Stihl 046 Dies When Given Throttle

[ilinimud]

Hello all, I bought a Stihl 046 Magnum locally from a small engine guy kinda cheap, so assumed it would have some issues, and it does. I am brand new to taking apart and fixing saws, but so far i am really enjoying it. Hopefully some of you can help me with what i have going on.

Previous owner told me he had been using the saw a while, so he put new piston and rings in the saw for the sale of it, also a new muffler. When i got the saw it would rev very high but would eventually chill out, and run better. I attempted to tune it one day (with a tach), and things got worse. Upon looking over everything i shone a light in at the impulse line, and it was disconnected at the motor. I thought i had found the fix. Nope. After i reattached that i set the carb back to recommended settings, and started it up. It started great, as always, and didn't try to rev high and spin the chain like it was, BUT when i hit the throttle it dies. Every time. I then have to re choke it to get it to start, then once throttle is applied - dead. So i thought it has to be the fuel lines or carb, and i need to build up some parts i thought, so i ordered a new carb too. Slapped those puppies on there. No change.

So i was a good boy and listened to everyone here and left it the hell alone until i got my pressure/vacuum tester. Finally got the ports blocked and the test finished tonight, and to my surprise it held both. I did spray some Simple Green on the seals, etc and on the clutch side in one tiny area i had some bubbles, but the gauge held for many minutes. Spun the flywheel around and the gauge fluttered. Moved the saw around with no change on gauge. I could not spray the flywheel side seals because i cannot get it broke loose with a hammer and punch with heat and prying assistance. I have a Stihl puller coming for that. While i was on that side of things i got thinking about the ignition module/electronics (knowing nothing about it at all) i found a small patch of bare wire on the inside of the case. Could this cause this issue? Also i noticed while trying to remove the flywheel that certain spots of it seem to not have any magnetism at all. Only one real strong spot on it.

Sorry for the long post, but this one has been a battle, and i want to learn how to fix these great old saws. I'm attaching a picture of the wiring harness.

 

[Woodslasher]

Hello all, I bought a Stihl 046 Magnum locally from a small engine guy kinda cheap, so assumed it would have some issues, and it does. I am brand new to taking apart and fixing saws, but so far i am really enjoying it. Hopefully some of you can help me with what i have going on.

Previous owner told me he had been using the saw a while, so he put new piston and rings in the saw for the sale of it, also a new muffler. When i got the saw it would rev very high but would eventually chill out, and run better. I attempted to tune it one day (with a tach), and things got worse. Upon looking over everything i shone a light in at the impulse line, and it was disconnected at the motor. I thought i had found the fix. Nope. After i reattached that i set the carb back to recommended settings, and started it up. It started great, as always, and didn't try to rev high and spin the chain like it was, BUT when i hit the throttle it dies. Every time. I then have to re choke it to get it to start, then once throttle is applied - dead. So i thought it has to be the fuel lines or carb, and i need to build up some parts i thought, so i ordered a new carb too. Slapped those puppies on there. No change.

So i was a good boy and listened to everyone here and left it the hell alone until i got my pressure/vacuum tester. Finally got the ports blocked and the test finished tonight, and to my surprise it held both. I did spray some Simple Green on the seals, etc and on the clutch side in one tiny area i had some bubbles, but the gauge held for many minutes. Spun the flywheel around and the gauge fluttered. Moved the saw around with no change on gauge. I could not spray the flywheel side seals because i cannot get it broke loose with a hammer and punch with heat and prying assistance. I have a Stihl puller coming for that. While i was on that side of things i got thinking about the ignition module/electronics (knowing nothing about it at all) i found a small patch of bare wire on the inside of the case. Could this cause this issue? Also i noticed while trying to remove the flywheel that certain spots of it seem to not have any magnetism at all. Only one real strong spot on it.

Sorry for the long post, but this one has been a battle, and i want to learn how to fix these great old saws. I'm attaching a picture of the wiring harness.


View attachment 893278

I'm not a pro, but I'll try to answer your questions as best as I can. First and foremost, does it have an oem piston/rings or aftermarket? Second, does it act like someone hit the kill switch and just die or does it bog down and die? Also, did you get an oem carb/fuel line or aftermarket ones and did you replace the impulse hose? When you say there were some tiny bubbles, were they from the case gasket or the clutch side seal? If they were from the seal I'd replace it as it's cheap and easy to do. The bare wire is a problem and I'd definitely replace it before buying any more parts, but I'm not convinced it's your problem. Finally, the flywheel is only supposed to have one spot that is magnetic, look at an aluminum one and you'll see what I mean. The plastic flywheel confused me too when I first ran across them.

 

[SteveSr]

I'm attaching a picture of the wiring harness.

That yellow wire is the kill wire. If it grounds out then no spark...

 

[drf255]

I’ll take a shot at it.

How does the piston look? Does it feel like it’s got good compression?

Did you change the spark plug and inspect the lead to the plug for any breaks? Is the coil that grips the plug electrode inside the boot?

As for the wires, tape them. I’m fairly certain that the black is the kill wire to the coil and the yellow has a ringlet at the end to ground out to the case, so the yellow wire grounding won’t do anything.

Did you use aftermarket parts? How did you vac test? Did you plug the decomp? Did you inspect the intake boot? Does it have proper clamp, and inner and outer surround inside the carb box? Is the boot OEM? I’ve heard of AM boots actually sucking closed when warmed up and throttle hit.

Let us know.

 

[pioneerguy600]

On the 1128 series saws the black wire runs from the module to the switch, the yellow with stripe runs back from the switch to ground. With the yellow wire already grounded it would not kill spark unless the switch is closed.

