Pressure Testing???

[rahtreelimbs]

I haven't pressure tested a saw in a long time. I have this Stihl 361 that I am working on. Starts and runs ok but once warmed up runs like it has a lean condition. I bought a brand new carb, with all the ethanol BS I thought that was the problem. No dice! Next move is pressure/vaccuum testing. I blocked off the exhaust port, intake port. Put v the piston on bottom dead center and am introducin the pressure/vaccuum thru the spark plug hole......anything I am missing?

 

[gary courtney]

check fuel line first! could be pin hole in line inside tank. then check tank vent

 

[beaglebriar]

Block the impulse line.

 

[a. palmer jr.]

Block the impulse line.

If you block the carb off you probably also blocked off the pulse hole, it's not separate on this model.

 

[beaglebriar]

Not familiar with the particular model.... Just trying to help.

 

[a. palmer jr.]

Not familiar with the particular model.... Just trying to help.

The pulse goes through the base of the carb just like the older saws. I just had mine apart or I wouldn't have known.

 

[Chainsaw Jim]

I haven't pressure tested a saw in a long time. I have this Stihl 361 that I am working on. Starts and runs ok but once warmed up runs like it has a lean condition. I bought a brand new carb, with all the ethanol BS I thought that was the problem. No dice! Next move is pressure/vaccuum testing. I blocked off the exhaust port, intake port. Put v the piston on bottom dead center and am introducin the pressure/vaccuum thru the spark plug hole......anything I am missing?

I don't know if you're already done doing this or not, but you can do it the way you are describing. That is the best way if you've removed the entire intake and you blocked the cylinder intake port directly. Make sure you do another vacuum test with the carb installed to make sure that connection is also correct.

 

[a. palmer jr.]

I'm gonna have several candidates for a pressure test before long.

 

[blsnelling]

The position of the piston won't really matter. Just make sure the exhaust, intake, impulse, spark plug, and decomp are all sealed.

 

[a. palmer jr.]

When pressure testing what psi do you start with? I'm thinking around 10?

 

[blsnelling]

10 is what I do.

 

[David Young]

The position of the piston won't really matter. Just make sure the exhaust, intake, impulse, spark plug, and decomp are all sealed.

I disagree Brad, with applying pressure through the plug hole the transfers need to be open to allow the pressure to go to the base.

 

[rahtreelimbs]

Eventually the pressure/vaccuum will leak past the rings. But why not make it simple and go BDC.

 

[a. palmer jr.]

Someone posted on AS earlier to turn the crank slowly while testing.

 

[lone wolf]

Also move the crank ends up and down while testing a slightly worn bearing and a worn seal may hold until you do this.

 

[bwalker]

Before you go to all this trouble try spraying brake cleaner around likely places for air leaks while the saw is running g and hooked up to a tach. If you have a leak you will notice a change in rpm.

 

[a. palmer jr.]

After getting some answers on another thread I'm kinda believing my saw might not have an air leak, it might just have a kinked fuel line which would cut off the fuel..

 

[redunshee]

Someone posted on AS earlier to turn the crank slowly while testing.

I do this when vacuum testing the seals. Vacuum should move and return to original setting. I always vacuum test as well as pressure test as I've had saws pass pressure test but fail vacuum test. While set up I also pressure test the fuel system and vacuum test the vent system.

 

[redtractor]

I've noticed that the piston will do all the moving by itself when you're changing between pressure and vac.

When using brake cleaner to check for leaks, ours is non flammable, if that's what you were after.

 

[rahtreelimbs]

For finding an air I just put the power head in water up to the base of the cylinder air look for bubbles. I hadn't done a pressure/vaccuum test in a while ....hence the reason for this thread.