Stihl FS 400 won't start

[MW0CBC]

Was running fine yesterday for an hour or so then died and wouldn't restart. Plenty of spark at the plug but the plug was dry as a bone.

 

The priming bulb maintains about 1/8 of it's volume as air which doesn't seem right(!) so I assume I've got air being drawin into the fuel system somewhere. I've hooked out the pickup filter and that seems to be OK. Next is to look at the fuel lines.

 

I presume....that once I've taken the air filter off, I undo the bolt at the bottom of the filter housing and then remove the two nuts either side of the air intake to be able to remove that? Once that's off, I'm not sure how, other than looking for fuel weeps, I can start to track down the problem further. Perhaps just order new fuel intake and return hoses and replace them?

 

If anyone has a copy of the service manual they could link me to, that would also be much appreciated.

 

Ta

 

Denis

[spudulike]

Was running fine yesterday for an hour or so then died and wouldn't restart. Plenty of spark at the plug but the plug was dry as a bone.

 

The priming bulb maintains about 1/8 of it's volume as air which doesn't seem right(!) so I assume I've got air being drawin into the fuel system somewhere. I've hooked out the pickup filter and that seems to be OK. Next is to look at the fuel lines.

 

I presume....that once I've taken the air filter off, I undo the bolt at the bottom of the filter housing and then remove the two nuts either side of the air intake to be able to remove that? Once that's off, I'm not sure how, other than looking for fuel weeps, I can start to track down the problem further. Perhaps just order new fuel intake and return hoses and replace them?

 

If anyone has a copy of the service manual they could link me to, that would also be much appreciated.

 

Ta

 

Denis

 

If the plug is dry, it could be a dodgy fuel filter (possibly worth trying first), split fuel line, blocked carb gauze filter or the diaphragm has gone hard and isn't contacting the metering arm.

 

I did one recently and the fuel filter was 99% blocked up. It let enough fuel through to fire and run for seconds and then pop and that was it. Took a fair while to find as fuel filters rarely block up like this!

 

Other than that, dismantle it like you have said, take lots of photos with your phone as you go, especially the pipe positions and diaphragm positions and you will get there. As you take the carb apart, note where there is no fuel and it will guide you to where the problem may be!

[MW0CBC]

Cheers, Spud. Some good advice in there. I will let you know how it goes.