Stihl MS500i Hot Start Problem

[zslnk]

Hello,
Well I ran out and bought a 500i and I've only put about 3 tanks of fuel through it. I was really impressed until today.

Prior to today, I had only used the saw in cold weather and it was fantastic, I could take it from the warm shop outdoors (-10c) and it would start up and wouldn't miss a beat. Today, in warmer weather, the saw won't re-start when warm. It will start and die or start and if some throttle input is given, it bogs and dies. It would do this for about 30mins after use and now it's running normally. Before I take it to the dealer I'd like to know if anyone else has had these issues?
Thanks

 

[Wood Doctor]

The engine might be having some trouble with the recent higher temperature and humidity. My MS441c was having a similar issue, but not quite that extensive. It got used to it after awhile and seems OK now. It could be a simple adjustment needed. The dealer's mechanic should know.

 

[user 122190]

In addition to not needing a 500i, nor having the money to buy a 500i, it is to new a saw to spend that kind of money. My 461 is going like new after 5 years, and I expect to get another great 5+ years out of it. My ms290 which I use more then anything is now on its 10th year and it too is also running and starting great. Compression test last year tells me that it is very healthy also. I did a carb rebuild to address some rare bogging issues -- 20 minutes of work, $6+ in cost and it is perfect.

500i? Why?

 

[lone wolf]

Are you using pump gas?

 

[farmer steve]

How is the winter/summer shutter set? If it has one. All my Stihls do.

 

[PV Hiker]

Are you using pump gas?

That is winter grade?

Also did you shut it down right after working it hard and it was hot. Heat soaked stopped fuel flow for restart. Let mtronics cool off some before turning off allows computer and sensors to function properly.

 

[zslnk]

I’m using 91 octane pump gas mixed today. The saw doesn’t appear to have a winter shutter.

If I run the saw, shut it off and immediately restart it’s ok. If I run it then wait 5-20min it’s cranky. I’ve also tried venting the gas tank first and it makes no difference.

 

[PV Hiker]

I’m using 91 octane pump gas mixed today. The saw doesn’t appear to have a winter shutter.

If I run the saw, shut it off and immediately restart it’s ok. If I run it then wait 5-20min it’s cranky. I’ve also tried venting the gas tank first and it makes no difference.

So how long did it run after working it before shutting it down? There is a period that you could have slight heating of the fuel system causing a no start or running ruff is a symptom of vapor lock and evaporation of fuel. Starting immediately there is still fuel that has not cooked out by heat soak. Waiting longer after cooling down to restart might not see this condition.

Give it a try running it 30 seconds to a minute for the air to flow over the cylinder and cool fuel to pass inside to cool from within. Mtroncis are more sensitive, it only cost you your time to try.

 

[SteveSr]

I’m using 91 octane pump gas mixed today. The saw doesn’t appear to have a winter shutter.

If I run the saw, shut it off and immediately restart it’s ok. If I run it then wait 5-20min it’s cranky. I’ve also tried venting the gas tank first and it makes no difference.

Vapor lock with winter spec fuel... Runs fine after cool down is the give-away. As others say let it idle a minute before shutting it off to get rid of some of the heat buildup.

 

[Clyde85]

I had the same problem today with my Husqvarna 61, Sachs Dolmar 133 , and sthil ms260.

 

[PV Hiker]

Spring and fall you'll see this more often with the transition of fuel at the pumps.

Filled up the 4 Runner the other day and picked up some miles per gallon. So long winter grade... depending on your source you could have winter grade being sold.

 

[zslnk]

Vapor lock
I opened the fuel tank cap when hot and pressurized air came flowing from the fuel filter for many seconds.

I had tried priming it but not the 8 times as shown in the video. The primer never really feels solid like on traditional 2 stoke yard equipment, it's mushy.

Vapor lock with winter spec fuel... Runs fine after cool down is the give-away. As others say let it idle a minute before shutting it off to get rid of some of the heat buildupI believe this is correct. I found this video that explains it.

 

[TNshag]

Sorry to hear about your issues....but I’m glad you posted this. I’ve been curious if these saws had these type problems. Sounds exactly like my Husqvarna 562xp does after shutting it off and trying to start it back in about 10 mins. Worlds biggest PITA!

