Stihl 025 Won't start

[ArchieBennett]

I got my hands on a Stihl 025 cheap as a non-running saw. I do not have a compression tester, but it feels right and I have owned an 025 in the past, replaced it with an MS250 and now bought this one as a back-up saw. I think I am acceptable on compression, but please correct me if that is a naieve assumption. Tried to start it up and no dice so started down "the list"...

I immediately ordered a chinese tune-up kit to get it running and cleaned it up. Even checked the spark arrestor, and it is so shockingly clean I suspect the owners actually cleaned it from time to time as they are supposed to do. It is complete and in pretty good shape physically. Looked at piston while I had muffler apart/off and it looks great - very little use. Some crusties in the exhaust port, but nothing alarming. Anyhow, I put in new fuel line, fuel filter, air filter and manifold, spark plug. Checked spark and had none. Ordered a new coil kit and installed it. I now have good spark - verified both by eye and by tester.

Added new caned pre-mix fuel, tried to start, and nothing. Squirted gas into carburetor throat, and started right up, but ran out of gas after a few seconds, and nothing. Blew some compressed air into the carb intake fitting and fired, but quit right away. That should mean that it can get gas, but after repeating with no better results, ordered a new carburetor from ebay, but did not order from China. Was shipped in a couple days, and not weeks as chinese would have been. Has two screws for High and Low as well as LA - OEM only had low adjustment, but I felt that was a bonus, rather than a bummer. I have a tach and will adjust it appropriately IF I can ever get it running.

It will not start with the new carburetor either. Acts exactly the same as the old carburetor. I even fiddled with the screws some, and no try to fire at all. Do I go stihl OEM Carburetor, keep fiddling with screws, or take it to a dealer? I would like to beat this thing, but am at a bit of a loss. Only other thought I have is that maybe the new fuel line is a bust and has a leak??? No real reason to think so, other than it is chinese which seems a bit judgemental. Not that it is not a well-deserved reputation, but it looked fine going in, and I have no valid reason to be suspicious.

 

[kenton.a.frank]

I got my hands on a Stihl 025 cheap as a non-running saw. I do not have a compression tester, but it feels right and I have owned an 025 in the past, replaced it with an MS250 and now bought this one as a back-up saw. I think I am acceptable on compression, but please correct me if that is a naieve assumption. Tried to start it up and no dice so started down "the list"...

I immediately ordered a chinese tune-up kit to get it running and cleaned it up. Even checked the spark arrestor, and it is so shockingly clean I suspect the owners actually cleaned it from time to time as they are supposed to do. It is complete and in pretty good shape physically. Looked at piston while I had muffler apart/off and it looks great - very little use. Some crusties in the exhaust port, but nothing alarming. Anyhow, I put in new fuel line, fuel filter, air filter and manifold, spark plug. Checked spark and had none. Ordered a new coil kit and installed it. I now have good spark - verified both by eye and by tester.

Added new caned pre-mix fuel, tried to start, and nothing. Squirted gas into carburetor throat, and started right up, but ran out of gas after a few seconds, and nothing. Blew some compressed air into the carb intake fitting and fired, but quit right away. That should mean that it can get gas, but after repeating with no better results, ordered a new carburetor from ebay, but did not order from China. Was shipped in a couple days, and not weeks as chinese would have been. Has two screws for High and Low as well as LA - OEM only had low adjustment, but I felt that was a bonus, rather than a bummer. I have a tach and will adjust it appropriately IF I can ever get it running.

It will not start with the new carburetor either. Acts exactly the same as the old carburetor. I even fiddled with the screws some, and no try to fire at all. Do I go stihl OEM Carburetor, keep fiddling with screws, or take it to a dealer? I would like to beat this thing, but am at a bit of a loss. Only other thought I have is that maybe the new fuel line is a bust and has a leak??? No real reason to think so, other than it is chinese which seems a bit judgemental. Not that it is not a well-deserved reputation, but it looked fine going in, and I have no valid reason to be suspicious.

Aftermarket fuel line? Maybe try OEM I’ve had bad luck with them. Also make sure when you put the air filter intake on you are not pinching the line. I’ve had a customer bring a saw in due to that before. Also make sure the gasket on the motor side of the carb has the hole open for the impulse to feed the carb.


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[HarleyT]

Throw out that Chinese plug and put the old one back in!!!

 

[HarleyT]

Impulse line connected??

 

[ArchieBennett]

Impulse line? The extra hole in gasket is lined up, but is there supposed to be more to it? I will get OEM gas line tomorrow if I can get to a dealer.

 

[HarleyT]

On the inside of the rear handle, there is a nipple that a hose attaches, and the other end goes to the bottom of the block.

 

[HarleyT]

Here is the nipple.

 

[rupedoggy]

No impulse= no fuel
No fuel= no joy

 

[ArchieBennett]

OK - so sorry for the delay - things got crazy this week, and I had to set the saw aside for a bit. Yesterday afternoon I replaced the impulse line, checked over the intake manifold for leaks, replaced fuel line and filter (again) with OEM, cleaned everything again, refilled with fuel. Checked for spark before attempting start, to know everything is back together properly and all is well, and it was just fine. Went to start, and No fuel, no bang, and absolutely no joy! I placed some fuel in the intake side of the carb again, and a solid attempt to run - until out of fuel occured again! Fuel tank is half full, and filter is definitely fully submerged.

