Stihl 031 wont start

[031av]

Hi all,

This is my first post on this forum and i have a technical question about my old Stihl 031AV chainsaw.
The problem is that there isn't comming any fuel into the cilinder, sparkplug stays dry. I noticed when i pull the cord there is fuel comming out of the airfilter. Compression is ok. When i put some fuel directly into the cilinder trough the sparkplug hole it also wont start. Spark plug is working fine.
I started to take apart the carberator and cleaned it and placed new gaskets. Now the problem is that there isn't comming any fuel into the carberator after i put it back together. But when i remove the airfilter and hold my finger against the air intake of the carb then it begins to suck fuel into it but still not into the cilinder. Stays dry frome some reason.

Does anyone know what to do or what i might have done wrong? I'd love to see my old saw back running.

Btw i'm from the netherlands so my english is not perfect i hope you guys understand what i'm trying to ask, otherwise please let me know.

[lone wolf]

Check the order of things in the carb with a parts diagram. What make and model carb is it?
Does the saw have good compression?
Is the choke operating?
Try cleaning the plug .

[031av]

Yeah i checked the diagram and i placed everything in the right order, except one thing is missing but it was never there, also not last year when the saw was able to start, so i dont know if its essential. I mean this part, nr 19 i guess its the piston chamber diaphragm:



Its a Walbro dont know which type exactly.

Also i replaced the old fuel with some new by the way.

Compression is good. Choke is operating but i wonder if its neccesary to have the choke being closed to create vacuum, i guess not? Because when i hold my finger against it (so without the airfilter) i feel vacuum and the fuel is moving through the hose when i pull the cord.

Also tried different sparkplugs.

[lone wolf]

You need to see if 19 is needed or if it is for a different model.

[031av]

When i look at the picture it seems to be exactly the same model, i got it from my dealer. He could order parts for this one or a Tillotson, according to my saw a 78 Stihl 031AV, he looked it up at the computer.

The gaskets i replaced are 18,22 and 25.

Or should a by a carberator kit from Ebay? Maybe that's a better idea because it has all the diapgram's etc also,  but a few gaskets and stuff are shown which i dont have so thats strange, maybe thats because its universal?. I'm talking about a kit like this:
http://www.ebay.com/itm/Walbro-K10-WAT-Carburetor-Carb-Repair-Kit-Stihl-028AV-031AV-032-032AV-Chainsaw-/181199223394?pt=US_Outdoor_Power_Equipment&hash=item2a3050ba62

That whole kit costs almost the same as one diaphragm would cost me from the dealer  :D

[AdkStihl]

That kit is universal for the WA & WT models. There will be extra diaphragms.

I've never owned a STIHL that would start without choke

[lone wolf]

Where is the choke in the filter or carb? He said the filter is off I only see one shaft on the diagram I assume the choke is in the filter?

[cornbinder]

google (stihl 031) this will get you to a list of webs. should be the 4th one down the list. puts you on the stihl web site and you can download the manual for your 031av

[031av]

Where is the choke in the filter or carb? He said the filter is off I only see one shaft on the diagram I assume the choke is in the filter?

Choke is in the airfilter.

But the strange thing is that even of i manage to get fuel to the carb, the fuell still wont go into the cylinder but leaves through the backside of the carb. And when i manually put some fuel into the cyl it also wont start though it has a spark.

Can it have anything to do with something other then the carb?

[lone wolf]

Yes it could be an air leak. The connection boot or mount to the carb for one. Then the impulse line then the crank seals. Do you try to start the saw with the filter on or off? Is the choke actually closing good?

[031av]

Carb mount is not leaking. I will try to check the crank seals. What do you mean by connection boot?

Tried it with the filter both on and off. And the choke is closing properly.

[lone wolf]

Where the carb mounts some saws use a boot that one may not i dont know just check for leaks. A vac test of the carb at the gas line would help eliminate some things then the saw. You can only check the crank bearings without a vac tester if there is up and down play the seals could leak. Best to vac test that saw.

[031av]

Allright checked the seals and don't seem to be leaking any oil so im trying to find out what else may cause an air leak.
Maybe i can try to find someone who can perform a vacuum test.
Otherwise i will order a walbro carb kit on Ebay to make sure the carb is 100%

[joe_indi]

..................
And when i manually put some fuel into the cyl it also wont start though it has a spark.

Can it have anything to do with something other then the carb?

The spark should ignite the fuel when you say the compression is okay.
The only reason  in the circumstance is that the plug is not sparking at the right point of time, probably from a bad flywheel key.
You will need to check this.

Joe

[sablatnic]

Try to take off the muffler, and look at the side of the piston. And try to start it without the muffler, the muffler could be clogged.

[031av]

A few weeks later now, At first i thought the compression was ok but seemed the pistonrings where a litte damaged.

Now i managed to get it started after i replaced the piston rings and piston pin bearing. It has more compression now and the sparkplug gets wet.

I was able to let it idle for minute or so.
But suddenly it stalled and now i cant get it running again.. >:(Disambled everything, checked piston rings etc all ok. cleaned carb and tightened every bolt but still wont start.
Sparkplug still is wet and there is a spark so that is not the issue. But now there is also leaking fuel out of the carb through airfilter side.  Anyone have an idea about where to look? I think its the carb but i already cleaned it. Maybe carb revision kit?