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Poulan chainsaw suddenly won't start?


sjc1701's Avatar
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01-13-15, 09:50 AM   #1  
Poulan chainsaw suddenly won't start?

I was given a Poulan 2150 since it wouldn't start. I have had the same model for many years and recently replaced the fuel lines and gas cap on that saw.... it still starts easy and runs like a champ.

I found the main fuel line had broken up in the saw I was given and put in this one new piece of tubing, fired it up and it ran like a champ. I drained the fuel tank for storage and a couple weeks later took it back out, fueled it up, and couldn't get it to start?? Opened it up again and found the fuel line between the carb and primer bulb had broken so I replace this one and the tank return line..... still won't crank??

Getting spark, plug moisture indicates it's getting fuel.... what the heck could it be and what caused this so suddenly? I'm stumped and before I start randomly replacing parts I'm searching for suggestions.

 
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01-13-15, 12:53 PM   #2  
When in doubt I go for a fuel problem first. Even though your plug looked damp I'd suspect a clogged carb. especially since you've had two sections of fuel line die, possibly leaving debris in the carburetor. Other than that I'd give everything in the fuel system a good looking over. Look for a cracked primer bulb, diaphragm cracked or with a hole, clogged filter screen...

 
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01-14-15, 03:53 AM   #3  
Thanks Pilot Dane,
I've triple checked the fuel lines for any leaks or air bubbles and everything looks good. Kinda thinking the carb might have gotten plugged somewhere too. Before I order a new one I have a question. Many years ago when I worked on the old LawnBoy mowers, they had reed valves to act as a check valve for the carb, do these chainsaw carbs have something similar?

 
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01-14-15, 05:14 AM   #4  
Carb

You may find this video helpful:

https://www.youtube.com/watch?v=K0fKiP_P_i0

 
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01-14-15, 10:42 AM   #5  
Thanks Wirepuller38,
I had a pretty good idea how the carb itself functions and the video explains this very nicely, my real question was about the gas/air mixer flow into the cylinder. Since there are no valves in a 2 stroke, what prevents gas/air flow back into the carb as the piston begins the pressure stroke and the intake ports are still exposed?

 
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01-14-15, 08:26 PM   #6  
The exhaust goes out off the top of the piston and the intake goes in below the piston. The porting pushes air mix from below the piston in the crankcase to the top just after the piston covers the exhaust. Google piston porting and you'll probably find diagrams that explain this better.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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01-15-15, 04:37 AM   #7  
So the Poulan engines use a Piston Port design... right??

Thanks Cheese,
At your suggestion I googled 2 cycle engines. I see that there are basically 3 design types.... piston ported, reed valve, and rotary disc valve designs. I also found a diagram of one using what looked like a lightly sprung intake valve (functionally like a reed valve) serving as a check valve for fuel entering and being pressurized by the crankcase.

From the lack of a direct response to my question about the intake, I will assume that the Poulan engine doesn't use a separate type of check valve.

 
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01-15-15, 05:01 AM   #8  
No reed valve. About as simple as you can make an engine.


 
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01-15-15, 10:50 AM   #9  
No valves. Most of your lawn equipment type of 2-stroke engines will be piston ported since the last 20 years or so I guess. Bigger 2 strokes like lawnboy engines on up to boat motors usually have reed valves. I've never seen any type other than these two although I'm sure they exist somewhere.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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01-23-15, 12:23 PM   #10  
Could it be a trigger problem??

I did notice that the trigger latch didn't seem to hold the throttle on the carb open very far (if at all), with the trigger latched. Purchased a new trigger assembly and installed it only to find the same problem! My 2150, identical to the one I've been messing with, holds the trigger almost wide open when it's latched. The trigger on my saw only let's off maybe 1/8" after latching the trigger open, this new trigger for the other saw looks to let off 3/8" or more and let's the throttle close???

This may be why the darn thing wouldn't start in the first place.... couldn't get a good gulp of gas and air? I don't know.

Question now is why did this go bad in the first place? If it's not the trigger and latch what could it be? I've tried bending the throttle linkage a bit to shorten up the let off, but it won't allow enough travel to get the trigger latched.

What am I overlooking??? Did they send me the wrong trigger??? This one was listed for all 2150 type saws.

This thing really has me scratching my head... any suggestions appreciated.

 
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01-23-15, 08:22 PM   #11  
Pour a little gas in the spark plug hole, put the plug back in hold the throttle wide open and leave the choke open and see if it will start. It may take several pulls. Post results.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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01-27-15, 11:47 AM   #12  
I have a generator (Tecumseh engine) and an old tiller (briggs engine with tank mount carb), both of these I have to start by giving them a shot of gas into the piston. Still trying to figure out how I might be able to temporarily hold the throttle open in this saw, I'm not strong enough to hold it by the handle and pull the starter at the same time (pulls a bit hard).

I just put a new carb on it (H and L adjustments set at a turn and half) and a new plug and still can't get it to even think about starting. I did try putting a little gas into the piston and it won't even cough, but that's with the throttle in the 'fast idle' position, not wide open. She's getting a strong spark with the plug removed and it sounds like it's drawing well (sucking through the carb) when it's spun with the plug out....

 
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01-30-15, 04:47 AM   #13  
Well I finally gave up. Hated to do it since I don't think I've ever had a problem getting a 2 or 4 cycle engine to run (unless it had a major mechanical failure). I'll keep it for now just for parts for my other saw which has ran quite well for many years.

 
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09-01-15, 03:13 PM   #14  
I have a poulan wild thing with similar problems

Trying to start a new thread about my poulan wild thing 2375 can you please tell me how to do that. Thanks .....new to this forum

 
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09-01-15, 03:44 PM   #15  
Please delete this post...accidentally replied to an old post.

 
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09-01-15, 06:55 PM   #16  
Spotzie:

Just back peddle from the individual posts on a topic to the page with the lists of topics. At the top of the page is a "Post New Thread" Click on that and follow it through.

 
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