 

[SteveSr]

As for the wires, tape them. I’m fairly certain that the black is the kill wire to the coil and the yellow has a ringlet at the end to ground out to the case, so the yellow wire grounding won’t do anything.

You may be correct. I just got done with some other brand saws and the yellow was the kill wire. The truth will be told by whatever color wire is coming off of the kill terminal on the coil or attached to the moving part (not spring) on the master control lever.

 

[ilinimud]

Alight so i have a small update, and still no success. So i needed a new fuel tank anyway because the front plastic where the AV mount is was broken, and rigged up. Bonus was that it came with a new wiring harness. I got everything put back together tonight, and have no spark at all now. So i guess it has actually gotten a step worse haha. Im really at a loss with what to do. I am not that good with a voltmeter, but it seems like thats the next step?

To answer some earlier questions about the vac test: I blocked off the intake with a rubber plug and zip strip, and they connected straight into the impulse line with the tester. The intake boot is actually OEM. It seems to be all OEM, maybe the piston could be aftermarket. I didnt take the cylinder off, just looked through all its holes. Piston looks great, cylinder too. The tiny bubbles i got on the pressure test were from seal on the clutch side.

 

[Woodslasher]

Alight so i have a small update, and still no success. So i needed a new fuel tank anyway because the front plastic where the AV mount is was broken, and rigged up. Bonus was that it came with a new wiring harness. I got everything put back together tonight, and have no spark at all now. So i guess it has actually gotten a step worse haha. I'm really at a loss with what to do. I am not that good with a voltmeter, but it seems like that's the next step?

To answer some earlier questions about the vac test: I blocked off the intake with a rubber plug and zip strip, and they connected straight into the impulse line with the tester. The intake boot is actually OEM. It seems to be all OEM, maybe the piston could be aftermarket. I didn't take the cylinder off, just looked through all its holes. Piston looks great, cylinder too. The tiny bubbles i got on the pressure test were from seal on the clutch side.

If you now have no spark, something in the wiring harness is probably messed up or hooked up wrong and since the clutch side seal leaked, I'd replace it because it's cheap insurance. If everything with the wiring harness looks ok, disconnect everything but the plug wire from the coil and see if you get spark. If you do get spark, something in the harness is wrong. If you don't, your coil is bad. I just went through a similar process on a 461, in my case the coil had died.

 

[ilinimud]

The new tank also came with a new killswitch, so i put the oem one back in, and BAM, engine hit. Took off choke and started, it stuttered and died. When i try to re start i can pull all day long and nothing unitl i re choke it. RE apply choke, hits, remove choke, runs while i feather the throttle kinda now but sounds and smells awful. Smells like a 4 stroke engine running almost if that makes sense. My original fix for the problem was to replace the carb, and thats whats in it now. A new Farmertec carb.

i have it adjusted to 1 1/2 turns out L - 1 Turn out H - LA is sitting on the throttle plate.

 

[Woodslasher]

A/M carbs are an unknown realm for me, but I'd try 1 turn out for H and L. The way to initially set the LA is to turn the screw in until you can see the back butterfly loose open up a little, then fire up the saw and turn the LA out until it is able to idle on its own. Once it's warmed up, turn the LA in until the chain stops spinning and the saw starts sounding like it might die. For mixture tuning, I haven't mastered that yet so I can't give any advice with that.

 

[Woodslasher]

Double post.

 

[ilinimud]

Threw the previous carb on it, and its a little worse with it. Tried 1 turn each on it. Turned up the LA some too. That seemed to just make it rev slightly higher before it dies. Maybe tomorrow I'll have better luck.

 

[Woodslasher]

Threw the previous carb on it, and its a little worse with it. Tried 1 turn each on it. Turned up the LA some too. That seemed to just make it rev slightly higher before it dies. Maybe tomorrow I'll have better luck.

That sounds like an air leak to me. I'd replace the clutch side seal and check the fuel level in the tank before going any further. A nearly-empty tank will cause just that and will seem like an air leak. Ask me how I figured that one out....

 

[ilinimud]

It held vacuum and pressure for a long as i would keep it hooked up, moving the saw around as well. There were like a few single bubbles coming from the seal. Seams like that isn’t enough to effect the saw. Oh well, need the practice on seal swapping anyway.

Tank is full also. Thanks for throwing out help, I’m totally teaching myself through forums and service manuals with no help from actual people in person. Kinda tough.

 

[huskihl]

Turn your H and L screw out another half turn and try it again

 

[ilinimud]

Holy cow man. Adjusted the carb another half turn this morning, and we have a running 046 now. Im sure the war isnt won yet, but i sure feel a lot better now! I had messed with the carb many times before. Something i did was the magic combo though. Next up, getting my DCS 6401 to run. Thanks for all the help.

 

[SteveSr]

Holy cow man. Adjusted the carb another half turn this morning, and we have a running 046 now. Im sure the war isnt won yet, but i sure feel a lot better now! I had messed with the carb many times before. Something i did was the magic combo though. Next up, getting my DCS 6401 to run. Thanks for all the help.

Take your original OEM carb and put an OEM (Walbro, Zama) kit in it. That 046 is old enough to have stiff diaphragms in it. If it is an unmodified saw it should run pretty well at the stock carb settings of 1 & 1 (assuming a carb with no limiter cap design).

 

[WeenerDog]

I ran into an issue last week where it ran great for a minute then died until primed again, and choked. Pressure / vac test was perfect; fuel system held pressure. Turns out the (new) impulse hose had a kink in it after re-assembly, etc. I think it was cut a bit long out of generousity -- Stihl is charging $11/foot for the good stuff...