Stihl 009L - Too Much Fuel Or Not enough Spark?

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ArboristSite Lurker
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Nov 17, 2019
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Cle Elum, WA
Friend gave me his Stihl 009L to work on, initial complaint was that it seemed like it wasn't getting enough fuel. The saw would quit, he'd pull the sparkplug, pour in a little gas/oil mix, install the plug and it would fire briefly.

I got it from him and just to make certain there was a real problem, I attempted to start it and it started fine. I ran it a bit, let it cool. A while later, started it again, it ran fine. I gave it back to him explaining that the saw appeared to work fine.

He used the saw to make 6 cuts through a log that afternoon and then it died again. I got the saw back and ordered a carb kit for it. I inspected all fuel lines, which were in excellent condition, someone must have replaced them a few years ago. The pickup filter wasn't clogged. When I took the carb apart and installed the carb kit, I did not see any evidence of dirt. Regardless, I pulled the high/low adjustment screws and blew out everything with carb/choke cleaner. Re-assembled the carb put it on the saw and attempted to start it.

The saw flooded and I had gas dripping out the exhaust port. I dissassembled the carb and found I'd trapped the spring that closes the fuel lever arm cockeyed. I installed it properly, installed the carb on the saw and tried again. Still flooding behavior. Fuel dripping out the exhaust port, wet sparkplug.

I verified spark by pulling the plug and grounding it to the crankcase, pulling the starter rope. Sure enough, there was spark available. Or so it seemed.

A couple of frustrating iterations of failing to get the saw to start, I began to suspect the ignition, specifically the coil. I ordered a replacement coil and when it arrived, I dissassembled the saw to remove the old coil. I checked the old coil for resistance between the primary and secondary windings. I got zero conductivity from either of the windings to the sparkplug connector. I started to install the Chinese coil and didn't like the oversized oblong holes through the steel plates, fearing the timing might not be what it should be. Plus I needed a couple of washers to put under the Stihl screws to adequately span the oblong holes of the Chinese coil.

At this point, I remembered that Stihl spark plug wires screw into the coil body on a recessed "wood screw". I unscrewed the old wire and measured the resistances. 2.8 ohms on the primary side, about 7.3K ohms on the high voltage side. I tested the conductivity of the old spark plug wire itself and there was none. Voila. Problem found, I thought.

I cut the new high tension wire from the Chinese coil and screwed it to the Stihl coil, reassembled the saw and it fired last night. It was late and I didn't want to irritate the neighbors so started it to adjust the carb adjustment screws this morning and it ran for a while. During the adjustment process, it died and I couldn't get it started again. Soon fuel is coming out the exhaust port again.

This time I pull the carburetor and install another, fresh carb kit. Now I have a handy-dandy WalPro carb arm setting gauge along with a pressure testing gauge, just received from Amazon. I validate the lever arm setting is correct with the gauge and it is. Then I apply the pressure using the test gauge/pump, while sealing the impulse hole in the underside of the carb with my finger. It takes about 30 lbs of pressure to pop the needle off its seat. Somewhere I read that about 5 PSI is right. But I think, what with it taking 30 PSI, the problem should be fuel starvation, if anything.

But it is not fuel starvation. If I disconnect the fuel line from the carburetor, pull the sparkplug and pull the motor over with the plug hole down to allow the excess fuel to be pumped out of the cylinder and out of the muffler, then insert the sparkplug, the motor will start and run until it consumes the fuel in the crankcase.

If I re-connect the fuel line to the carb, the engine will flood again.

Anybody out there have any ideas as to why the motor seems to be getting too much fuel?

The reed valve appears to be in good condition.

The cylinder and piston from what I can see through the exhaust port, are in excellent condition with no scoring or metal transfer. Compression I've not measured, but the saw runs strongly, when it runs properly.

I'm beginning to wonder if the original stihl coil is bad and should be replaced as well.

Is there a way the crankcase could be pulling fuel directly from the tank without going through the carburertor? I wouldn't think so, but I'm not very familiar with design of the fuel tank on the 009L.

I'm at my wit's end with this little 009L and I have a fair amount of patience from having worked on McCulloch Mini-Mac series extensively.

I'd appreciate any insights or suggestions from saw repairmen more experienced than myself.

Ah, bonehead mistake. I had a wrong gasket on the fuel pump side of the carb, so the crankcase port was picking up fuel from the carb through the pulse port in the carburetor. After thinking about where might the crankcase be getting extra fuel besides from the metering system, it had to be the pulse pressure passage in the carburetor, and it was.

Found the right gasket to block off the offending hole, and all is good now.

Chalk that one up to inexperience and not paying enough attention to the configuration of the gasket. Bad!


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