Impulse line ?

[quantico]

I have no saw problems.. but want to learn what the impulse line is ?? Is it a vaccum line ? What does it do ?

 

[HarleyT]

It is a path from the lower part of the engine, and sends a pulse to the carb to pump the fuel.

 

[stilh036prohog]

It takes the pressure/vacuum from the crankcase to make the carburetor pump fuel . everytime the piston goes up and down it provides vacuum . the engine just moves air. It's the pulses of air that does the work.

 

[Ozhoo]

The vacuum pulse lifts the fuel pump diaphragm which allows atmospheric pressure to push fuel into the carburetor. The pressure pulse is used to close the inlet side of the fuel pump and open the outlet side, in-turn making the world a better place for you and me.

 

[MacAttack]

On all of my 2 stroke saws etc, the impulse line is a passageway from the carb flange into the face of tbe carburetors. Do they have them with a separate hose on some saws?

 

[stilh036prohog]

No

 

[MacAttack]

No

i didn't think so but i don't have any new / pro saws with the latest technology.

 

[HarleyT]

Here is a ms290 impulse line.

 

[quantico]

Thanks men, i appreciate the info.. i see the term and being an engineer i always want to understand things.. makes perfect sense now.. i can see where the hose leaks or falls off you have a problem. I like bmw's and half the car is vac lines and easily broken plastic cooling system parts.. the rest is too many sensors and far overly complex computer software.

 

[lostone]

On all of my 2 stroke saws etc, the impulse line is a passageway from the carb flange into the face of tbe carburetors. Do they have them with a separate hose on some saws?

Plenty of saws have it run as a separate hose rather than through the carb body. Stihl 029/039/026/036/044/046, Husky 346/372/395 etc. all have one.

However all my Macs and Homelites are like you said and run through the intake block to the carb.

 

[stilh036prohog]

If you had two lines running from the case wouldn't cancel there self. Two lines one for exhaust and one for air. A two cycle is different.

 

[MacAttack]

Plenty of saws have it run as a separate hose rather than through the carb body. Stihl 029/039/026/036/044/046, Husky 346/372/395 etc. all have one.

However all my Macs and Homelites are like you said and run through the intake block to the carb.

I'm curious what is the advantage of that arrangement versus the simple port on the intake flange? A stronger impulse on the carb diaphragm?

 

[lostone]

I'm curious what is the advantage of that arrangement versus the simple port on the intake flange? A stronger impulse on the carb diaphragm?

I honestly don't know why, but I have noticed that of the one's that go through the intake to the carb are clam shell design rather than split case and are horizontal rather than vertical on cylinder (the one exception to this is my Super EZ which isn't clam shell) I haven't gone into my Super XL enough to see if it is clam shell or not. I don't know if that has anything to do with it or not.

Guessing it's just a matter of which way was cheaper or easier for them to produce.

 

[HarleyT]

I would think it has more to do with the anti vibe that the boot and impulse line give things,
but I am just guessing.

 

[lostone]

That would make a lot of since HarleyT.

 

[MacAttack]

I would think it has more to do with the anti vibe that the boot and impulse line give things,
but I am just guessing.

That's a good point, it wouldn't be as easy to maintain the impulse line passage in a flexible carb boot.