Stihl 036 wont rev

[Frank T]

Ive been reading this Forum for a while and finally got signed up and this is my first post!

I bought a used Stihl 036 a few days ago (not a PRO) and it will start and idle but as soon as I hit the throttle it sputters and dies. I set it on the choke setting and it starts right up again and will idle without any issues. I tried feathering the throttle but it still dies. IF it start it and hammer the throttle from the start, it will race for 3-4 seconds (sounds GREAT) then dies again. Then back to choke- 1 pull - start and idles.... But Ive yet to cut a piece of wood at Idle so this saw needs to run.

What Ive done so far:
Removed all the gas and added the mixture I use in my other saws - Stihl 025 & 039 (Stihl 2 cycle oil and 92 octane)
Added Stihl bar oil
Loosened the chain a little (Seemed to be jerky going around the bar)
Removed Air filter and cleaned it with my air hose (runs the same with our without the air filter on it)
Checked the plug and it has a good strong spark
Tested the compression at 100lbs (might be more since I didnt get a seal on the head - the threads on my tester were too long for the spark plug hole and it hit the piston, so I had to back out the threads until the piston was free to move)
Took the muffler off and the piston looks excellent and the rings are free
Choke plate works as it should
I worked on it for about an hour so the saw was warmed up

Im not sure why, but There is tape around the throttle handle to hold a thin switch down that pops upward out of the handle. my other saws have this also but Im not sure what that switch does.

Although Ive done just about anything you can do mechanically to a car in 20+ years (brakes, electrical, engine rebuilds, Rears rebuilt, etc) I dont know anything about small engines, so ANY suggestion will help me learn, even the most basic suggestion is welcome.

Thanks in advance
Frank T

[JohnG28]

Welcome to the forum.  Have you looked over the fuel lines, fuel filter? Could be a plugged pick up. Could also need a carb rebuild, which is pretty easy as well. It may not say pro on it but an 036 is a nice pro series saw.

[AdkStihl]

The switch you are referring to is called the operator presence lever. Really has nothing to do with why the saw wont run correctly........safely yes, but lets get the saw running.
You need to figure out what Make and Model carburetor is on the saw as there were several and report back here so we can accurately help you find a carburetor rebuild kit.
Once the carb is rebuilt, I suggest changing the fuel hose, fuel filter and impulse hose.

Fuel Hose PN# 1127 358 7702
Fuel Filter PN# 0000 350 3504

The impulse hose is a standard piece of fuel line (3/16 x 3/32 x 4" long)

[thecfarm]

Frank T,welcome to the forum.

[MidWestTree]

I always check the impulse hose first if it has one, some of them feed internally through a passage in the intake boot.

Often I find experienced engine guys from v-8's down to the common 4 cycle utility motors haven't run across that in a chainsaw yet but it's simply the engine's way of providing impulse to the diaphragm in the carburetor to move fuel

[Frank T]

First thanks for everyone's guidance and quick responses!

Here's what I found today...
Im not sure WHERE the impulse hose is, could someone post a picture so I know what Im looking for.

1. I pulled the fuel line and filter in the tank. The filter looked a little dirty but the fuel line looked pretty good. I blew it out with air just to make sure and reinstalled it. Result: still wouldnt throttle
2. I found a length of fuel line and ran it from the carb right into my fuel can. At first there was no change but then it seemed to work! Ran to my Stihl dealer and got a new filter but he did not have the hose. Used the old hose with the replaced the filter. Result: Wouldnt Throttle
Im guessing its the hose collapsing or the carb does not have enough vacuum to pull the fuel through the twists in the fuel line. So Im going to get a carb kit for it also, here are the numbers off the carb:
Cast in the side: C3A
Stamped on the side: S4C24J
Cast in the top: ZAMA Hong Kong
Stamped on the bottom: STIHL
Please let me know the part number for the carb or Carb kit... THANKS!

One thing I found odd. When I looked up the fuel line for the 036 it has a few different ones depending on the year.

The one on my saw looks like this:
http://www.ebay.com/itm/NEW-GAS-LINE-HOSE-FUEL-FILTER-FOR-STIHL-038-MS-380-EARLY-034-036-064-CHAINSAW-/141006148531?pt=LH_DefaultDomain_0&hash=item20d49f13b3

But it curves more like this one when its installed:
http://www.ebay.com/itm/NEW-FUEL-FILTER-FUEL-LINE-FITS-STIHL-029-039-034-036-MS390-MS290-13290-RT-/390676482472?pt=LH_DefaultDomain_0&hash=item5af62209a8

Any chance I have the wrong fuel line on it?

Thanks
Frank T

[ZeroJunk]

The line should work fine if it will seal where it goes through the tank wall. That is usually the difference. On some models they had a couple of different size openings, why I don't know.

You may just have a bugger in the high speed circuit in the carb. If it has carb limiters you will need to remove those to get the adjustment needles out to clean properly. Get a can of carb cleaner and use that, not compressed air, to clean out all the passage ways.

