031av nonstart after repairs

[Tait]

I pulled my dad's late 70's 031av out of the shed to go to work. It has sat for a few years (empty) as I could not get it started. I figured I would get to it at some point. That time has come. Here is what I have replaced:

Rebuilt the Walbro carb (diaphragm was stiff so assumed that was the problem)
Reset high and low to 1 1/4 turns out
New fuel line from white elbow to carb
Checked impulse line and carb boot for cracks. None found
New spark plug
Pulled condenser and replaced with electronic ignition module

The saw shows the same condition as before. It will NOT start up. If I shoot a squirt of starting fluid it will fire up for a half second, but once the starting fluid flashes off then nothing. I pulled the spark plug and have spark. Also put a spark plug tester on and it too sparks. Checked the compression. It came in at 115 psi. I am assuming this is low? The spark plug hole has been coiled. Way before my time and I doubt my dad would remember when it was done.

At this point, I have a new impulse line and good used carb boot in case either of those have slight leaks. I need to get out my multimeter and check the coil for proper resistance. I need to see if I can find that number on here somewhere. Does anyone have any ideas what else could be the issue?

My next steps:

Pull coil and test
Replace piston and rings

I know I am putting a lot of effort into an older and outdated saw but it has sentimental value and I would love to get it running and cutting again. Thanks.

 

[mmzullo]

Well I will try to help. I just rebuilt my carb on an 030av. I replace fuel hoses and filter rebuilt carb(tillonston) I think I spelled it right. Compression was 125. But it ran fine last year and wouldn't start this year. It would run if I put gas in the carb. But any way. When I rebuilt the carb I set the needle valve too low and it would not get fuel. Make sure the carb has fuel at the diaphragm if you take it apart. I then had it set too much fuel. It would run but flood. I would use gas to jump start it with instead of either.
But I would start there. Good luck

 

[HarleyT]

I pulled my dad's late 70's 031av out of the shed to go to work. It has sat for a few years (empty) as I could not get it started. I figured I would get to it at some point. That time has come. Here is what I have replaced:

Rebuilt the Walbro carb (diaphragm was stiff so assumed that was the problem)
Reset high and low to 1 1/4 turns out
New fuel line from white elbow to carb
Checked impulse line and carb boot for cracks. None found
New spark plug
Pulled condenser and replaced with electronic ignition module

The saw shows the same condition as before. It will NOT start up. If I shoot a squirt of starting fluid it will fire up for a half second, but once the starting fluid flashes off then nothing. I pulled the spark plug and have spark. Also put a spark plug tester on and it too sparks. Checked the compression. It came in at 115 psi. I am assuming this is low? The spark plug hole has been coiled. Way before my time and I doubt my dad would remember when it was done.

At this point, I have a new impulse line and good used carb boot in case either of those have slight leaks. I need to get out my multimeter and check the coil for proper resistance. I need to see if I can find that number on here somewhere. Does anyone have any ideas what else could be the issue?

My next steps:

Pull coil and test
Replace piston and rings

I know I am putting a lot of effort into an older and outdated saw but it has sentimental value and I would love to get it running and cutting again. Thanks.

If it runs only for 1/2 of a second, then something is wrong. Likely ignition timing is not right for starters.
There maybe carb issues as well. But it should roar to life and run for several seconds or more after a prime/squirt.

 

[burnses]

the 031 series has such a following that seem to really capture what older"historic" or vintage saws are all about...they have a personal connection and a history of some kind...my dads saw we cut wood together ....gradpas saw whatever "used to cut a bunch of wood with that saw"......but more than any other vintage stihl they can really frustrate the hell out of ya! And you though I would tell ya what the problem is.....

good luck there fun...sometimes!

well ill bite!...I would do a vacume ck on the fuel hose...pull the filter off and plug the end of the hose use a mity vac or the like to suck on the other end of the hose if it dosent hold vac then there is a hole and fuel cant get sucked to the carb...think bout a 31 is the fuel gets pulled up to the top of the tank then down to the carb....if that hose is soft or has a leek difficult for fuel to get to the carb...

