Stihl MS192TC Fuel Problems?

[Moto Mike]

I recently got a pretty great deal on an Stihl MS192TC. I checked it out before purchase, it started a little difficult, had a dull chain, but when running it pulled pretty good, oiled the chain well, and cut a lot and for a good price I was off to the races... for parts.

The saw likes to run with a bit of choke, but only for a little while and I'm not confident in tuning it until i get it to at least keep running consistently. It cuts out nearly constantly as if it is running out of fuel, it will idle but immediately bog if you try to give it gas or if you get it to rev it will stall out swiftly frequently. I did a bit more testing and it SEEMS that if I keep priming the primer bulb it keeps running fine and I can cut a 2" branch between bouts of priming, but it really seems like the saw is having a hard time pulling fuel from the tank and when I pump the primer bulb it never seems to fill, the bulb always has that bubbly feel like it's mixed air and water. I took a brief look at the fuel lines and they appear okay and are flexible not dried out and stiff or anything but it's a totally new fuel layout to me and I'm unfamiliar with the saw and 2 strokes in general. Anybody who has had this issue or can point me in the right direction would be much appreciated. I don't want to tear down the whole saw trying to find a cracked something somewhere if there's an obvious common answer and specific thing I need to buy. Thanks in advance!

 

[Tobystihl]

I recently got a pretty great deal on an Stihl MS192TC. I checked it out before purchase, it started a little difficult, had a dull chain, but when running it pulled pretty good, oiled the chain well, and cut a lot and for a good price I was off to the races... for parts.

The saw likes to run with a bit of choke, but only for a little while and I'm not confident in tuning it until i get it to at least keep running consistently. It cuts out nearly constantly as if it is running out of fuel, it will idle but immediately bog if you try to give it gas or if you get it to rev it will stall out swiftly frequently. I did a bit more testing and it SEEMS that if I keep priming the primer bulb it keeps running fine and I can cut a 2" branch between bouts of priming, but it really seems like the saw is having a hard time pulling fuel from the tank and when I pump the primer bulb it never seems to fill, the bulb always has that bubbly feel like it's mixed air and water. I took a brief look at the fuel lines and they appear okay and are flexible not dried out and stiff or anything but it's a totally new fuel layout to me and I'm unfamiliar with the saw and 2 strokes in general. Anybody who has had this issue or can point me in the right direction would be much appreciated. I don't want to tear down the whole saw trying to find a cracked something somewhere if there's an obvious common answer and specific thing I need to buy. Thanks in advance!

Sounds like it needs a carb kit, diaphragms are probably hardened and not pumping fuel.

 

[Moto Mike]

Sounds like it needs a carb kit, diaphragms are probably hardened and not pumping fuel.

I'm not too familiar with 2 stroke carbs, though I've pulled a few week wacker ones apart and cleaned them successfully I'm much more versed in the ones off my motorcycles and mowers where there's a bowl and float mechanism. How is the carb pulling the fuel, is it like a pump built into the carb? Also does it make much sense to buy a carb kit, it looks like whole carbs go for around $25 or so and include the fuel bulb etc.

 

[Wood Doctor]

Engine is starved for fuel.
(1) Replace the fuel filter
(2) Open up the low speed setscrew about a half turn (CCW)
(3) Increase the idle speed set screw a half turn (CW).

Try again after doing this and report back. If it fails, carb must be either rebuilt or replaced.

 

[Moto Mike]

Engine is starved for fuel.
(1) Replace the fuel filter
(2) Open up the low speed setscrew about a half turn (CCW)
(3) Increase the idle speed set screw a half turn (CW).

Try again after doing this and report back. If it fails, carb must be either rebuilt or replaced.

I'm guessing that the filter must be the cylinder on the end of the fuel pick-up in the carb. Is there a method for pulling and replacing this that doesn't require major tear down? At a glance it looked like I would need to disassemble the tank from the body to get to this piece unless I had some special tool for reaching it through the hole for filling the tank, which I could see getting it apart, but not back together. The tank appears to be a split casing unit that is partially tank and partially chassis of the saw with seals or something and it looked like a pretty major tear down to get to that level although I never actually saw the bolts that must hold that together when I pulled the two sides off trying to trace the lines and see where everything was coming and going to look for cracked fuel lines. I did try opening the low speed set screw and that helped with idling off choke some but didn't do anything to solve the issue of it usually wanting to bog down on attempts to rev it up or when it does rev up it suddenly dying off like it ran out of gas.

