parrisw
Tree Freak
Tank Vent?
Dolmar/makita/Solo won't start after hot. Please help
- Thread starter Logger4Life
- Start date
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when this happens, the first thing you think of is that you're out of fuel. you unscrew the gas cap and see that you're still half full. if it was a vent problem, it would be corrected by opening the fuel cap. it seems to be a thermal problem to me.
Are you sure that these saws are flooded? You say that you replaced the spark plug after "8 pulls with the plug out." did you check for a good spark? why did you think they were flooded?
Set too lean and getting too hot or bad fuel. Steve
7sleeper
Addicted to ArboristSite
I totally agree with MCW! 4 saws acting the same since a certain amount of time has to be comon divisor. It's just that simple. I am no mathematican but I presume he could create an equasion to determine the chance for something like this to happen on a different cause than gas, oil or a mix of the two.
MCW rep sent by the way.
7
edit: AAAARRRRGGGHHHHH I hate it when I can't send rep the way I want to....
MCW rep sent by the way.
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edit: AAAARRRRGGGHHHHH I hate it when I can't send rep the way I want to....
parrisw
Tree Freak
Have you done anything with the carbs? Diaphragms nice and pliable?
My first 7900 actually split the fuel tank after suffering from the early series bad breather. I had to get it plastic welded back up and has been fine after updating the breather however poor starting or fuel leakage wasn't one of the issues I had.
Matt: so the vent was failing on pressure direction, not vacuum?
Anyone: what was the improved vent part number, will it retrofit old tanks, and how to tell the difference?
Mine is older, no issues, but better to upgrade if I need to before cracking a tank.
I can't help on the the OP starting issue.
k
Matt: so the vent was failing on pressure direction, not vacuum?
Anyone: what was the improved vent part number, will it retrofit old tanks, and how to tell the difference?
Mine is older, no issues, but better to upgrade if I need to before cracking a tank.
I can't help on the the OP starting issue.
k
PLAYINWOOD
ArboristSite Guru
will a plugged tank vent boil gas or will it cause a vapour lock shutting the engine down?
parrisw
Tree Freak
Plugged vent starves the engine of fuel, the carb can no longer suck fuel, creats a vacuum in the tank, plug the end of a straw and try to suck on it, it don't work.
PLAYINWOOD
ArboristSite Guru
I agree, like 2 stoke carb 101 correct?
So try reading the OP where he states his fuel is boiling..need a link? and your trying to remedy this with a tank vent?
I'm listening..
So try reading the OP where he states his fuel is boiling..need a link? and your trying to remedy this with a tank vent?
I'm listening..
parrisw
Tree Freak
And your trying to remedy his problem by being a d i c k? I'm listening.
I find it very hard to believe that his fuel is boiling. How in the hell would it boil being in a plastic tank and isolated from the engine.
'boiling' is just the liquid turning to vapor. Water does it at 212 F, but fuel does it much lower temp. and the vaporization temp goes down as the pressure goes down, so if the tank vent blocks and it goes to vacuum condition it can very well vaporize and look like 'boiling' at fairly low temps, 100-140F guessing. The pump can't pump and it vaporizes in the inlet side of the pump. If there is a hot spot in the line as it passes by something it can vaporize there. Remember the 'good old days' with mechanical fuel pumps on the side of the V8 engines-they were sucking fuel and prone to vapor lock under these exact conditions. Now, with pumps in the tanks, the lines are under positive pressure and no vapor lock.
but to do it with all 4 saws seems more than justy an isolated tank vent failure. Maybe winter fuel in summer conditions? high alcohol? additives?
but to do it with all 4 saws seems more than justy an isolated tank vent failure. Maybe winter fuel in summer conditions? high alcohol? additives?