 

[Tait]

Well I will try to help. I just rebuilt my carb on an 030av. I replace fuel hoses and filter rebuilt carb(tillonston) I think I spelled it right. Compression was 125. But it ran fine last year and wouldn't start this year. It would run if I put gas in the carb. But any way. When I rebuilt the carb I set the needle valve too low and it would not get fuel. Make sure the carb has fuel at the diaphragm if you take it apart. I then had it set too much fuel. It would run but flood. I would use gas to jump start it with instead of either.
But I would start there. Good luck

I am going to try pouring a little gas in the cylinder to see if it fires up for a few seconds. I have the carb set to factory specs so hopefully that gets me started. Thanks

 

[Tait]

If it runs only for 1/2 of a second, then something is wrong. Likely ignition timing is not right for starters.
There maybe carb issues as well. But it should roar to life and run for several seconds or more after a prime/squirt.

I just checked and think the card I used to set the magneto gap was too thick. Actually used my shims this time and set it to 0.080 (right in the middle of what it should be). It is too late here to try to start it so it will have to wait until tomorrow evening when I get home from work.

 

[Tait]

the 031 series has such a following that seem to really capture what older"historic" or vintage saws are all about...they have a personal connection and a history of some kind...my dads saw we cut wood together ....gradpas saw whatever "used to cut a bunch of wood with that saw"......but more than any other vintage stihl they can really frustrate the hell out of ya! And you though I would tell ya what the problem is.....

good luck there fun...sometimes!

well ill bite!...I would do a vacume ck on the fuel hose...pull the filter off and plug the end of the hose use a mity vac or the like to suck on the other end of the hose if it dosent hold vac then there is a hole and fuel cant get sucked to the carb...think bout a 31 is the fuel gets pulled up to the top of the tank then down to the carb....if that hose is soft or has a leek difficult for fuel to get to the carb...

I have a few others that run so this is just a "let me see if I can get it going again" project. This one is starting to frustrate me to no end. I peeked into the cylinder through the spark plug hole and it looks good. No apparent scaring or scratches. I got out the Mityvac and tested from the fuel filter end to the line that ends at the carb. It held a vacuum with no problem. From what I can tell, all that is good to go then. I did put a new fuel filter on just to be sure.

The one thing that may be causing a fuel problem is the fuel cap. I assume that should be allowing air into the tank? Otherwise the carb would be pulling against a vacuum as there is no breather hose on this tank. I could not blow air through the small breather hole in the gas cap. Could that be the issue? Thanks.

 

[Phil_C]

Rebuilt the Walbro carb (diaphragm was stiff so assumed that was the problem)

I hate to state the obvious but did you make sure the needle valve is seated in the control lever correctly and/or stuck in its seat? As this saw has been sitting for a while did you remove the jets and make sure the ports are not blocked? Also there is a small mesh filter inside the carby that can block as well.

115 psi is low but I have a brushcutter with 106 psi that runs fine although obviously it lacks power. If you don't use the right compression tester you will get lower results.

 

[mmzullo]

Did you put the new fuel line in the tank ? The 030 I had had a real soft fuel hose that would collapse as you pulled a vacuum.

 

[Tait]

I hate to state the obvious but did you make sure the needle valve is seated in the control lever correctly and/or stuck in its seat? As this saw has been sitting for a while did you remove the jets and make sure the ports are not blocked? Also there is a small mesh filter inside the carby that can block as well.

115 psi is low but I have a brushcutter with 106 psi that runs fine although obviously it lacks power. If you don't use the right compression tester you will get lower results.

Please state the obvious. I am sure I am missing something. The needle vale was seated correctly and rose with slight pressure on the control arm. I pulled both jets and gave several good squirts of carb cleaner and air through the openings. All ports that I sprayed carb cleaner through showed nice strong sprays. I also replace the small mesh screen (the one that is about the same circumference as a pea. I may take it to the local shop and have them check the pressure. I appreciate the advice.

 

[Tait]

Did you put the new fuel line in the tank ? The 030 I had had a real soft fuel hose that would collapse as you pulled a vacuum.

