# Poulan saw floods easily



## nbpt100 (Jun 1, 2015)

I just replace the carb on a Poulan chain saw. Replaced lines, primer and plug as well.

I can get it to start after clearing the flood. I tuned the high and low jets so that it seems to idle fine, have good response and high speed power.

How ever the next day when you go to start it, it floods.. I need to remove the plug and clear out the gas from the crank to get it to start.

It is a brand new carb so I would like to think it is all working well.

Any ideas as to why it floods so easy?


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## 30yearTech (Sep 14, 2006)

You may not have the fuel lines attached correctly, depending on the model, primer generally draws fuel from the tank, through the carburetor and pushes the fuel back into the tank from the primer. Make sure the line with the fuel filter pickup is attached to the line on the fuel pump side of the carb. the line from the side with the adjustment screws should attach to the suction side of the primer and the outlet side of primer attaches to the line that returns fuel to the tank.


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## wa5ngp (Aug 14, 2010)

What model do you have? I have one of the newer 50cc "poulan Pros". If it is warm at all if you choke it then it will flood easily. Furthermore, I have not been able to make it hold an operational carb jet setting from day to day. I have tinkered with this thing a lot and have finally given up and will buy an echo or stihl. I don't like to be defeated by mechanical things but sometimes its just not worth the time to keep fixing it especially if there is something fundamentally wrong. If you do some googling on feedback for poulan you'll find a lot of complaints. Sorry if I sound like a grouch on this comment. Your luck may be better.

don


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## nbpt100 (Jun 1, 2015)

Thanks for the reply's. I have it plumbed the way you say 30 year.

It is a Poulan Pro PP4018 40 CC.

I thought the Poulan Pro's were suppose to be half decent and the plain Poulan was more of an entry level tool.

I will keep trying as I also don't like to be baffled by machines. The only other thing I can think of is that the vent in the gas cap is not working correctly. Pressure may build in the tank from the weather being warmer and it is dumping gas in to the carb.

I seem to get it running good at about 1 /3/4 turns on both the idle and high jets. I did try turning up the mechanical idle so i could lean out the idle jets and maintain a decent idle speed.

Just some thoughts I am throwing around. 
Thanks.


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## nbpt100 (Jun 1, 2015)

Tonight I thought I would play around with this thing again and it flooded so darn easy.

I pulled the gas line going into the pump side of the carb and gas squired out of the line coming from the gas tank. Some gas from the carb squirted but more from the line. How is pressure building up so fast in there? Maybe the lever on the needle is not adjusted correctly? This is causing gas pressure to build up on the metering side and being released back into the tank through the primer lines. Is this plausible? 

Wa5ngp, after drying it out I took your idea and tried to start it tonight with out the full choke, I only primed it with one pump, used a 1/2 choke and after a number of pulls and a tweek of the low jet it started.

The gas cap has a check valve that lets air in but it does not relieve it. Before someone suggests a new cap I don't think that will solve anything.

I am spending way too much time on this but the thought of the needle lever being too high seems like a smoking gun. Any thoughts out there on this?


I let it sit for 10 minutes and it started up again with no choke.


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## geogrubb (Jul 28, 2006)

Sounds like the fuel cap is failing, next time before you shut it off remove or loosen the cap to see if it will help with the flooding. I had a weedeater that would shoot fuel when it was shut off becaue of the cap. Have a good one. Geo


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## wa5ngp (Aug 14, 2010)

just for ref. mine is a PP5020AV so its of the same family as yours. The odd thing about mine is that it worked for a while when it was new. Then over time it just got fussier to start/run. I always used fresh fuel. I tore down the carb, cleaned things up adjusted mixtures. It ran ok for a while (I tank full). Now, it looks like its not getting any fuel to the cylinder at all as the plug is bone dry. I am tempted to tear down the carb again to try to figure out what's wrong but I just don't have the enthusiasm for it because I suspect that it won't stay fixed. I wish I understood why.

Today I looked at an echo about 2x the price. Oddly, the Echo looked less heavy duty (more plastic) but I know that there is just something wrong in these PP. The PP is marketing only. They obviously don't do any extended testing of samples to know what they are shipping. They don't call them keep pullin' for nothing.

Hope your luck is better.


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## nbpt100 (Jun 1, 2015)

Geogrubb, I may be mistaken in my understanding of how the valve in the fuel cap works. I know it prevents a vacuum from building. 

Does the fuel cap have some kind of pressure relief valve that you are saying failed on your Weed eater?

I am not sure if my Poulan has such a feature in the cap?

If someone out there knows the specifics to Poulan please share.


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## wa5ngp (Aug 14, 2010)

I don' t think its the fuel cap vent or if there is one. On mine I can squeeze that primer bulb all I want and all that happens is that it simply pulls fuel thru the carb and dumps it back into the fuel tank so its a closed loop. I have not found that pumping the bulb has caused flooding etc. It does need to be squeezed about 6 times at the beginning as fuel may have drained out of the carb bowl. Of course, I"m no expert but that's how I have experienced it on other chain saws and weed eaters.

Try pressing the bulb with the cap on and with it off to see if there is any difference in action.


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## geogrubb (Jul 28, 2006)

nbpt100 said:


> Geogrubb, I may be mistaken in my understanding of how the valve in the fuel cap works. I know it prevents a vacuum from building.
> 
> Does the fuel cap have some kind of pressure relief valve that you are saying failed on your Weed eater?
> 
> ...


