Poulan Predator 35cc Model P3516PR fuel lines question

[rwh963]

hi,

i recently rescued this saw from my town's metal pile. did a lot of cleaning, etc. would not start using standard method (more about that). i took the plug out, put in a little gas, started up in two pulls.

decided to check out the carb. fuel tank line looked a little brown and brittle. decided to put in a new tank line/filter, an also a line on the bulb that leads to the left side of the carb (that line is wider in diameter than the fuel tank line). i left alone the line that went from the primer back into the tank (return line).

after this, i pumped the bulb, got no gas in the bulb. i new there was trouble with the gas tank cap, so i ordered an OE fuel and oil cap so i would have a good seal on both. after they arrived, i installed, pumped the bulb, dry. i think when i originally tried starting its up, pumping the bulb also left it dry, so no fuel was entering the carb.

i re-lined the way it was when i found it, but maybe i have the lines screwed up. here are a couple of pics of the saw, and new carb lines. looking forward to getting this right. any help is appreciated.

 

[tankman]

That looks correct from what I can see. Make sure the short nipple on the primer bulb has the line coming from the carburetor. The long nipple on the bulb returns fuel back to the tank. The primer actually pulls fuel from the tank through the carburetor then to the short nipple. If your lines are correct and you see fuel moving through the lines when pushing the primer you are getting gas, you probably need carburetor work or better than that, replacement.
Also pull the muffler and look into the cylinder to make sure the piston nor the cylinder are scored.

 

[rwh963]

it's strange. when i push the bulb, i get air noise through the fuel filter in the tank (bubbles), but i am not getting any fuel into the primer bulb.

 

[tankman]

That sounds like you have the lines backwards on the primer. Then you would be pushing instead of pulling the fuel. Not sure but that is my thought.

 

[atpchas]

It's possible the check valve in the bulb assembly is FUBAR. Take the primer assembly out and check if there is suction at the short nipple and pressure at the long nipple. I usually test with a short length of fuel line attached to the short nipple and stick the other end in some liquid (preferably mix but water will work).

 

[rwh963]

found this discussion: https://www.arboristsite.com/threads/have-i-reversed-the-fuel-lines-on-my-purge-bulb.356692/

 

[camel2019]

These seem to be all I work on lately last one(just left today) was from 2009 and looked like it seem some combat. new fuel filter lines carb and spark plug I also had to fix the spark plug wire and the muffler screen was plugged and muffler full of oil. I tuned the carb to canned 40 to 1 and it ran fine sprocket was a bit worn but not my saw.

 

[rwh963]

by reading the above link, i feel the fuel lines are correct. the short line should be pulling fuel through the filter tank line, and excess excess gets pushed back into the tank by the brown line (old line). maybe the bubbling sound is the return line. perhaps the diaphragm is failed.

 

[ChillyB]

Put finger over one of the primer bulb ports. The sucking side goes to the carb. The discharge side goes back to the tank.

Then check that the fuel lines in the tank are right. The vent return line from the primer bulb need be only a short length inside the tank. The carb pickup line should be long enough that the filter stone lays on bottom of tank.

I’m giving very basic advice that you probably understand. Just a long way to say assume fuel lines are completely wrong until verified correct.

 

[rwh963]

thx for the suggestion. yes, the return line is just a stub in the tank. the carb tank line is long with the filter at one end. the sound in the tank must be the return line pushing air through. so, the issue may lie in the carb. the fuel is not flowing through to the primer bulb.

 

[Old2stroke]

Are you sure the "suck" line from the primer is connected to the primer port on the carb and not to the fuel inlet port? If there is any air leak in the fuel chamber of the carb, the primer won't suck fuel. A common problem is a nozzle check valve that is stuck open. A good test is to plug the fuel inlet port on the carb, hook a line to the primer port and suck on it, if you can suck air, there is an internal problem with the carb. As mentioned, there could just be a problem with one of the check valves in the primer itself. Any problems with a primer can be resolved by disabling it, just pull the primer line off the carb, plug it and then push it back on. If there is no problem with the carb or fuel supply, pulling the engine over with the carb on full choke should fill the carb with fuel.

 

[rwh963]

yes, i believe they are correct. the smaller diameter tube runs from the tank to the small diameter port on the right side of the carb. the wider diameter tube runs from the wider port on the left side of the carb to the primer bulb. a return line runs from the bulb to the tank (that is making the air noise when the bulb is pushed.