7sleeper
Addicted to ArboristSite
I just had a similar situation 2 hours ago. Saw Dolmar/Makita 5001, outside temp~ 10°C, cleaned the carb in the ultrasonic cleaner 3x, (twice with simple green, once only with water), drying with the compressor and cleaned the diagrams with wd40. Reassembled and started like new! Ran great and I cut almost one tankful. Set it down and turned it off. I like taking off the hood to fascilate cooling. All of the sudden I hear a bubbling & hissing sound comming from the saw. I open the gas cap => no difference, the I take off the air filter an see gas bubbling out of the carb. It stopped then and since I wasn't cutting anymore I didn't try to restart. I was just perplex. Will try restarting next week can't run the saw here on the weekend.
Anybody have a idea?
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Anybody have a idea?
7
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Trx250r180
Saw polisher
how are the fuel hoses ? ethonol will make them soft and they can colapse ,how old are the saws ? my 026 was doing similar thing,i put a brand new carb on it ,now its real dependable
zogger
Tree Freak
Not familiar with that saw at all, but some saws have a winter/summer setting. If it has one set it to summer, see if it runs better.
Fuel at the pump changes winter and summer as well, they refine it/formulate it differently. Not sure how that effects running, but perhaps it might be a factor. (fuel is real different all over the country)
MCW
Somebody's talking crap here & it ain't the tree!
Hi Kevin.
That's correct, the vent failed to release tank pressure. I also suspect a weak tank weld between the two halves as well but there is no doubt the excess pressure caused the tank to split along the seam. This was in extreme heat though (over 110°F) and the saw had been left sit so in actual fact was probably even hotter. I have recorded temperatures here in the peak of Summer in enclosed sheds approaching 65°C (149°F) and even in temperatures like that have never experienced hard starting from vapour lock. After the fact I actually recalled excess tank pressure when opening the fuel cap but a blocked breather didn't occur to me until later on. I'm not sure of the updated part number but the older breathers were black foam whereas the new ones are a white ceramic/plastic type material and they push straight into the recess of the older breather.
loganj01
ArboristSite Operative
It was mentioned before that someone suspected the Low Smoke Husqvarna oil might have something to do with this? I don't see how it could, BUT...I ran my 7900 hard all day last Sunday. Ran it out of gas a couple of times. Never took more than two pulls to restart. Back when I was having problems with this saw starting hot, I was using the low smoke Husky oil. Now I'm using Stihl Ultra. Coincidence? Perhaps... There are too many other factors to say for sure but mine is starting great now.
tks matt. will check this weekend.
if the tank held extra pressure, it might push through, but would not vapor lock.
not sure where you are, but I designed a system for Au many years ago. Full power operation design was 122F, and travel & half power design for 131F. Hard to keep oil cool when the air going into the cooler is 140F or more.
Aussies must be tough, or at least smart enough to work at night.....
if the tank held extra pressure, it might push through, but would not vapor lock.
not sure where you are, but I designed a system for Au many years ago. Full power operation design was 122F, and travel & half power design for 131F. Hard to keep oil cool when the air going into the cooler is 140F or more.
Aussies must be tough, or at least smart enough to work at night.....
Edge & Engine
ArboristSite.com Sponsor
Tank vent part number is 957114061. But if there is pressure in the tank, the vent is functioning normally. Pressure can build up (especially in warm weather). Look at a sealed gas can in warm weather, it balloons due to pressure. The vent is a one-way duckbill, it will only allow air into the tank to replaced outgoing fuel, but will allow nothing back out.
check the coil/magneto thingy
had friends small homeowner husky ran great until you stopped it. then never restart until cool. checked carb a lot and everyone wore their arms out. finally, checked spark when hot and it did spark but I thought it was 'maybe a bit weak.'
pulled flywheel cover off and coil was about an eighth inch away from wheel! amazing it left the factory that way. used an index card or two, or maybe a business card to re-gap coil/magneto and fixed.
we all got beefy biceps now.
had friends small homeowner husky ran great until you stopped it. then never restart until cool. checked carb a lot and everyone wore their arms out. finally, checked spark when hot and it did spark but I thought it was 'maybe a bit weak.'
pulled flywheel cover off and coil was about an eighth inch away from wheel! amazing it left the factory that way. used an index card or two, or maybe a business card to re-gap coil/magneto and fixed.
we all got beefy biceps now.
