Roy Najecki
ArboristSite Lurker
I have a Stihl 026 Pro that won’t start. I have owned this chainsaw since 1998. Two days ago it ran out of gas while running, but wouldn’t start after I refilled the gas tank. I’ve read some threads on starting problems with a 026 and have done the following. I replaced the spark plug, and checked the spark – all is okay. I removed the Walbro WT-426 carb and cleaned all ports with spray carb cleaner, including the H / L ports with screws removed. The inlet screen had a coating of brown gel-like substance which I cleaned away. In hindsight, perhaps that’s why the saw ran a bit sluggish recently. The engine runs for a few seconds if I put a small amount of gas/oil mix in the carb throat. The engine isn’t grounding out – I’m watching the little brass bar that it doesn’t touch the spring. The carb membranes and gaskets are clean and in good shape. The float needle looks good and I wiped it clean. The fuel line is intact and clear, and filter is clean. The piston cylinder is not scored. I examined the impulse hose and it looks okay – if there is a crack in it, I can’t see it.
I tried putting a little oil in the impulse hose to see if it got sucked in/out when I pull the cord. I couldn’t tell as the oil seemed to just flow down the hose. I did attach a vacuum gauge to the hose and pulled the cord. The vacuum gauge needle jumped a little, but in the direction it would go if the impulse hose was pushing air out. I then attached a vacuum pump to the impulse hose to see if would hold a vacuum. It didn’t hold any vacuum. I tried this with the piston all the way down, part way down, all the way up, etc... Since the piston rings aren’t below the level of the carb throat hole I really didn’t expect to see a vacuum created anyway.
I reassembled the carb and tried to start the saw. No luck. But as before, with a little gas/oil mix poured down the carb throat it does run for a few seconds. I pulled the carb out again, removed the metering chamber cover and gas is in the chamber. The spark plug is dry.
So I’m thinking either the carb is bad, or there is a crack in the impulse hose I can’t see. But if the impulse hose was bad, fuel shouldn’t be getting to the metering chamber – right? Since it might take a while to disassemble the saw handle from the crankcase I don’t want to do it unless the impulse hose is the likely problem. (I have never taken a saw apart before.) Assuming it’s not the hose, is my choice then either a new carb, which would be a WT-194 ($45) or try the K20-WAT carb kit ($15)? Or should I disassemble the handle/crankcase and check the impulse hose? BTW – the parts manual says I should have a WT-403A carb on the 026 Pro, but my carb is marked WT-426.
Your thoughts?
I tried putting a little oil in the impulse hose to see if it got sucked in/out when I pull the cord. I couldn’t tell as the oil seemed to just flow down the hose. I did attach a vacuum gauge to the hose and pulled the cord. The vacuum gauge needle jumped a little, but in the direction it would go if the impulse hose was pushing air out. I then attached a vacuum pump to the impulse hose to see if would hold a vacuum. It didn’t hold any vacuum. I tried this with the piston all the way down, part way down, all the way up, etc... Since the piston rings aren’t below the level of the carb throat hole I really didn’t expect to see a vacuum created anyway.
I reassembled the carb and tried to start the saw. No luck. But as before, with a little gas/oil mix poured down the carb throat it does run for a few seconds. I pulled the carb out again, removed the metering chamber cover and gas is in the chamber. The spark plug is dry.
So I’m thinking either the carb is bad, or there is a crack in the impulse hose I can’t see. But if the impulse hose was bad, fuel shouldn’t be getting to the metering chamber – right? Since it might take a while to disassemble the saw handle from the crankcase I don’t want to do it unless the impulse hose is the likely problem. (I have never taken a saw apart before.) Assuming it’s not the hose, is my choice then either a new carb, which would be a WT-194 ($45) or try the K20-WAT carb kit ($15)? Or should I disassemble the handle/crankcase and check the impulse hose? BTW – the parts manual says I should have a WT-403A carb on the 026 Pro, but my carb is marked WT-426.
Your thoughts?