Impulse Hose

[Koba]

I have an Einhell GC pc 1335 tc that I recently fitted new fuel lines to. Since then the saw runs and revs lean and will not carb tune. It may be an air leak or something to do with the impulse line. The impulse hose seems to run from the cylinder to nowhere and is capped with a screw into the hose.

Can someone give me advice on impulse lines in general and how they are supposed to work?

[lurkalot]

Impulse hose normally fits directly to the back of the inlet manifold, so it provides a pulse for the fuel pump which is built into the carb. Without this connected it won't run properly, and will probably lean out.

[peatff]

Vacuum from the crank case sucks the diaphragm and opens the valve for fuel to enter via the needle. Is there a spare connection on your carb that the hose should connect to? Not all have a separate hose. On some it is just a hole in the face of the carb that covers a corresponding hole built into the manifold wall. Have you had the carb off and checked the diaphragm is still flexible and all the jets and channels are clear? Squirt some carb cleaner through them and clean them out, check the valve and fit a carb kit they are not expensive.

[billpierce]

Potentially the one witha screw in the end is your tank breather rather than impulse?

[lurkalot]

12 hours ago, peatff said:

Vacuum from the crank case sucks the diaphragm and opens the valve for fuel to enter via the needle.

Well,  it does, but not via the impulse hose.  The impulse hose is for the fuel pump side of the carb.

[spudulike]

The impulse line carries the positive and negative pressure in the crankcase in to the carb that moves a pump diaphragm (not the metering one) up and down to pump fuel in to the pump section of the carb and is then allowed in to the metering section once fuel is depleted in the metering section allowing the nipple on the metering diaphragm to push on the metering arm thus opening the needle valve allowing fresh fuel in to the metering section of the carb.

How does that description grab ya?

The OP still has a dodgy Chinese saw though!

[peatff]

1 hour ago, lurkalot said:

Well,  it does, but not via the impulse hose.  The impulse hose is for the fuel pump side of the carb.

You explain it then instead of jumping on someone else trying to do it. 

[lurkalot]

13 minutes ago, peatff said:

You explain it then instead of jumping on someone else trying to do it. 

I didn't jump on anyone.  And did explain it. ;)  The OP asked about the pulse hose. Not the metering system which is separate from the fuel pump.  Spud explained it above.  

[peatff]

 

I over simplified it but in my understanding he asked about what the impulse hose does and it does all the pumping and causes the metering which is the part that is affecting the fact that his saw won't run. Apart from it being Chinese.

Edited November 14, 2018 by peatff
forgot my text

[lurkalot]

Not sure you "simplified" it to be honest.  It doesn't cause the metering, the metering is a separate thing.  It makes the fuel pump work as I already explained.  The pump feeds the metering reservoir.  Metering is a separate operation altogether.    But who am I to speak on such things, I've only been repairing this stuff for 42 years.  In future I'll keep my help and  advice to myself.