Poulan pro 4218AVHD Fuel Line Replacement

[Christopher Dawley]

Hello,

First off, I was brought here while reading an extensive post by Fish on adjusting a Zama C1M W26B carb.

Now for the nitty gritty,

I am tinkering with a saw for a friend. He asked me to look at it, as I have brought small engines back to life with replacing fuel line and cleaning carb.

On this saw, the Poulan Pro 4218AVHD, it would crank, run for about 5-10 seconds, then die.

Upon checking it out, noticed the fuel line was disintegrated. Replaced fuel line.

Now, for the part that I don’t know. I’m pretty sure I hooked up the fuel line correctly. The carb I am working with is a Zama C1M W26B.

When the carb is on the saw, I have the small fuel line with the filter on it, going into the inlet on the right side of carb.

I have the fuel line on top port of primer bulb going to the inlet on the left side of carb.

I have the fuel line on the bottom port of primer bulb going to fuel tank.

When I prime the carb, I can see fuel coming out of the diaphragm on top of the carb.

I don’t think this is normal, and think something else is going on.

With all of that said, after replacing the fuel line, the saw will only run for 5-10 seconds and quit. It doesn’t matter if it is choked or not.

I think the carb may need to be adjusted as well. I also have the spline tool for adjusting this carb.

Any help would be appreciated.

 

[scottr]

Hey Christopher and welcome to ArboristSite .

I had a Poulan 2025 do the same thing . The inlet screen in the carb was clogged .

The purge bulb is working properly it is pulling fuel from the tank into the carb and pushing air and fuel back into the tank .

The 5-10 second run is using the fuel that the purge bulb pulled into the carb .

 

[Christopher Dawley]

Where it is located on the carb? Do I clean it? Is the diaphragm bad and need to be replaced?

Thanks.

 

[dougand3]

Purge bulb connection: The LONG tube always goes back to the tank. Sounds like yours is correct.

Need to pull carb off saw. Remove 1 big screw plate (fuel pump diaphragm) w/ screen underneath. Also, remove 4 small screw plate (metering diaphragm) and check that, too.
Diaphragms need to be pliable. If stiff or "clack" sound - need new ones.

 

[Christopher Dawley]

Seem to have run into a slight problem. I had the fuel line on the primer bulb backwards. Long tube to carb. Switched it, and now, unable to get gas into the primer bulb.

 

[dougand3]

Fuel line with filter in tank goes to nipple closest to the fuel pump side (1 big screw)
Short purge tube goes to other carb nipple.
Long purge tube goes to tank.
If that is how setup is now, maybe purge bulb defective. Test it outside the saw.
Or carb is blocked inside.

 

[Christopher Dawley]

Found the issue. New fuel line has been pulled off primer bulb and carb too many times. Replaced line.

 

[Christopher Dawley]

Got the saw where it will run at idle and warm up. Tried to follow Fish’s tuning guide, but saw lots of smoke from the bar/chain area. Note: bar and chain removed per his instructions.

 

[dougand3]

Is chain brake engaged? Sprocket bearing failure?

 

[Christopher Dawley]

Chain brake is disengaged, but chain sprocket turns. It appears it is back to the original symptom when I first got it. Rev it up, it quits.

Low mixture and high mixture are set to about 1 1/4 turns back from all the way seated. Idle screw is one turn in.

 

[Christopher Dawley]

Think the chain brake mechanism is broke. Upon further inspection, I can see pieces that are melted/missing.

Can the saw be adjusted without the chain brake mechnism?

I read that you can adjust the idle screw and low/high mixture screws to make the chain sprocket not engage.

 

[dougand3]

Pull the whole chain brake mechanism off. Make sure band is open/disengaged prior to removal. Probably 4-5 screws. Sounds like this saw was piss revved with brake on. May be chassis around oiler is melted.
Strato carb Poulans may need 2.5-3.0 turns out on H-L. Idle screw all the way in till you get it running.

 

[Christopher Dawley]

This carb is a Zama c1m w26b. Tried starting all over with adjustments, only to get same results - only idles, but once pulling the trigger, it dies. Will idle all day long until it runs out of gas, which, I have been using the pre-mix TrueFuel 40:1. Almost out of fuel. Would like to get saw running so it isn’t stalling when pulling the trigger. Best I’ve been able to get was low mixture about 1/4 turn in, idle screw all the way out, high mixture about 1 turn in.

 

[dougand3]

When you adjust H-L screws, you label the position "Out from lightly seated". CW in till lightly seated, then out CCW. Most saws' starting point is 1.0-1.5 out but strato carbs are 2.0-3.0 out.
Have take carb apart yet? Gotta do that...or just buy a new AM carb for $13 on ebay.

 

[Christopher Dawley]

Ok, I’m having a stupid moment. What is a strato carb & what is a AM carb?

All adjustments were done “Out from lightly seated”. I always started the carb 2.0 from lightly seated, then only went in 1/4 turn on L.

I have taken the carb apart and cleaned it with the carb/choke cleaner spray. Diaphragms look good. No noticeable wear.

I have not taken the chain brake apart, as the cover holding the brake handle says under tension. I’ve never got things that use tension to go back together correctly, which is why I haven’t taken it apart yet.

As you said before, it looks to have been piss revved with brake on. All adjustments I did were with the brake off(brake handle away from saw handle).

Now, when I try to pull the brake towards the handle, it does not stay in place.

 

[dougand3]

Brake handle forward toward bar tip (away from saw handlebar) is engaged/ON - the band is tight on the clutch drum/sprocket. It's not going throttle up like that.
If handle won't "click" and stay back near handlebar, chain brake has broken parts - it needs to come off.
Strato is 2 butterfly tall carb. AM = AfterMarket.
Is the carb screen under fuel pump clean?
Is the muffler screen clean?

 

[Christopher Dawley]

Got the brake piece taken off.

Carb screen is clean under fuel pump.

Muffler screen is clean as well.

Will try tuning it with brake mechanism off. Maybe it won’t do too much damage to the saw.

 

[Christopher Dawley]

Well, I was able to get the chainsaw running at idle and give it gas and it not stall with the chain brake mechanism off the saw. While I don’t like that part being off, which is a safety feature, the saw runs great and idles great, while warm. Will have to let the saw cool down overnight and start it up again tomorrow, after I get more pre-mixed gas from one of the big box stores.

Thanks for all of your suggestions. They were a big help in getting the saw running again.

Oh, before I forget, do I need to get a tachometer to verify the engine isn’t red-lining? I only tuned it by ear and listening to the engine. Currently, it is not running too fast, like a saw that is chomping it to bit to tear through some wood at idle.

Thanks again,

 

[dougand3]

Running w/o brake assy won't damage saw. When tuning, you want the saw to 4 stroke/blubber until under load in wood. Watch youtube videos How To Tune a Chainsaw.
See if brake assy needs any parts to be functional. Compare your parts to new parts pics online.