If the saw will sit and idle there is nothing serious wrong with it I wouldn't think.

[AdkStihl]

You need a ZAMA RB-31 carburetor rebuild kit

[Frank T]

Guys
Thanks for the info on the fuel line and part number for the carb kit. Ill be ordering a new fuel line and carb kit today. When I get it back together Ill post the results.

A buddy at work said he had a chainsaw that had a similar situation and found the vent on his gas cap was blocked. I had this issue with a 70 Mustang, but it took a long time to create a vacuum strong enough to over come the fuel pump suction. Since this happens almost instantly in my saw I dont think its a vacuum/venting issue but How does the fuel tank vent on a Stihl 036? Does the Impulse hose have something to do with it? Just trying to learn as much as I can while Im waiting for the parts.

Thanks
Frank T

[AdkStihl]

The tank vent has nothing to do with the impulse hose. The impulse hose feeds low pressure impulses from the crankcase to the carburetor to create a fuel "pumping" action...... more or less.
Throughout the life span of an 036/MS360 there were 4 different styles of tank vents. All 4 are located in the same place however. Inside the "air box", on the top left hand corner of the fuel tank.

[sharkey]

It could be something as simple as the carb adjustment or it could be more complex like a leaking crank seal or cylinder base gasket.  An 036 is a minimum of 10 years old.  The only way you will know if its leaking is to test it.  You can do it yourself or you can take it into the shop once its torn down and spend a couple bucks for them to do it.  If you choose to do it yourself use a brake bleeder to do the vacuum test.  Use a regulator on your compressor air line for the pressure test and dont go over 10psi.  Spray some soapy water around the seals and cylinder base (under pressure) and look for bubbles.  Do the same with the fuel line.  Once you get the intake off you will see the impulse hose.  Use rubber strips placed between the muffler and cylinder and carb and cylinder to act as seals for the tests .  Tighten the plug.  Test through the impulse hose.  Here is a video for guidance;   http://www.youtube.com/watch?v=radOV6rAJJU   

[sharkey]

Here is another vid on an older saw without any impulse hose.  Since you work on vehicles you may already have the Mity-Vac?  If not you can borrow a brake bleeder at the auto parts store.  Good seals/gaskets will hold 5 psi indefinitely.  Any pressure or vacuum changes occurring under a minute are suspect.  Turn the crank a little during the test to check for flat spots.  Again, your going to be looking at the crankcase half gaskets, the cylinder base gasket, and the crank seals.  Once you know the bottom end is sealed then you can move on to the next part.
  http://www.youtube.com/watch?v=jd8Pc7Rc1o4         

[clww]

Welcome to the Forestry Forum, Frank T.

[joe_indi]

AHEM, has anyone suggested that the H screw might be turned in to its stop?
If this happens the idle might work but the saw wont rev.
Try backing out the H screw 1 1/2 turns and try it from there.

Joe

P.S.
Welcome to the Forum

[AdkStihl]

AHEM, has anyone suggested that the H screw might be turned in to its stop?
If this happens the idle might work but the saw wont rev.
Try backing out the H screw 1 1/2 turns and try it from there.

Joe

P.S.
Welcome to the Forum

Read his post again Joe. He mentions it "races" for 3-4 seconds. If the jet was buried, it wouldn't race at all, it would just fall on its face no matter what you did. Remember, there are no limiters on that carb.

[Frank T]

Awesome stuff guys! Thanks for the suggestions.

Maybe I didnt make this clear above, but I got the saw running by using a fuel line I had laying around. I ran the fuel line from the carb to my container of fuel mix. It started and would rev normally, so I think the issue is the fuel line or the tank, since those were the items I eliminated during that test.

OK Here come the nubie 'I gotta know as much as I can' questions...

1.   What is the function of the 'H' Screw, how does it effect the saw and where is it located?
2.   Leaking crank seal or cylinder base gasket: why would there be pressure in the crank case or at the base of the cylinder and why is it important? Why is the cylinder pressure not contained on TOP of the cylinder? If the pressure is not at the top of the cylinder how does it blow the cylinder down when the charge ignites? Pressure in the crank case of a 4 cycle motor means the compression rings are bad or you have a leaky head or intake... all BAD news. I had a guy bring me a 68 Vette that would push the dipstick out of the tube about an inch when he revved it, That's serious crank case pressure.
3.   Does anyone have an exploded view of the 036 they can share with me showing all the parts (email: deedo773@msn.com) Or have a link to where I can get it? I checked the Stihl site but could only find the operational manual. That may help with a lot of questions when I dig into this further. I can already see the chain oiler is throwing a lot of oil, so that will be my next project on this saw.

Thanks
Frank T

[joe_indi]

-----------------------
Read his post again Joe. He mentions it "races" for 3-4 seconds. If the jet was buried, it wouldn't race at all, it would just fall on its face no matter what you did. Remember, there are no limiters on that carb.

