🚨 Stihl MS 250 Chainsaw Engine starts on choke but dies immediately when given throttle
Top Culprit: Torn or disconnected crankcase impulse line
Why It Happens: Flexing rubber lines split with age, venting the vacuum pulses needed to operate the internal carburetor fuel pump diaphragm.
🛠️ The 60-Second Diagnostic Test
- Remove the top shroud and check the small black rubber hose connecting the engine case to the rear air box.
- Pressure-test the fuel delivery line to verify the carburetor pump diaphragm is not receiving crankcase pulses.
💡 The Quick Fix Steps
- Pull out the damaged impulse hose from the tight chassis channel using needle-nose pliers.
- Seat the new heavy-duty rubber impulse line tightly over both the engine case nipple and carburetor block connection ports.