Too much fuel pressure?

[kscycler]

Hope someone can help. Just got back from cutting cedar trees on the pasture (or trying to cut, as you'll see), and my new 16" Craftsman chainsaw was being fussy. I got it started and running, no problem. But after using a full tank of gas, we stopped to take a break. After the break, the silly thing just wouldn't start. I took the top off to see if the primer was working, and it seemed to be. For whatever reason, I pulled the fuel delivery tubing off the side of the carb, and there was a lot of pressure. Fuel just squirted out, quite a lot actually. After the fuel quit running, I re-attached the fuel line and it started and ran fine. Another tank, another break, and the silly thing wouldn't start again. So, I took the fuel line off again, and fuel gushed out. After it subsided, I reattached the line and it started and ran fine. What gives? Is there supposed to be a lot of pressure in this line, or is something misrouted. I'd sure appreciate any help...thanks.

 

[Cut4fun]

Sounds like vapor lock to me.

 

[retoocs555]

You been running it to empty each time? Those saws are a pita to start if you run them dry.

 

[JohnL]

Maybe it's building pressure in the fuel tank as it gets hot. Try opening the gas cap before pulling the line off.

 

[kscycler]

Wow, lots of comments; not much help. As far as running it to empty, that would be hard as it's a new saw and the first time out. As for vapor lock, how does that play into it, as there's so much pressure at the carb inlet, but no vapor in the lines. C'mon, try a little harder....

 

[retoocs555]

Wow, lots of comments; not much help. As far as running it to empty, that would be hard as it's a new saw and the first time out. As for vapor lock, how does that play into it, as there's so much pressure at the carb inlet, but no vapor in the lines. C'mon, try a little harder....

Why couldn't a new saw be run until it's out of gas? As far as fuel pressure, that sounds normal to me if you have a full tank of gas.

If it's still warm you shouldn't need to prime it again after your break.

 

[JohnL]

Running it to empty... Running it until it runs out of fuel. New saw/old saw shouldn't make a difference.

 

[Lakeside53]

The fuel pressure is normal...

 

[Gearhead1]

The primer system on these Craftsman/Poulan saws only works to circulate fuel through the carburetor and back to the tank. It does not enrich the fuel delivery (i.e. squirt fuel into the carb throat) as with older primer type saws, such as the McCulloch primer carburetors. It really is designed to make it easier (fewer pulls) to start a saw that has been sitting because you don't have to pull fuel all the way from the tank.

 

[Crofter]

I believe the inlet needle shuts off on pressure. Tho there is pressure in the tank to fuel pump section of the carburetor, I believe there can still be vapor lock on the delivery side of the pump that keeps the saw from getting fuel. Lakeside 53? Does that sound plausible?

 

[Lakeside53]

I believe the inlet needle shuts off on pressure. Tho there is pressure in the tank to fuel pump section of the carburetor, I believe there can still be vapor lock on the delivery side of the pump that keeps the saw from getting fuel. Lakeside 53? Does that sound plausible?

It's possible, but I rarely see "vapor locks" in modern (separated plastic gas tank) saws. In any case, pumping the bulb would quickly flush gas/vapor though - if you can see gas in the bulb moving, it will get to the metering chamber. Not sure what you mean by "shuts off on pressure". The needle will work just fine with normal (which can be quite high) tank pressures.

Don't assume it's gas - check for spark when hot.

For more general interest, Stihl makes a spark tester called a ZAT-4. It's cheap, but different to most others. This works INLINE with your lead and plug. The saw will start with it in place, and you can watch your spark at different RPM and temperatures. Great for old points based systems where the saws won't rev high - it's immediately obvious when the spark quits...

 

[scottr]

Fussy

kscycler , I looked up the warm starting procedure for the Poulan 2250LE which I think is the same as your saw (36cc and silver muffler ) . First place switch on , then pull choke out and push in to set fast idle , then press primer six times , then pull starter , then blip throttle to idle .

 

[MHawn]

I have an old poulan 2000 that builds pressure in tank saw idles up floods open cap will run fine few minutes then back to running fast