Stihl 361 Leaky Carb

[EFSM]

How fast is it leaking? How many seconds from .5 bar down to .4?

 

[16TAF]

How fast is it leaking? How many seconds from .5 bar down to .4?

It held at .5 for about 10 minutes. It’s holding pressure but pushing fuel out of the impulse hole.

 

[16TAF]

I got a new intake boot and impulse line, I’ll get a new tank vent tomorrow. That’s about all I know to do with it. I’m guessing where the carburetor meets the intake boot isn’t making a good seal since two different carburetors leaked from the impulse hole.

 

[hacskaroly]

This is more of a general question for everyone, but shouldn't it be an issue for fuel to be coming out of the impulse hole - shouldn't this just be a pressure/air passage to cause the pump diaphragm to go up/down? If this is the case, I am wondering how the fuel is getting around the gasket/diaphragm. I understand that the pressure/air going through the impulse may have atomized fuel, but should not be enough to be leaking out.

 

[EFSM]

It held at .5 for about 10 minutes. It’s holding pressure but pushing fuel out of the impulse hole.

This is very good. Are you using a black rubber pump diaphragm or a tan Mylar one?

I’m guessing where the carburetor meets the intake boot isn’t making a good seal since two different carburetors leaked from the impulse hole

The boot seal has nothing to do with the “impulse hole leak.” But it sounds like any leakage the carburetor has is so negligible as to have no effect. I have never pressure tested a carburetor for nearly 10 minutes, or even a minute. I expect that the Mylar diaphragm would be more likely to allow some air through it. Hey, rubber tires do over time and they are a lot thicker than a diaphragm.

 

[16TAF]

This is very good. Are you using a black rubber pump diaphragm or a tan Mylar one?


The boot seal has nothing to do with the “impulse hole leak.” But it sounds like any leakage the carburetor has is so negligible as to have no effect. I have never pressure tested a carburetor for nearly 10 minutes, or even a minute. I expect that the Mylar diaphragm would be more likely to allow some air through it. Hey, rubber tires do over time and they are a lot thicker than a diaphragm.

The OEM carburetor has the tan Mylar and the aftermarket carburetor has a black plastic pump diaphragm. I wouldn’t worry about it but it is keeping everything under the cover wet with fuel.

 

[EFSM]

The OEM carburetor has the tan Mylar and the aftermarket carburetor has a black plastic pump diaphragm. I wouldn’t worry about it but it is keeping everything under the cover wet with fuel.

Are you saying that it leaks from .5 bar to nothing in 10 minutes? Or that it takes 10 minutes to show leakage? I think I’m misunderstanding you.

 

[16TAF]

Are you saying that it leaks from .5 bar to nothing in 10 minutes? Or that it takes 10 minutes to show leakage? I think I’m misunderstanding you.

I had the carburetor pressurized for about 10 minutes and it didn’t leak down. I set it down and started something else and didn’t realize it had been so long.

 

[EFSM]

Then I simply can’t see how the carburetor is the source of the leak.

 

[16TAF]

Me either. If I can’t figure it out I’ll send it on its way.

 

[Stump Shot]

This is more of a general question for everyone, but shouldn't it be an issue for fuel to be coming out of the impulse hole - shouldn't this just be a pressure/air passage to cause the pump diaphragm to go up/down? If this is the case, I am wondering how the fuel is getting around the gasket/diaphragm. I understand that the pressure/air going through the impulse may have atomized fuel, but should not be enough to be leaking out.

An internal leaking gasket will do such a thing, basically it's a short circuit of sorts.

 

[16TAF]

I believe I got it fixed. After I put a new intake boot on it stopped leaking. I guess there just wasn’t a good enough seal between the boot and carburetor. I’ve been using it for a few days and it’s stayed dry. I tried the carburetor I got from The Dukes and it wouldn’t adjust on the high jet. I was at 14,500 from one turn out to 4.

Thanks for all the help.

 

[EFSM]

I believe I got it fixed. After I put a new intake boot on it stopped leaking. I guess there just wasn’t a good enough seal between the boot and carburetor. I’ve been using it for a few days and it’s stayed dry. I tried the carburetor I got from The Dukes and it wouldn’t adjust on the high jet. I was at 14,500 from one turn out to 4.

Thanks for all the help.

This makes sense that the fuel was spit back and not leakage through the carb. The inner ring is for sure still on the boot?

 

[16TAF]

This makes sense that the fuel was spit back and not leakage through the carb. The inner ring is for sure still on the boot?
View attachment 479668

Yep, inner ring still there, and the outer one.

 

[EFSM]

Yep, inner ring still there, and the outer one.

I worked on a Stihl 192 that had a deformed boot lip due to the outer ring not being lined up properly during prior carburetor work and it wouldn’t seal right. It sounds like something similar may have happened here. Glad to see you sorted it out.

 

[16TAF]

Well I thought it was fixed. Now I have fuel pushing out of the tank vent. I tried two new vents.