Checked tank vent (again) just to be sure all bases are covered, and it is passing air.

I am still convinced it is a fuel issue, but have no clue how it could be with 100% new fuel system from tank to engine...

No idea what to even try next.

 

[Dengel]

How does the intake boot look?

 

[ArchieBennett]

Thanks for the quick reply.

Intake boot looks good - I went over it when I replaced the impulse line. I guess I said manifold above - which is the proper term for the doohickey under the air filter, but I meant to say boot - the rubber part between carb and engine intake port. I also feel like that is proven to be OK since it will fire up with a squirt of gas into the carburetor and run fine (but progressively faster) until it runs out of the supplied fuel. I feel like at that point I have proper suction and function, and wouldn't if the boot had a leak. It has to be before that point, unless I am missing something...

Or am I missing something?

 

[Dengel]

Thanks for the quick reply.

Intake boot looks good - I went over it when I replaced the impulse line. I guess I said manifold above - which is the proper term for the doohickey under the air filter, but I meant to say boot - the rubber part between carb and engine intake port. I also feel like that is proven to be OK since it will fire up with a squirt of gas into the carburetor and run fine (but progressively faster) until it runs out of the supplied fuel. I feel like at that point I have proper suction and function, and wouldn't if the boot had a leak. It has to be before that point, unless I am missing something...

Or am I missing something?

Just trying to check the usual suspects off the list first. Have you checked the meter lever height in the carb?

 

[ArchieBennett]

I have not, but there have been two different carburetors in this thing with the exact same end result. The second one is an OEM replacment - brand new.

How do I check the meter lever? Where should it be? I have done carbs with floats and needle valves, and they are pretty easy to adjust and obvious to get close. I will take it apart and take a look at it, but I find it hard to believe if there was one set wrong, could both be set the same (wrong) way? Walbro has a manual on how to adjust, but all sources I see have a price to be paid for the manual, and frankly, I already have too much invested in this thing. I suspect it is simply bending things to a point it appears appropriate, reassembling thing, and trying it repeatedly until one is successful.

 

[HarleyT]

Cheapo chinese fuel line/filter?

 

[SteveSr]

Have you checked the carb/manifold gasket to make sure that the impulse is actually getting to the carb? A generic gasket might not have the hole, hole in the right place, or the gasket might be upside down. The impulse hole in the carb flange MUST line up and have a clear path to the passage in the handle/housing.

 

[ArchieBennett]

Harley - I had a cheapo line and filter, but replaced that with brand new OEM on Saturday, right along with impulse line.

Steve - I also reassured hole is all good at manifold during that process of changing out the impulse line. I was pretty acutely aware of that after the disassembly process to get there as it made a lot of sense that it was likely the problem once I understood what the purpose/need of the surgery was.

 

[Dengel]

I think the next thing to do is verify that you impulse. Take one of those red straws from carb cleaner or brake cleaner, put it in the impulse line, spray some soapy water on it and turn the crank over. You may have an air leak so massive that it cannot generate impulse enough to push fuel out of the carb. Just a thought. And/or pressure/vac test the crankcase.

 

[rupedoggy]

Good advice Dengel but an impulse does not push fuel but draws it from the tank into the carburetor. Then it may push it to the needle/seat but not out of the carburetor. Venturi vacuum draws the fuel out of the jets.

 

[SteveSr]

Good advice Dengel but an impulse does not push fuel but draws it from the tank into the carburetor. Then it may push it to the needle/seat but not out of the carburetor. Venturi vacuum draws the fuel out of the jets.

Impulse does NOT draw fuel directly. All it does is to move a small diaphragm in the carb back and forth which moves fuel via a couple of flapper check valves (fuel pump) from the tank to the metering chamber.

BTW, this is another way to find out if you are/not getting fuel to the carb. After pulling on the starter or running a slug of gas through the engine remove the carb and open the metering chamber. If it is dry you have a fuel pickup, fuel pump, and/or impulse issue.

 

[rupedoggy]

Impulse does NOT draw fuel directly. All it does is to move a small diaphragm in the carb back and forth which moves fuel via a couple of flapper check valves (fuel pump) from the tank to the metering chamber.

BTW, this is another way to find out if you are/not getting fuel to the carb. After pulling on the starter or running a slug of gas through the engine remove the carb and open the metering chamber. If it is dry you have a fuel pickup, fuel pump, and/or impulse issue.

Wait a minute "does not draw fuel" Well you go on to say it "moves fuel" and then make reference to a fuel pump. Now if a fuel pump does not draw fuel, what exactly does it do? The impulse goes pressure and then vacuum. That moves the diaphragm. That pumps the fuel right? That draws fuel from the tank, right? When the flap allows vacuum to enter the fuel line it draws the fuel to the carburetor. I stand by my original post. No impulse=no fuel.
Before the fuel pump in saws we had to keep the saw level and turn the bar for certain cuts.