 

[Ketchup]

It may be starved for fuel or it may be leaking air. Try the carb adjustments mentioned above. If that doesn’t help, definitely stop running it until you find your problem.

Before you get too far in, take the muffler off and look at the piston. If the piston has significant grey streaking, you’re in for a full tear down. If it looks shiny and you can see machine marks, that’s good.

If your primer bulb is repeatedly showing air, then you probably have a leak in you fuel circuit. The fuel lines are under a white plastic panel on the top of the saw beneath the top handle. It just pops off.

The fuel filter is accessed by opening the tank, hooking the fuel line and pulling it up to the cap hole. Fight the filter out of the tank and don’t let the line snap back down into the tank if you take the filter off. A $5 pair or hemastats will really help.

Remove the carb entirely and rebuild it or replace it with new. Buy OEM. Many of the Chinese ones don’t work at all.

While the carb is off, test your fuel lines for leaks. You will need some sort of light pressure pump. I use a Mightyvac, but there are many others.

It is also possible that you have an air leak in the engine itself. If you don’t have luck with a new carb and fuel line examination, check to make sure your intake boot isn’t torn. If it’s good, then you need to pressure test. At that point you’re pretty deep in and likely will end up tearing the whole saw down.

Don’t be intimidated to tear the whole saw apart. They’re built for that. It doesn’t even take that long.

I recommend you do some Google searches and watch some YouTube videos. You’ll get it sorted pretty quick.

 

[Wood Doctor]

Impurities which enter the fuel tank are trapped by the fuel filter. Its fine pores can become clogged with dirt particles so that fuel can no longer be delivered in the quantity that the engine needs. You can remove the fuel filter (pickup body) from the tank with a hook that you can make in your shop with stiff wire that has a hook on one end and room on the other end to hold it. Pull the pickup body out of the tank and be careful not to overextend the fuel hose. Then replace it by disconnecting it from the fuel hose and adding a new one. You do not need to disassemble the tank.

Stihl recommends that the pick-up body be replaced first if the engine becomes starved for fuel. That's whyI listed that as step (1) above. There is no setscrew setting on the carb that will solve anything if the fuel filter is clogged.

 

[Moto Mike]

Thanks for all the feedback guys, The next time I get some shop time between diaper changes and bills I'll take a closer look at pulling that filter and seeing if any of my local guys has just that handy. Then I'll work my way toward the more disastrous end. I doubt i'm looking at a full tear down because the saw pulls good when it's pulling, it just chokes out too much to be useful.

 

[casey.jk]

Maybe it's the tank vent. After it kills open gas cap and if it starts and runs for a little that's where I would start.

 

[Van462]

Another easy check is to remove the clutch cover and remove the spark arrestor screen. It they get gunked up it they can cause similar issues. If it runs fne without then take the screen and clean it by heating it with a propane torch until it glows.

 

[tomdcoker]

If you replace the carb. make sure you take pictures or get an IPL. I have been into a 192T a couple times and they are doable if you have any mechanic skills and any patience. Tom

 

[Captain Bruce]

I'm guessing that the filter must be the cylinder on the end of the fuel pick-up in the carb. Is there a method for pulling and replacing this that doesn't require major tear down? At a glance it looked like I would need to disassemble the tank from the body to get to this piece unless I had some special tool for reaching it through the hole for filling the tank, which I could see getting it apart, but not back together. The tank appears to be a split casing unit that is partially tank and partially chassis of the saw with seals or something and it looked like a pretty major tear down to get to that level although I never actually saw the bolts that must hold that together when I pulled the two sides off trying to trace the lines and see where everything was coming and going to look for cracked fuel lines. I did try opening the low speed set screw and that helped with idling off choke some but didn't do anything to solve the issue of it usually wanting to bog down on attempts to rev it up or when it does rev up it suddenly dying off like it ran out of gas.

I would strongly be ready to replace parts, and get them on hand. IE: when you pull the fuel filter up, and out of the tank, remove it and install a new one. $5. I have this saw in front of me, on my bench, where it has been for weeks. Same issue as yours. Print a parts list and refer to these dedicated charts for every step of disassembly/re-assembly. They are FREE. https://www.smaf-touseau.com/doc/38 They are invaluable.

I'm a small engine mechanic, and not shy about new machines. The 192 comes apart like its co-operating with you. The saw had a cracked intake boot. $5 When putting it back together, refer to some photos re: the fuel, prime, and impulse lines. The top handle comes apart, and back together the easiest. Feel Free to pick my brain. Good Luck.