What do you do when a warm saw will not restart

[golfandwoodnut]

I have had this problem a few times where my MS 390 starts normally, and runs fine. But then I stop it, for whatever reason, and then I cannot get it restarted. Choked, 1/2 choked, not choked. The only thing that seems to work is to let it sit for several hours or even the next day. I tried it today (a day later) and it fired right up. I am assuming the plug is getting wet and I need to let it dry out. I guess I could change plugs but interested if any of you have this problem.

Fortunately I have backups so I was able to keep going with one of them. I am cutting up the monster ash on my property that holds 7 and 1/2 cords and just doing a tank or two of gas each evening while it is cool.

 

[NH_Wood]

Have tried opening the gas cap when the saw won't restart? Sounds like a vapor lock perhaps. Check tank vent. Not an uncommon problem on saw. Cheers!

 

[bogydave]

Threaten to trade it in for a new MS362

I have an old Husqy 61, starts normal when cold, after it gets hot,
I give full throttle & pull to get it started.

 

[MrWhoopee]

Hold throttle wide open, if you can't set it there, then pull it.

Works on my Redmax

 

[Hills Hoard]

Have tried opening the gas cap when the saw won't restart? Sounds like a vapor lock perhaps. Check tank vent. Not an uncommon problem on saw. Cheers!

my thoughts too.

 

[MasterMech]

I'm thinking the saw would stall at or lose power if the tank vent was blocked. If holding the throttle wide open starts the saw, then I also would be curious as to where all that extra fuel is coming from. The saw idles well?

 

[Thistle]

Have tried opening the gas cap when the saw won't restart? Sounds like a vapor lock perhaps. Check tank vent. Not an uncommon problem on saw. Cheers!

That happens to me maybe once or twice a year,on a real hot day after heavy use.I cracked that gas cap open just enough to hear a "hiss",then closed it & pulled the rope again.

Problem solved.

 

[Fifelaker]

Could be either fuel or spark. As soon as it wont start pull the plug if it is wet fuel if it is dry check for spark.

 

[MrWhoopee]

In the online manual
http://www.stihlusa.com/WebContent/CMSFileLibrary/instructionmanuals/MS290_310_390_Manual.pdf

On page 37, we find a section entitled "If the engine doesn't start" with a procedure for correcting a flooded cylinder.
Don't know if it applies, but since they actually documented the condition.....

 

[MasterMech]

Could be either fuel or spark. As soon as it wont start pull the plug if it is wet fuel if it is dry check for spark.

Right train of thought, wrong direction.

And this clearing a flooded engine thing is something I've got to get on video for you guys. Workload has eased up a bit, wife is working tomorrow, supposed to be a beautiful day, hmmmmmm.

 

[TreePointer]

My MS361 would sometimes have hard re-starts when engine is hot in warm weather. Opening the fuel cap for a second when finished prevents this.

I have a Makita 7901 that had the difficult restart problem all the time. I opened the carb's Low jet 1/8-1/4 turn and this problem stopped.

 

[golfandwoodnut]

wow, as usual, thanks for all the fast responses. I will try the gas cap trick next time and see if that works. It does get frustrating when you pull and pull and nothing.

 

[n6crv]

It means it is time to call it a day.

 

[smokinj]

This maybe stupid question but are you choking that hot saw? (And my real answer would be: its time to head for the House)

 

[hiker88]

Have tried opening the gas cap when the saw won't restart? Sounds like a vapor lock perhaps. Check tank vent. Not an uncommon problem on saw. Cheers!

This. I was cutting Sunday at it was really hot. I twisted the cap, and there was so much suction I had to really tug the cap out and it came with a long hiss. Put it in and I was able to restart.

 

[golfandwoodnut]

I was doing some research and an "awarded best answer" in another thread is that the coil may be going bad. A coil will work better when a saw is cold and is able to work while the saw is running but may not be able to work to restart a warm saw. I remember having a problem with the saw when I first bought it where it would not start and they told me the coil was not making good contact. I wonder now if it was always a shaky coil.

 

[charly]

I do the wide open throttle and pull her over.. works anytime I need it.. Just have to be careful.. MS 360

 

[TreePointer]

The first two easy things I try when a hot saw will not restart are as follows:

1. As mentioned above, relieve possible low pressure condition in tank.

2. LOW setting on carb also may be too lean. Saw may not be getting enough fuel for restart. Try richening LOW setting by 1/4 turn or more.

 

[Jack Fate]

I was doing some research and an "awarded best answer" in another thread is that the coil may be going bad. A coil will work better when a saw is cold and is able to work while the saw is running but may not be able to work to restart a warm saw. I remember having a problem with the saw when I first bought it where it would not start and they told me the coil was not making good contact. I wonder now if it was always a shaky coil.

had a simplicity gt do that for years till I found that to be true

 

[Sprinter]

Right train of thought, wrong direction.

And this clearing a flooded engine thing is something I've got to get on video for you guys. Workload has eased up a bit, wife is working tomorrow, supposed to be a beautiful day, hmmmmmm.

Please do. It's a frustrating problem when it happens.

 

[TreePointer]

Think about it--flooded engine means there is too much fuel in engine to have proper air-fuel mixture for ignition by spark. If you have too much fuel, you have two options: 1.) get rid of some fuel, or 2.) add more air to get a more favorable fuel-air ratio.

In 2-cycle engines, the easiest thing is to add more air to the fuel-air mixture entering the cylinder. How? Don't choke it (this restricts air). Don't press on throttle (this doesn't improve the ratio much). Just put it in the RUN setting and pull on the cord a bunch of times (5, 7, 10, whatever) until it fires. Each successive pull also purges the relatively high concentration of fuel present in the initial flood condition.

It works for me, and there is no removing of the spark plug or letting it rest for an hour or half the day. On many saws, I've actually had better results clearing a flood in the RUN position than the Fast Idle or Partial Throttle position.

 

[MasterMech]

Don't press on throttle (this doesn't improve the ratio much).

On many saws, I've actually had better results clearing a flood in the RUN position than the Fast Idle or Partial Throttle position.

Funny cause that's exactly how you clear a flooded engine. Open the throttle and choke to wide open, and crank until it fires. Cars/and trucks with fuel injection (how you flood a FI engine, I'm not exactly sure, ) usually have a routine programmed in that if the accelerator is held to the floor while cranking, it will disable the fuel injectors allowing the operator to clear a flooded engine.

 

[TreePointer]

Yeah, I know that Stihl and others recommend Fast Idle and similar for starting a flooded engine, but that never seemed to work as well as the RUN position for my 2-strokes. Maybe all those frustrating attempts on fast idle did substantial work to clear the flood before switching to RUN and pulling multiple times. RUN position also made pulling easier than with full throttle.

 

[golfandwoodnut]

Another good/bad thing is the compression relief button. When it won't start and you have the button pushed in it almost seems like the saw is less likely to start and it is almost too easy to pull. Without any compression is just seems like I pull and pull and there is no way that I know of undo the compression button.