The fuel line in the tank is not leaking, but I did just replace the fuel filter in case that was blocked enough to cause the fuel line to collapse. Hopefully she fires up tonight. I am thinking the gas cap is not venting, thus starving the carb. Will be trying to start it with the cap partially unscrewed to allow plenty of air in. Thanks

 

[HarleyT]

If it only runs for 1/2 of a second, then something isn't right. A saw with a fuel problem only will rev and run for several seconds or more on a shot of fuel in the carb, until the fuel is burned off.

 

[Phil_C]

Please state the obvious. I am sure I am missing something. The needle vale was seated correctly and rose with slight pressure on the control arm. I pulled both jets and gave several good squirts of carb cleaner and air through the openings. All ports that I sprayed carb cleaner through showed nice strong sprays. I also replace the small mesh screen (the one that is about the same circumference as a pea. I may take it to the local shop and have them check the pressure. I appreciate the advice.

That sounds fine. I have seen it before where the prongs that the needle sits in are on top of the needle instead of in the groove. I have also seen the little needle stuck and the diaphragm is unable to unseat it. Another thing you might want to check is the pump diaprahm is on the correct side of the gaskets. If it is on the wrong side then the valves wont work correctly.

I am thinking the gas cap is not venting, thus starving the carb.

Even if the tank vent was blocked it still should run for a few minutes until it starves of fuel. An easy test if you are unconvinced is to leave the cap loose slightly and start the saw on the ground. The fuel cap is on the top of the saw so no fuel should leak out. Don't forget to re-tighten the lid when done though

 

[Tait]

That sounds fine. I have seen it before where the prongs that the needle sits in are on top of the needle instead of in the groove. I have also seen the little needle stuck and the diaphragm is unable to unseat it. Another thing you might want to check is the pump diaprahm is on the correct side of the gaskets. If it is on the wrong side then the valves wont work correctly.



Even if the tank vent was blocked it still should run for a few minutes until it starves of fuel. An easy test if you are unconvinced is to leave the cap loose slightly and start the saw on the ground. The fuel cap is on the top of the saw so no fuel should leak out. Don't forget to re-tighten the lid when done though

Got home and tried a few things. I did tighten the gap between the magneto and flywheel to factory specs. Still no dice. I removed the spark plug and poured a teaspoon of gas in the cylinder. It fired up for a second, maybe a bit more but not much. So, she is sparking at least. I loosened the fuel cap just to see. Still would not fire up. The fuel line running into the carb is bone dry, after it running and being cranked with and without the choke on. The carb is not pulling fuel. I am going to pull the carb again, tear it down and triple check all the passages for good carb cleaner and air flow. I remember checking the diaphram to make sure it was right, but it cannot hurt to check it again. I remember one side the gasket is against the body and the other side it is not. I think the diphram side has the gasket against the body so the diaphram is away. I will also check the needle to make sure it is not sticking. I ordered a good used elbow and new impulse line to swap them out in case they fail a vacuum test. More to come. Thanks again. I appreciate all the help.

 

[HarleyT]

Probably one of your main problems...



And the timing thereof..........

 

[mmzullo]

Where did you set the needle valve arm? In my tillonston manual,it said flush with the lower bowl. It didn't want to run. I raised it like .010 just above the floor and it ran and runs good. Just double check that adjustment. Not sure about your carb setting.
But your on the right track with a fuel problem and not a spark problem. Unless the timing is way off

 

[HarleyT]

But your on the right track with a fuel problem and not a spark problem. Unless the timing is way off

mmmmmm..

 

[a. palmer jr.]

The 031 Stihl needs the timing set or the use of a flywheel made for electronic ignition. I'd bet that you can take the flywheel key out and advance the flywheel about an inch (measured from the outside edge) then tighten the nut real tight it would probably run. For some reason the 031 electronic chip, at least some of them is not a bolt in. I've used a timing light on these saws and noticed that the timing is actually after top dead center, so they need to have the timing set..

 

[HarleyT]

Unless the timing is way off

mmmmmmm. might at least consider it.........

 

[HarleyT]

But your on the right track with a fuel problem and not a spark problem. Unless the timing is way off

Or "you're"....

http://www.wikihow.com/Use-You're-and-Your