum . What devise do you use to make such fine measurements ?

 

[Peacock]

hahaha.......you caught me! I was standing here at work looking at the 'smoke machine' that we use to test the evap systems when I typed that. It lists 2 scales. I just brain farted and wrote the typed the wrong one.:censored:

Ours is glass tube. Can determine down to .010"water. Will find .030" with smoke pretty easily. The natural vacuum leak detection that the PCM monitors will determine leaks below that.

 

[safeT1st]

That's one sharp eye ?

hahaha.......you caught me! I was standing here at work looking at the 'smoke machine' that we use to test the evap systems when I typed that. It lists 2 scales. I just brain farted and wrote the typed the wrong one.:censored:

Ours is glass tube. Can determine down to .010"water. Will find .030" with smoke pretty easily. The natural vacuum leak detection that the PCM monitors will determine leaks below that.

Personally I would have to use a 10X glass to read 0.010" of water at the meniscus level . Even then I couldn't be that sure . 0.010" of water transcribes to an even lesser reading of 0.000361 psi . To find leaks in a tiny fuel line on a saw I would access the line as best as possible and put 5 psi regulated air to the filler opening with shop rag wrapped around nozzle and look for leaks , a little tissue paper dabbed in the crannys shows them up well . Alternatively , 5 lbs to dry tank and soapy solution sprayed about line . Better yet , if in question replace the $ 1 peice of tube . I'm not trying to be arguementative with you but I don't follow your ideas . What is this PCM you speak of ?

 

[Lakeside53]

Feeding through a tank hole is a pain. somewhat easier if bevel the end of the tubing with a Stanley knife, then slide a thick wire inside the tubing. use that as guide. Once inside the tank a bit, remove the wire, grab with hemostats adn pull both ends of the tube tight. Stretching reduces the diameter and it slides right through. Its the first 1/4 inch that drives me nuts. pushing with a tiny needle or pin sort of works.

I use Tygon tubing on the motorcycles, and have used on saws.
Expensive, but holds well in UV exposure and cold temps.

Comments from others more experienced with saws in particular?

It's easier on Stihls - they have a moulded hose/tank grommet. A little oil, grab from below with hemostats, gently pull while pushing from the top with a small punch or blunted screwdriver. I can do the 029 in a few minuets now -don't even take off the handle (but I've has some practise! ).

 

[Peacock]

Personally I would have to use a 10X glass to read 0.010" of water at the meniscus level . Even then I couldn't be that sure . 0.010" of water transcribes to an even lesser reading of 0.000361 psi . To find leaks in a tiny fuel line on a saw I would access the line as best as possible and put 5 psi regulated air to the filler opening with shop rag wrapped around nozzle and look for leaks , a little tissue paper dabbed in the crannys shows them up well . Alternatively , 5 lbs to dry tank and soapy solution sprayed about line . Better yet , if in question replace the $ 1 peice of tube . I'm not trying to be arguementative with you but I don't follow your ideas . What is this PCM you speak of ?

Hmmm....understand your skepticism. I'm just reading what the machine says. Unless I'm misinterpreting it, which is likely. You know more about pressures on this scale than I.

The Powertrain Control Module uses the bypass solenoid, canister vent valve and purge solenoid to manipulate the evaporitive emissions system and the fuel tank pressure sensor to read it all. It uses the purge solenoid operated by pulse width modulation to adjust the fuel tank vapor pressure.

 

[safeT1st]

Fair enough

Hmmm....understand your skepticism. I'm just reading what the machine says. Unless I'm misinterpreting it, which is likely. You know more about pressures on this scale than I.

The Powertrain Control Module uses the bypass solenoid, canister vent valve and purge solenoid to manipulate the evaporitive emissions system and the fuel tank pressure sensor to read it all. It uses the purge solenoid operated by pulse width modulation to adjust the fuel tank vapor pressure.

You are obviously in an automotive shop dealing with various ECU's (electronic control units ) which have workings within them that are beyond me . All in all really not applicable to finding leaking fuel lines and replacing them on chainsaws . Forgot to mention to plug fuel tank vent before applying regulated air to opening . Fun to banter back and forth Peacock and there are many areas I don't have a clue about .

 

[Peacock]

Fun to banter back and forth Peacock and there are many areas I don't have a clue about .

You and me both.

Check your rep!!