Stihl 042 AVE Help Needed

[Mr BTU]

I have a Stihl 042 AVE that will not stay running. When I start it(w/ choke on) it will start in 2-3 pulls then stall. I turn off the choke it will start right up, rev up then stall after 2-3 seconds. I can repeat this process all day long w/ the same results. I am able to keep it running(I only ran it 5 min at most) by playing w/ the choke. If I choke it approx 90% it will stay running but thats the only way, any less choke it stalls, any more choke it stalls. Here is what has been done so far:

Air filter cleaned
New fuel line has been installed along w/filter
New plug and has nice blue spark
Comperssion check 140 psi cold
Carb cleaned,inspected pump diaphram(ok), checked needle lever height(ok),
verified all low ide ports are clean by spraying carb cleaner through them, removed high speed jet and cleaned, also verified check valve in high speed jet worked by applying a slight vacuum(yes w/ my mouth so keep comments at a min)(ok)
Applied 15 inHg of vacuum to crank case, it dropped to 10 inHg quickly and stopped, then took 10 min to drop from 10 inHg to 5 inHg where it stayed for another 10 min until I opened the valve and then it went to 0 inHg.
Tried to apply pressure to the case but will not hold any pressure, I can apply a couple of PSI to the case but it quickly looses it. I also applied bubble type leak detection to everything on the case while appling pressure and had no bubbles.

I read alot of threads about the crankcase gasket and case screw issues on these 042's which I will be addresing while the saw is on the bench. I suspect an air leak in the case but I am unable to confirm it. I would really like to know what is wrong before I split the case.

Any help/suggestions will be appreciated.

 

[Lakeside53]

Hmmm... kind of holds vac but not pressure...:monkey:


With the case sealed up, pump it up as best you can and keep pumping while you put it in bucket of water - you'll soon see where the leak is.

 

[kevlar]

not pulling fuel? Impulse line?

 

[Al Smith]

I



I read alot of threads about the crankcase gasket and case screw issues on these 042's which I will be addresing while the saw is on the bench. I suspect an air leak in the case but I am unable to confirm it. I would really like to know what is wrong before I split the case.

Any help/suggestions will be appreciated.

That was the main reason they quite making the 042/048 series,case leaks.They are good old saws other than that.

 

[djmercer1]

That was the main reason they quite making the 042/048 series,case leaks.They are good old saws other than that.

are the parts from a 042 interchangable with a 048(im thinking of the big parts such as cylinder, piston ...)? i have access to a couple of 042 that i could use as donor saws for my 048 if compatable.

 

[Al Smith]

Yes as far as I know they will interchange.In looking at the IPL s of both saws it appears the piston and jug are the only thing different other than the various coils ,covers etc.

Hmm,speaking of 048 s,I have a leaker I can't seem to find the time to repair for one reason or another.I imagine it's the clutch side seal,an easy fix if I could just find a half hour or so to get on it.It's a good thing I have a shed full of saws or maybe not so good depending on how you look at it.

 

[stihltech]

gasket

Case gasket is blown out at bottom of crankcase.

 

[Mr BTU]

Bucket of Water Worked, Kind of

I put the engine in a bucket of water and preceded to perform a psi/vac test and it held psi and vac great! After a couple of re-tests w/ the same results and a couple dozen W.T.F.'s I pulled the engine out of the water to double check everything the engine was full of water. I drained it and tried to check it again but it would fill up w/ water. Even though I could not confirm it 100% I split the case and will be installing new oil seals, case seal, and new case bolts.

Thanks for the advice from everyone, it is appreciated.

 

[Lakeside53]

uh oh... NEVER do a vac test under water... only pressure..... the idea is to push air out, not suck water in!

 

[ThoMc]

I have a Stihl 042 AVE that will not stay running. When I start it(w/ choke on) it will start in 2-3 pulls then stall. I turn off the choke it will start right up, rev up then stall after 2-3 seconds. I can repeat this process all day long w/ the same results. I am able to keep it running(I only ran it 5 min at most) by playing w/ the choke. If I choke it approx 90% it will stay running but thats the only way, any less choke it stalls, any more choke it stalls. Here is what has been done so far:

Air filter cleaned
New fuel line has been installed along w/filter
New plug and has nice blue spark
Comperssion check 140 psi cold
Carb cleaned,inspected pump diaphram(ok), checked needle lever height(ok),
verified all low ide ports are clean by spraying carb cleaner through them, removed high speed jet and cleaned, also verified check valve in high speed jet worked by applying a slight vacuum(yes w/ my mouth so keep comments at a min)(ok)
Applied 15 inHg of vacuum to crank case, it dropped to 10 inHg quickly and stopped, then took 10 min to drop from 10 inHg to 5 inHg where it stayed for another 10 min until I opened the valve and then it went to 0 inHg.
Tried to apply pressure to the case but will not hold any pressure, I can apply a couple of PSI to the case but it quickly looses it. I also applied bubble type leak detection to everything on the case while appling pressure and had no bubbles.

I read alot of threads about the crankcase gasket and case screw issues on these 042's which I will be addresing while the saw is on the bench. I suspect an air leak in the case but I am unable to confirm it. I would really like to know what is wrong before I split the case.

Any help/suggestions will be appreciated.

i had the same problem... i found it was a Pin-hole in the boot between the cylinder and the carburetor. replaced the boot and Shasta!! it runs like a top. ThoMc