# Poulan Pro chainsaw starting running problem



## wa5ngp (Aug 14, 2010)

Hi folks,
I've got Poulan Pro 50cc PP502AV with a Zama W47 150a carb.

It has always been a fussy starter/runner. In the past it would run fine but then it might stall out and refuse to start again.

The instructions for starting on cold are set to max choke pull 5x then go to 1/2 choke and pull a couple and then go to normal and start. This is hit or miss and I think I flood it sometimes.

Anyway, now I can't get it started for love or money. So I tore it down and clean rebuilt the carb. Removed needle valves and sprayed carb cleaner thru there. Still can't get it to start. It seems like the primer bulb is pulling air into the line. After several pushes of primer bulb if I open the fuel cap there is a release of pressure as if the primer bulb has presurized the tank. There is also a lot of air in the lines. Maybe the fuel filter is somehow not fully immersed in the tanks fuel? Is it possible that air can get into the line thru those small ports in the carb?

This carb setup has 2 butterfly ports. Main one at the bottom and another one above it that connects thru a rubber baffle. Not sure what that top one does. Perhaps this is an EPA "improvement". I am getting spark. I have set the carb screws to open at 2 turns from fully seated.

My next trick is to shoot some starter fluid in there to see if I can get the thing to fire off.

Any suggestions besides pitch it and buy a stihl or echo?

tks
don


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## paulr44 (Oct 14, 2008)

First, the words "Poulan" and "Pro" don't work together. Anything you can buy in the likes of OPE at a box store isn't Pro grade. You're lucky to find a bar size above 20" there, while we sell the MS880 with bar size up to 59". That's $2K though.
Second, if you paid less than $150 for it, probably not worth your trouble.
Third, if it doesn' have an anti-vibration system (rubber or spring mounts between handle and chassis), it surely isn't worth your trouble.

I may sound jaded, but I've been doing this a long time and many of the box store OPE products are, well for lack of better terms, disposable. I get people in with some of them, and tell them it's like taking a hamster to a vet.

You don't mention if you have spark or compression...these are key. I've seen those box-store vertical cylinder saws often having scored cylinders. Pull the spark plug and check cylinder with flashlight.

The added carb. port is for clean air, or stratified, which yes helps them meet Tier4 emissions standards.

Air in the primer line is normal until it primes, that's it job...in actuality it's air purge primer. Those saws often have rotted fuel lines...which will allow for sucking in air instead of fuel.

Gasoline has a vapor pressure, which explains the pressure release you observe. Winter grade fuel (in northern states) has a higher vapor pressure, making it easier for it to atomize in the cold.

Rule of thumb with ANY 2-stroke. Choke, full or part throttle (automatically part throttle with box-store units these days, with blue choke knob), usually about 3 pulls, it'll FART/FIRE/SPUTTER and die. THEN un-choke it, keeping the throttle locked (push the blue choke in), it should then start. So, choke till it sputters, then no choke. IF YOU think you've flooded ANY carbureted engine, APPLY FULL THROTTLE and keep pulling, usually about 10 or so pulls it'll come to life and clear out. When cars came out with EFI, they had to change WOT from mega-fuel to no fuel for starting conditions as people were used to WOT for flooded car engines...if you're older you might remember this.

You asked and said a lot, hope this helps. Yes, we always try to start a no-start unit on a prime of spray. Add a little WD40 to help with lubrication.


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## paulr44 (Oct 14, 2008)

P.S. If you cut a fair amount of wood as a homeowner, I'd suggest spending the money on getting an MS250 or MS251, and using Moto-mix for storage purposes. Probably last you 10 to 15 years or more with good care, and you won't have the issues you have with box-store saws. I may sound like an ad, but I've converted many box-store customers who come back for other quality products. Sign in a workplace of mine years ago: "The sweetness of low price is long forgotten after the bitterness of poor quality is realized."


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## wa5ngp (Aug 14, 2010)

tks for feedback. Yes, it has compression and spark. In this case its only my time that's being wasted but there is getting to be a limit on that too. I'll pick up a can of starting fluid to see if I can get things rolling.

I am old enough to have worked on carb'd car engines and remember how to unflood them. Also how to step once to set the choke before starting.:thumbsup:

Have to wonder what makes these engines so fussy, the carbs? Do they use zamas and walbros in stihl and echo? 

regards
don


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## paulr44 (Oct 14, 2008)

STIHL owns Zama, so many of their products use them. However they do use Walbro carbs too as of late. As for fussy, I mostly work on commercial grade equipment, and these products aren't very fussy. I could say much, much more but will relent.


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## paulr44 (Oct 14, 2008)

I am old enough to have worked on carb'd car engines and remember how to unflood them. Also how to step once to set the choke before starting.:thumbsup:
regards
don[/QUOTE said:


> Yes, had to push the pedal to let the thermo-spring choke close, and the step cam take it's place holding the throttle open a bit more.


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## wa5ngp (Aug 14, 2010)

When I cleaned/ rebuilt the carb I must have not cleaned something properly or something is still stuck in there. Maybe that spring loaded valve. What is happening is that it immediately gets flooded even w/o choking. With the plug and muffler off when I pull lots fuel gets blown out so something is injecting lots of fuel. With no carb I can use starter fluid to get it to fire off a bit.

Time to pull of the carb and clean/ rebuild again  

This carb operates a little differently than the carbs I've rebuilt on old ryobi weed eaters so maybe I did something wrong on reassembly.

don


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## 30yearTech (Sep 14, 2006)

Make sure you have the purge pump and fuel lines correctly attached to the carburetor as this can cause fuel to be pushed into the metering chamber if improperly attached.


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## wa5ngp (Aug 14, 2010)

I've made that mistake before. :drunk:
However, this time I got the gasket and the pump diaphram in reverse order. Apparently, this gives enough clearance that it causes lots of fuel to flood that chamber no matter choke position.
This is what happens when you tinker with these things too infrequently or get into too big a hurry.


Now its on to tuning those jets. I'll listen to any suggestions or look at links anyone has.

tks
Don


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