I’ve been seriously considering...even jonesing for, lol...a 500i. But I absolutely will NOT have another saw that acts like a Husqvarna 562. Time is money. Once they start first thing in the morning, I should NOT have to crank my damn arm off to get them going again after 15 mins of downtime.

I guess I’ll be sticking with my old 460’s and 660. Choke em to get em going first thing, after that, they’ll start on the first pull. Waiting 2 minutes to idle down and cool off a chainsaw is ridiculous. Choking, holding the throttle, pumping the purge after a 10 minute break, is even worse.

Edit to say: I would love for these genius engineers to come to work with me just one day. I’ll carry the saw and do all the cutting. But they NEED to follow a man to the bottom of the holler, to just need to top that ONE tree that’s there. I just want them to START the saw after a few mins downtime and walk with me step for step. I guarantee THAT would go a long ways towards fixing nonstart issues. If it requires a 2 minute cool down, I’d gladly let them carry the idling saw back up the hill that’s so steep you have to grab ahold of something to PULL yourself back up, until the proper cool off period is reached for an easy restart.

 

[lone wolf]

Same problem every spring here, its winter gas, I keep some Avgas around for these instances there have been days nothing on the truck would run right. ! Get some different gas without ethanol or keep the can and the saw out of sun.

 

[lone wolf]

https://www.gasbuddy.com/go/summer-blend-and-winter-blend-gasoline

 

[Westboastfaller]

Spring and fall you'll see this more often with the transition of fuel at the pumps.

Filled up the 4 Runner the other day and picked up some miles per gallon. So long winter grade... depending on your source you could have winter grade being sold.

That would be pretty early. They usually swap overs in the refineries about now and don't have to have everything out of their holding facilities until May1st and in the pumps before June1st.
It's possible because of this unpredictable pandemic as last year they had to get an extension to may 20 to sell off there storage due to lockdown.
When it does come there is still a 'shoulder season' where it is still a high vapour preasure for the first month. They are likely allowed to marry a percentage up.
They should have it on the paperwork if you talk to some managers around. The price would have went up too.

You can test it easy, yourself

 

[zslnk]

Thanks for all the input. My experience with the saw in the winter was fantastic, one pull and it idled like it should with no priming. I hope that once I get through this fuel the joy returns. I really like the saw as it is light, no tuning is required and has lots of power. I appreciate the responses.

 

[mr.stihl.in.idaho]

Im a mechanic at the local dealership here in the sticks. i have had the pleasure of selling several of these amazing units within the past couple months. i have had rave reviews about the performance thus far up until today. had a customer come in who is a local and uses the saws he purchases to earn a living. he has only run about 3/4 of a tank of fuel through it before the hotstart issue arose for him. As we live about an hour and a half from Boise, I too am inclined to say everyone is correct in saying that the issue is more than likely an issue with the fuel mixture. As this was one of the topics addressed in the Mechanics class i attended just this past tuesday, the fix is pretty simple,\.
Drain the existing fuel from your tank. Start the saw and let it run until all the fuel has been run out of the fuel lines. my number one preference in fuel would be motomix. if you choose not to use moto, use av gas if you have a local station that has fuel that rich. if not than only premium branded ethanol free high octane (premium) fuel and stihl ultra two cycle oil. these engines are designed to take ethanol up to 10 % and no more and alot of the winter fuel is either that or e85. run the saw and let it warm up to operating temp. this will give the onboard computed to diagnose and rediagnose every 15 sec and make adjustments accordingly until it is at its optimum performance. if that doesnt fix your issue than you need to take it to the dealer so they can hook it up to a MDG 1 diagnostic scan tool. this will talk to the saw and find any issue within and remedy the issue or at least tell the mechanic where to look first than provide a pathway from there with a checkbox type option system.
hope this helps as this is the advise i gave the gent who came in to see me.

 

[L34]

I didn't think high octane fuels were any good for saws.Slow burn rate?
Please school me on this.
Chris.

 

[Stihl99]

I didn't think high octane fuels were any good for saws.Slow burn rate?
Please school me on this.
Chris.

Actually the higher the octane the better controlled detonation and explosion happens in the cylinder, that is what all the mechanics have told me.