It is not supposed to build pressure, I think it happens when a check valve in the primer fails and as the engine is running the pulse that pumps fuel is also pumping air through the return line, run it for a while and when you shut it off pull the fuel line feeding the carb to see if it shoots fuel out. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

The check valve in the fuel cap (if there is one) allows air to enter the tank so fuel can flow out without a vacuum forming. It's there to prevent fuel from leaking back out the vent, but will also prevent air from escaping and can allow pressure to form. It's not unusual to have pressure build up in a fuel tank. You can pull the line off most any small 2 cycle unit and see a stream of fuel flow out. The inlet metering needle in the carburetor should hold around 10 - 14lbs of pressure before fuel starts leaking through.


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## 30yearTech (Sep 14, 2006)

geogrubb said:


> It is not supposed to build pressure, I think it happens when a check valve in the primer fails and as the engine is running the pulse that pumps fuel is also pumping air through the return line, run it for a while and when you shut it off pull the fuel line feeding the carb to see if it shoots fuel out. Have a good one. Geo


The pulse from the crankcase operates the fuel pump diaphragm, there are positive pressure pulses and vacuum negative pulses on one side of the diaphragm. The other side with the help of little flapper check valves draws fuel from the tank and pushes it into the metering chamber of the carburetor. It does not draw any air into the system that isn't already present in the fuel tank, so it does not build any pressure in the tank from this process. It's not unusual to build a slight pressure in the fuel tank from an increase in temperature or just from vibration or agitation of the fuel, but should not have enough pressure to force the metering needle open. If the fulcrum lever in the carburetor is set to high then the weight of the diaphragm on the lever can lower the amount of pressure that the needle will hold, and allow the carburetor to flood easily.


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## nbpt100 (Jun 1, 2015)

Good comments by all.

I don't have the tool to measure the pressure when the needle valve opens. I suppose I could make one.

If some pressure is normal in the gas tank then the reason for flooding is a poorly-performing needle valve. Sound logical? I am suspicious that there is something wrong with the carb.

To Goe's comment about the primer/air purge check valve. My understanding of the check valve in the air purge is to create a vacuum in the metering chamber of the carb. This vacuum pulls out all of the air and dumps it back into the gas tank. In the process it also sucks out gas. Gas is pulled in from the pump side through the needle valve. If the check valve leaked, it would not move the air and gas very well or not at all. It could even pump air back into the carb. With clear lines you can see the direction of flow and it removing air bubbles. Perhaps Geo meant the diaphragm or reed valve is leaking on the pump side and gas is draining gas through the impulse hole into the crank case. Is that plausible? It sounds like it could be.

This is quite a conundrum.

In summary It does not sound like the gas cap. It does not have a pressure relive valve designed into it, only a check valve to prevent a vacuum.

It could be:
1. A leaking reed valve or diaphram the pump side of the carb.
2. The needle valve is either leaking or opening at too low of a pressure causing too much gas to flow ........even when it may not be running.
3. I am an idiot


If I am off base please call me out. I am trying to solve a problem and learning new things as I go. All new ideas and comments are welcome.


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## wa5ngp (Aug 14, 2010)

#3 applies to me as I bought this thing despite reading all the bad reviews.

Nevertheless, I am wondering if the problem could be the fuel float needle meter in the bowl of the carb sticking, either open or closed? If its sticking open then fuel keeps coming in there which could lead to flooding like you are experiencing.

OTOH, if its stuck closed then no fuel would come in and the situation may be like what I have, that is no fuel is getting sucked in because that bowl is not filling.

I'm calling it a fuel bowl but it is not much more than a quarter sized indentation where a little puddle of fuel is supposed to be sitting. I am trying to get motivated to pull that carb off and take it apart (again).


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## finaprint (Jan 29, 2006)

Last sentence of post #12 getting down to it.

The metering valve is same as float in a bowl type carb with float. Float establishes the working fuel for jets (needles) to work with, float (pulse) going off and the jetting doesn't matter. The pulse amount pumped must just cover the max fuel amount with needles set correctly for max rpm and load and little extra beyond that, if not the pulse fuel amount runs ahead of jetting and same as a float flooding by sticking open. Sometimes you have to set the metering valve a wee bit off what a tool shows, they can be incredibly touchy. I've played hell getting the last .003" needed one way or the other but when you do it then runs perfectly.


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## wa5ngp (Aug 14, 2010)

how critical is the alignment of that tiny spring under that lever arm? I remember reading somewhere there was a suggestion that it was ok to run without that spring. Seems like that would result in extreme flooding. The fact that mine seems to get no fuel at all would suggest that somehow that pulse is not getting to the diaphram or something is blocking that pin.

I can see how poor quality control in this area of the carb could lead to very erratic performance.


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## finaprint (Jan 29, 2006)

Remove that spring and you'll find out soon enough...................DON'T.


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## JedClampitt (Aug 7, 2019)

I have a PP5020av and had to replace the gas lines. I went through a lot of troubleshooting to get it running again. It doesn't run great (and never did) but I am able to saw through logs again. At one point it would not run much past the idle with the gas sputtering from the carburetor, and I couldn't adjust the needle jets to smooth it out. The last thing I did was re-install the original carburetor (after cleaning), and cleaned the spark arrestor screen. My guess is that it was the blocked exhaust that prevented the engine from running properly, and I recommend that you clean or replace your spark arrestor as one of the troubleshooting steps.


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