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General Forestry => Chainsaws => Topic started by: sbishop on November 22, 2020, 03:39:40 PM

Title: 034 Stihl stops after 10-15 min
Post by: sbishop on November 22, 2020, 03:39:40 PM
Hi everyone, 

About a month ago my Stihl 034 started to bog like it was missing fuel, come to find out my fuel line was leaking at the grommet. Put a new fuel line and filter and now it will run for 10-15 min really good and shutoff. Starts up fine next day. Any suggestions where to start? Thanks 
Title: Re: 034 Stihl stops after 10-15 min
Post by: sawguy21 on November 22, 2020, 04:17:49 PM
Did you replace the filter while you at it?
Title: Re: 034 Stihl stops after 10-15 min
Post by: sbishop on November 22, 2020, 06:47:14 PM
Yes new fuel line and filter. Tried 2 new spark plugs too
Title: Re: 034 Stihl stops after 10-15 min
Post by: Hilltop366 on November 22, 2020, 07:04:16 PM
Stops suddenly now like was turned off or like it is running out of fuel?
Title: Re: 034 Stihl stops after 10-15 min
Post by: Al_Smith on November 22, 2020, 10:31:01 PM
A wild guess .I 've never had it happen on a Stihl product but I have on McCulloch .Every so often after enough heat build up the ignition coil will fail .
On those saws the designs are different and because of the coil placement I would think the Stihl would cool better .On the McCulloch with a horizontal cylinder chips  and crud would block the air flow under the cylinder .,Easy fix once you figure it out .
Title: Re: 034 Stihl stops after 10-15 min
Post by: sbishop on November 23, 2020, 09:18:12 AM
i'm pretty sure i've eliminated the coil as it won't start up at all this morning. checked for spark and there is lots. i did remove the vent and both screws and blew things out. tried starting it and it would kick a bit, run for a second or 2 and die. 

i'm about to remove the carb and see if its dirty. i don't have a carb kit for it but i'm thinking of tearing it apart, cleaning it and putting it back together to see if it helps.

Sbishop
Title: Re: 034 Stihl stops after 10-15 min
Post by: sbishop on November 23, 2020, 01:21:48 PM
took the carb apart and gave a good blowing with compressed air. wasn't as dirty as some i've seen on youtube.

still the same. i also checked the compression and i'm reading around 80 psi when cold. i can't tighten the compression tool i've as it has a long threads and i can't scew it all the way in without it hitting the piston.

once in a while it will start and idle, thats it once i touch the gas it shutsoff.

Thanks for any help.
Sbishop
Title: Re: 034 Stihl stops after 10-15 min
Post by: ladylake on November 23, 2020, 01:54:58 PM

 Pull the muffler and check the piston for scoring which could have happened if running lean from a fuel supply problem.  If really only 80# compression that's way too low.  Dont be running saws when they sound like they're running out of fuel, they will score the cylinder fast.  Steve
Title: Re: 034 Stihl stops after 10-15 min
Post by: ZeroJunk on November 23, 2020, 04:35:22 PM
It really shouldn't run at all at 80 PSI .  But, it is hard to get an accurate compression reading on a small displacement engine.  Still, I would bet you need a rebuild.
Title: Re: 034 Stihl stops after 10-15 min
Post by: sbishop on November 23, 2020, 07:36:46 PM
i was able to get a better compression tester, i'm getting around 120psi when cold.

i know its fuel related because if i pour a little bit of gas in the carb it will fire right up for few seconds.

things that are new
fuel line, fuel filter, gas
spark plug, last of spark, tried 3 different plugs, lots of spark

things ive looked at
impulse line is good
carb apart twice and everything cleaned, wasn't really dirty
spar arrester screen, looks like new
fuel vent, removed both screw and blew air thru it...put back the screws

i saw a video that a guy had similar issue and it was fuel cap. i ordered a new one, will be here on wednesday. Anyone ever had fuel cap issue?

what would be the factory setting for the fuel / air screws?

