Stihl 034 super not getting fuel?

[CrespyCream]

Hi everyone first post here, wish it was under better circumstances! I recently acquired a 034 super and i’m at my wits end with it. The dang thing just will not run no matter what I try and I feel that i’ve exhausted my options I know of.

For starters the thing looks great, fresh rubber all the way around (OEM) so no air leak that I could find. I’ve verified strong spark with a new plug, threw a new fuel line, filter, tank vent, and 2 different carburetors at it and still no luck. Piston looks great too, no scoring or concerning marks visible on intake or exhaust side.

I’m very suspicious that it’s simply not getting enough fuel. The impulse line is not cracked but i’m wondering if the fitting might be gunked up? I tried getting a small wire in there and pressing around but still no luck. Anyways the carb does have fuel in it if i take it apart but I did notice that if i remove the fuel line to the carb no fuel comes shooting out like all my other saws do. However if i unscrew the cap, blow in it then reseal the cap fuel will come spraying out of the line.

If i try and start it for a while then remove the plug, it is very slightly moist not soaking wet like a flooded saw would be. I’m very comfortable tuning my saws, and messing with that has also not worked. However if i pour a little fuel in the cylinder it will want to fire up right away with only a pull or two. I really am thinking it’s just not getting enough fuel inside the cylinder but I am absolutely stumped on why that is!

 

[lone wolf]

Hi everyone first post here, wish it was under better circumstances! I recently acquired a 034 super and i’m at my wits end with it. The dang thing just will not run no matter what I try and I feel that i’ve exhausted my options I know of.

For starters the thing looks great, fresh rubber all the way around (OEM) so no air leak that I could find. I’ve verified strong spark with a new plug, threw a new fuel line, filter, tank vent, and 2 different carburetors at it and still no luck. Piston looks great too, no scoring or concerning marks visible on intake or exhaust side.

I’m very suspicious that it’s simply not getting enough fuel. The impulse line is not cracked but i’m wondering if the fitting might be gunked up? I tried getting a small wire in there and pressing around but still no luck. Anyways the carb does have fuel in it if i take it apart but I did notice that if i remove the fuel line to the carb no fuel comes shooting out like all my other saws do. However if i unscrew the cap, blow in it then reseal the cap fuel will come spraying out of the line.

If i try and start it for a while then remove the plug, it is very slightly moist not soaking wet like a flooded saw would be. I’m very comfortable tuning my saws, and messing with that has also not worked. However if i pour a little fuel in the cylinder it will want to fire up right away with only a pull or two. I really am thinking it’s just not getting enough fuel inside the cylinder but I am absolutely stumped on why that is!

So when it fires on fuel dumped in manually, does it run or die?
How is the spark looking?

 

[CrespyCream]

So when it fires on fuel dumped in manually, does it run or die?
How is the spark looking?

With fuel dumped in it will “pop” and try to run but will not stay running for more than a few second or so.

 

[lone wolf]

With fuel dumped in it will “pop” and try to run but will not stay running for more than a few second or so.

How's the spark look?
Was it pressure and vac tested?

 

[Old2stroke]

Are you saying that if you try to start it with the choke fully on (closed) and the carb set to fast idle it won't even fire, yet the plug says it is getting fuel (slightly moist?), however, if you squirt fuel into the carb throat, it will fire and use up the fuel you squirted in? Starting is all about the choke being FULLY closed and the throttle partly/fully open. Actual running after starting is all about the impulse from the crankcase operating the fuel pump in the carb. You can test the impulse by hooking a vacuum gauge to the line and pulling the engine over, the gauge should bounce both sides of zero. Can also get a drop of oil in the line and see it move up and down as the engine is turned over.

 

[Bob Hedgecutter]

Correct air fuel mix, compression, spark and TIMING of that spark is pretty much all you need.
So, by the wet plug, we can judge it is getting some form of fuel to the combustible zone- you have verified strong blue spark on the new plug fitted- at this stage we are assuming good compression by the looks of the piston through the exhaust port- cylinder has not been off to check broken rings or heat seize rh side of the piston away from the lean/straight gas giveaway of the exhaust port.
Also assuming the cylinder is air tight......... pressure test and you can eliminate that- or guess.

So, how does the saw hang on the pull start handle? Roll down quick with a rapid chuff chuff chuff- or slowly with a thunk........ thunk.........

Next port of call is that timing part- really need to pull the flywheel and check the key is not shorn and the flywheel out of kilter with the crank.
You saw it has had all fresh rubberware done- done by you? Were the main crank seals done as well? This is a good reason for checking- if the nut on the crank was a little loose- if the key was left out of the keyway, or the flywheel sheared it- the timing could be all to crap, you can have strong spark and fuel/air delivery spot on, but if it is sparking closer to BDC than TDC.......... no go.

 

[L34]

Bright blue spark one thing.
Bright blue spark under compression another.
Has this happen with an 064.
Replaced plug and all good.

 

[pioneerguy600]

On the 034`s I have had many in that had this problem, the impulse line connection at the crankcase was loose and not enough impulse signal was getting to the carb. There were no cracks in the impulse line but the line was stretched/expanded too much at the barb on the crankcase connection. Only use OEM lines on these saws as most anything else I have tried failed shortly after, fuel line just won`t stand up to the heat the crankcase transfers to the line.

 

[stihltech]

Just check that you have a fast idle. The throttle should be held slightly open when on choke and the fast idle setting. The saw may not start without it.
Common issue. The fast idle detent on the master shaft breaks off.
If OK, take heed of everything else mentioned. The vacuum and pressure test is a must, especially on a saw over 20 years old. (Maybe 30),

 

[CrespyCream]

Thank you all for the replies and sorry for my late reply, work has been keeping me busy lol.

Just an update, the saw has a new spark plug getting a nice spark to it. Additionally while the saw has not been pressure tested (don’t have the tools unfortunately) I did do a “redneck” compression test and put a small amount of oil in the cylinder. Lo and behold the saw fired right up and ran for a short amount of time until the oil burned off.

I was able to borrow a compression tester to do it the proper way and 135 psi came back as the most consistent result. However i’m wondering if there is some left over residual oil that pushed that number up a little bit. In the mean time i’ll check the impulse line and a couple other items you guys have suggested and report back