"it will start and idle but as soon as I hit the throttle it sputters and dies. I set it on the choke setting and it starts right up again and will idle without any issues. I tried feathering the throttle but it still dies. IF it start it and hammer the throttle from the start, it will race for 3-4 seconds (sounds GREAT) then dies again."
I dont have a 036. But I have 9 spanking new MS360s plus one that I run once in a way to show my customers one great saw from Stihl.
I got the same symptoms when I turned in the H screw to its stop.
If you blip the throttle with the H screw closed it will start to rev a bit before dying out. That depends again on how much the L screw is turned out.
And, we never got them with limiter caps here.

[AdkStihl]

   Does anyone have an exploded view of the 036 they can share with me showing all the parts (email: deedo773@msn.com) Or have a link to where I can get it? I
Thanks
Frank T

(2) Emails sent

[AdkStihl]

These links might help you understand how a saw carb works. Pictures are worth.....1000.....chainsaws  ;)

http://www.zamacarb.com/index.html

http://www.walbro.com/techtipsmetering

http://www.tillotson.ie/techinfo-service.php

[ZeroJunk]

If you look in the barrel of the carb there will be one or two tiny holes in the barrel on the motor side of the butterfly. That is where your idle fuel comes in to the barrel to be mixed with air. It will be adjusted by the L or low needle which is closest to the motor. On the air filter side of the butterfly there is a brass nozzle that squirts in the high speed fuel. It is adjusted by the H or high speed needle which is furthest away from the motor. The idle mix gets air through whatever you have the butterfly cracked and there is often a little mouse hole in the butterfly to get air moving across the idle holes. Nothing can be pulled out of the high speed  nozzle until you open the butterfly, and then the high speed needle takes over.
A lot of the newer stuff has fixed jet and there is no high speed needle. And, most anything new has some kind of tamper proof deal to make it difficult to make adjustments.

[Frank T]

Guys Thanks for the info on the carb and the Exploded views! And The videos were very helpful in how to test, but Im still not sure WHY the pressure is needed. Can someone explain that? Again Im trying to understand as much as I can about these motors.  Thanks!!!

" 2.   Leaking crank seal or cylinder base gasket: why would there be pressure in the crank case or at the base of the cylinder and why is it important? Why is the cylinder pressure not contained on TOP of the cylinder? If the pressure is not at the top of the cylinder how does it blow the cylinder down when the charge ignites? Pressure in the crank case of a 4 cycle motor means the compression rings are bad or you have a leaky head or intake... all BAD news. I had a guy bring me a 68 Vette that would push the dipstick out of the tube about an inch when he revved it, That's serious crank case pressure."

[AdkStihl]

After TDC the piston travels downward......compressing air and gasses in the crank case.
As the piston reaches BDC, the upper transfers are exposed. Its at that moment, the pressurized gasses in the crankcase are then "transferred" to the combustion chamber.

2-Cycle 101

[joe_indi]

.............  why would there be pressure in the crank case or at the base of the cylinder and why is it important? Why is the cylinder pressure not contained on TOP of the cylinder? If the pressure is not at the top of the cylinder how does it blow the cylinder down when the charge ignites? Pressure in the crank case of a 4 cycle motor means the compression rings are bad or you have a leaky head or intake... all BAD news. I had a guy bring me a 68 Vette that would push the dipstick out of the tube about an inch when he revved it, That's serious crank case pressure.........

I dont know how far this is true, IMHO the 2 stroke engine is actually a 4 stroke engine.
It completes all four strokes in one rotation.
A 4 stroke engine uses only the upper part of the piston, cylinder and the cylinder head with its valves to complete the four strokes in 2 rotations.
In the 2 stroke engine two of the four strokes are handled by the lower parts of the piston and cylinder.The induction and compression stroke (the latter partially).
The combustion and exhaust strokes are handled by the upper parts of the piston and cylinder.
The job of the valves are done by the ports on the cylinder and piston.
This is why, unlike a true 4 stroke engine, the 2 stroke motor needs an air tight crankcase to do the job of induction and compression properly.
This is only my "home-made" theory, if the experts here consider its wrong, I stand corrected.

Joe

[ZeroJunk]

The fuel supply that the engine burns all comes through the crankcase and is then pushed through the transfers in to the combustion chamber.

The pressure test is not to mimic anything that is happening while the saw is running necessarily. I don't think running pressure ever goes over 5 pounds.  It is to make sure there are no leaks which will lean the saw out and burn it up.

[ancjr]

For what it's worth...  I had this same problem with my ms180 last week.  I took it in Friday, guy took the carb off, tested the fuel line, sprayed the carb with cleaner and put it back together.  I verified it ran fine before leaving. 

Head out Monday morning with it and it runs about 30 seconds before getting even worse.  This time, the saw quits almost like I hit the kill switch when I pull the trigger.

Back at the shop, the head tech takes the carb off and found the jets plugged.  Poked out the jets with a thin wire.  The fuel line held pressure fine, but showed a wet spot near the attachment of the fuel filter - a micro pin hole that would surely only get worse.  New fuel line, blast the jets out, reassemble and it ran fine all week.

Pretty sure it is fixed now.   8)