Thanks
Sbishop
Title: Re: 034 Stihl stops after 10-15 min
Post by: ZeroJunk on November 23, 2020, 07:56:46 PM
Coincidentally, I took the carb apart on an 034 Super twice last week.  It would just creep up past 14,000 RPM regardless of the hi needle position. Might start out fat and just keep leaning out.  I put a new kit in it and had it clean as a pin. No matter. I put a new $20 Chinese carb on it and it settled down and ran fine.
Title: Re: 034 Stihl stops after 10-15 min
Post by: Real1shepherd on November 24, 2020, 09:27:28 AM
Quote from: sbishop on November 23, 2020, 07:36:46 PM
i was able to get a better compression tester, i'm getting around 120psi when cold.

i know its fuel related because if i pour a little bit of gas in the carb it will fire right up for few seconds.

things that are new
fuel line, fuel filter, gas
spark plug, last of spark, tried 3 different plugs, lots of spark

things ive looked at
impulse line is good
carb apart twice and everything cleaned, wasn't really dirty
spar arrester screen, looks like new
fuel vent, removed both screw and blew air thru it...put back the screws

i saw a video that a guy had similar issue and it was fuel cap. i ordered a new one, will be here on wednesday. Anyone ever had fuel cap issue?

what would be the factory setting for the fuel / air screws?

Thanks
Sbishop
Depends on how that saw is vented;through the gas cap and/or typically, it's own venting system. Check all that out to make sure air is coming in to replace the gas going out.

If you don't have any air leaks, you have hot spark and you replaced the fuel line/filter....I'm gonna bet it comes down to your carb. It doesn't sound to me like you've really cleaned it the traditional way;break it all down, put it in the sauce and/or an USC and then a complete rebuild kit.

The carb kits are less than $15 and so all you really have into it is your time. I'm not a big fan of just blowing through orifices with carb cleaner and calling it good. With Tilly carbs for example, you have to remove/replace Welsh plugs and put in new screens....lots of places to trap dirt that spraying carb cleaner won't get.
 
Kevin
Title: Re: 034 Stihl stops after 10-15 min
Post by: Al_Smith on November 24, 2020, 09:52:32 AM
Carbs can be funny .Recently tinkering with a freebie McCulloch blower it had both the fuel line supply and the return from the bulb primer rotted off .The little tiny Walbro carb I just knew needed a rebuild but I didn't have a rebuilt kit .Much to my surprise the diaphragm and check valves were still flexible .I just put it back together and low and behold it runs like a top .That doesn't happen that often .
Title: Re: 034 Stihl stops after 10-15 min
Post by: dougtrr2 on November 24, 2020, 10:09:25 AM
Yes, I had a fuel cap issue on my Stihl 032.  And now looking back I think the plugging wasn't solid and shifted.  That is sometimes it was plugged and sometimes it wasn't.  The saw would lose power and die.  I would pull the cap to check the fuel, try it again, and it would run for a while.  Once I finally replaced the cap my problems went away.  I am still using the saw, bought new in 1983. 

A few years ago I had ignition issues.  As it turned out it was the spark plug wire itself.  Replacement coils were not available.  I was ready to get a new saw.  At the last minute I discovered that the spark plug wire was NOT molded into the coil.  It actually "screwed" in.  I unscrewed the old wire, put in a new one and I am still running.

Doug in SW IA
Title: Re: 034 Stihl stops after 10-15 min
Post by: Real1shepherd on November 24, 2020, 10:50:12 AM
Quote from: dougtrr2 on November 24, 2020, 10:09:25 AM
Yes, I had a fuel cap issue on my Stihl 032.  And now looking back I think the plugging wasn't solid and shifted.  That is sometimes it was plugged and sometimes it wasn't.  The saw would lose power and die.  I would pull the cap to check the fuel, try it again, and it would run for a while.  Once I finally replaced the cap my problems went away.  I am still using the saw, bought new in 1983.

A few years ago I had ignition issues.  As it turned out it was the spark plug wire itself.  Replacement coils were not available.  I was ready to get a new saw.  At the last minute I discovered that the spark plug wire was NOT molded into the coil.  It actually "screwed" in.  I unscrewed the old wire, put in a new one and I am still running.

Doug in SW IA
I can't tell you how many people have thrown away spark coils just because the plug lead wire wasn't screwed in or the barb at the boot connection was corroded away.

Especially critical in older saws with parts NLA....check the plug lead at both ends!

Kevin