 

[Old2stroke]

yes, i believe they are correct. the smaller diameter tube runs from the tank to the small diameter port on the right side of the carb. the wider diameter tube runs from the wider port on the left side of the carb to the primer bulb. a return line runs from the bulb to the tank (that is making the air noise when the bulb is pushed.

Sounds right, the bulb is just pumping air and not sucking fuel. As mentioned in previous post, many reasons for this. Try disabling it, it isn't needed for the saw to run and if the choke is good, you will just have to pull the engine over a few more times to start without it.

 

[camel2019]

Sounds right, the bulb is just pumping air and not sucking fuel. As mentioned in previous post, many reasons for this. Try disabling it, it isn't needed for the saw to run and if the choke is good, you will just have to pull the engine over a few more times to start without it.

I have done it for fun a couple times just attached the tank return line to the carb and away you go. For the op the smaller line goes to the right hand side of the carb the bigger line is used for the primer the short line comes from the top nipple on the primer and goes to the carb and the longer one goes to the return. When I replace 1 fuel line I replace all of them just bc the factory stuff is junk.

 

[rwh963]

I have done it for fun a couple times just attached the tank return line to the carb and away you go. For the op the smaller line goes to the right hand side of the carb the bigger line is used for the primer the short line comes from the top nipple on the primer and goes to the carb and the longer one goes to the return. When I replace 1 fuel line I replace all of them just bc the factory stuff is junk.

so this suggestion is to disconnect the bulb line that goes to the carb, disconnect the bulb line that goes to the tank and connect that to the carb instead. then you cannot prime the carb. you'll have enough vacuum pressure to get fuel into the carb?

one reluctance is the return line has not been replaced yet due to it looks like a PITA to do, and looks brown and fragile. if i disconnect and connect it, good chance it will shatter, then i'll have to replace it to test this method.

 

[camel2019]

so this suggestion is to disconnect the bulb line that goes to the carb, disconnect the bulb line that goes to the tank and connect that to the carb instead. then you cannot prime the carb. you'll have enough vacuum pressure to get fuel into the carb?

one reluctance is the return line has not been replaced yet due to it looks like a PITA to do, and looks brown and fragile. if i disconnect and connect it, good chance it will shatter, then i'll have to replace it to test this method.

Just like an older saw pull the choke so it’s closed and pull the cord till it fires then push the coke in and pull the cord again. Realistically if the fuel line is junk then so are the diaphragms in the carb then the return line is easier to replace with the carb off of a rebuild.

 

[Old2stroke]

so this suggestion is to disconnect the bulb line that goes to the carb, disconnect the bulb line that goes to the tank and connect that to the carb instead. then you cannot prime the carb. you'll have enough vacuum pressure to get fuel into the carb?

one reluctance is the return line has not been replaced yet due to it looks like a PITA to do, and looks brown and fragile. if i disconnect and connect it, good chance it will shatter, then i'll have to replace it to test this method.

As mentioned before, to disable the primer simply pull the primer line off the carb and block it by pushing a piece of nail inside it, then push the line back onto the carb. You can't leave the primer port on the carb open as it leads directly to the fuel chamber, connecting a line from the port directly to the tank is not a good idea, if the end of the line in the tank is below the fuel level, it will be supplying unmetered fuel directly to the fuel chamber in the carb and will cause a flooding condition. If the end of the line in the tank is above the fuel level in the tank, it will allow air to be sucked directly into the fuel chamber in the carb and the saw shouldn't even run.

 

[rwh963]

ok, so like a finish nail. but then there is no air pulling fuel through the carb, so how does fuel get into the carb?

 

[camel2019]

ok, so like a finish nail. but then there is no air pulling fuel through the carb, so how does fuel get into the carb?

Choke

 

[Old2stroke]

ok, so like a finish nail. but then there is no air pulling fuel through the carb, so how does fuel get into the carb?

Yes, CHOKE. With the choke closed, intake vacuum caused by the piston going up is presented to the engine end of the carb, pulls the fuel chamber diaphragm down and opens the inlet valve. It's this suction that pulls fuel up the fuel line and into the carb, through the fuel pump and through the inlet valve to the fuel chamber. Does the same thing as the primer, just takes longer to fill the carb, especially if the saw has a long fuel line. At cranking speed the output of the fuel pump is insignificant, it's all about the choke.