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- Apr 27, 2020
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Need some advice on troubleshooting a Stihl MS400c.
The saw originally made it to me with low compression, piston in real bad shape.
I’ve rebuilt the crankcase and put an aftermarket Hyway Cylinder kit on it. Pressure and vac test passed. Carb pressure test good. New bearings, crank seals and spark plug. Air filter and spark screen clean. At this point I have not changed the fuel filter.
I am trying to get it into calibration mode but it won’t stick. The saw starts, kinda idles (doesn’t sound like the normal pulsing sound when the lever is at the triangle icon) then shuts down. I can start the saw with the master lever in the run position and it will ‘idle’ until I stop it, trigger press does not rev the saw much at all - more like it bogs.
So far I have swapped solenoids and the same behavior occurs. I have verified spark is happening.
I’m looking for some advice on other things I could test. I do not have access to an MDG.
Could I test the coil/control unit with a multimeter? I was going to check continuity on the harness next. The harness was replaced several months ago after the owner brought it to me with a broken yellow wire on the carb connector.
If I were to replace the control unit, would it need calibration by a Stihl dealer?
Appreciate any help!
The saw originally made it to me with low compression, piston in real bad shape.
I’ve rebuilt the crankcase and put an aftermarket Hyway Cylinder kit on it. Pressure and vac test passed. Carb pressure test good. New bearings, crank seals and spark plug. Air filter and spark screen clean. At this point I have not changed the fuel filter.
I am trying to get it into calibration mode but it won’t stick. The saw starts, kinda idles (doesn’t sound like the normal pulsing sound when the lever is at the triangle icon) then shuts down. I can start the saw with the master lever in the run position and it will ‘idle’ until I stop it, trigger press does not rev the saw much at all - more like it bogs.
So far I have swapped solenoids and the same behavior occurs. I have verified spark is happening.
I’m looking for some advice on other things I could test. I do not have access to an MDG.
Could I test the coil/control unit with a multimeter? I was going to check continuity on the harness next. The harness was replaced several months ago after the owner brought it to me with a broken yellow wire on the carb connector.
If I were to replace the control unit, would it need calibration by a Stihl dealer?
Appreciate any help!
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