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Stihl 390 hard starting?

Started by logman81, March 22, 2013, 07:20:45 AM

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logman81

I have a 390 stihl, starts just fine when could but it is next to impossible to start once it is warm why is this?
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AdkStihl

Many reasons why that could be. Here a few.

Plugged Tank Vent
Low Compression / Scored Cylinder
Bad Ignition Coil
J.Miller Photography

logman81

The saw doesn't have that many hours on it. It starts right up fine when cold and idles and runs good when using it. But when I shut it off after using it and go to re start it it won't start. Could it be a carb adjustment?
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joe_indi

A partially blocked pickup body (fuel filter) could be the culprit.

Joe

JohnG28

You might try opening the L adjustment up a little. My 361 used to be this way before a little tweaking.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

beenthere

QuoteBut when I shut it off after using it and go to re start it it won't start.

Do you attempt the warm re-start it with the choke off and throttle set at idle?

south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

logman81

Yes I tried adjusting the L screw no better.
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logman81

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pineywoods

When you find the problem, please let us know what's causing it. I have an 029 with the exact same symptoms. Hot, cold, warm, choke, no choke, it doesn't matter, at least  7-10 good pulls to get it started. Otherwise runs good, idles good, plenty power. New plug didn't help.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

logman81

Ok will do, never had a problem with a saw I couldn't figure out.
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ladylake

 
Try holding the throttle wide open on hot starts, if that helps the needle valve could be leaking a bit causing it too flood.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

bandmiller2

Some perfectly good saw take many pulls to start I do believe the fuel drains back into the tank.Hot start problems are like a vapor lock gas expands to vapor and pushes gas back to the tank.Have a 041 stihl that will usally start on the first pull,my 365 husky takes many pulls boath are good runners,may just be their personalities. Frank C.
A man armed with common sense is packing a big piece

macpower

Try it with some fresh, non-ethanol fuel mix and see if it acts the same. Rule out the simple things first.
Purveyor of Stihl chain saws.
Thomas 6013 Band Mill, Kubota L3400DT, Fransgard V3004, 2 lazy horses and a red heeler

logman81

Like the vp small engine fuel, I used it a couple times last year on another saw with good results. I may just bring it to the dealer for a tune up.
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gwilson

My 441 Magnum is hard to start when its hot as well. I was told that the new stihls were designed to start in a warm start mode which is the second choke up from the bottom (high idle) setting. A dealer told me that they would not crank in the run position. Just a thought

clww

Every Stihl I've ever had has had a distinct, unique personality all it's own.
Many Stihl Saws-16"-60"
"Go Ask The Other Master Chief"
18-Wheeler Driver

logman81

Yes they do, I bought a new ms650 and it blew up three times in two weeks until they figured out they needed to be detuned to run on the new ethanol gas.
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clww

Thinking more on it, I've had a couple that had multiple personalities.  teeter_totter
Many Stihl Saws-16"-60"
"Go Ask The Other Master Chief"
18-Wheeler Driver

lumberjack48

Its ether flooded or starving for fuel, find out which one it is.

All the Stihl's i had would start with about a 10 inch pull when hot.

I got to thinking, when i had one act up like this, i swapped the plug, it was that simple.
Third generation logger, owner operator, 30 yrs felling experience with pole skidder. I got my neck broke back in 89, left me a quad. The wife kept the job going up to 96.

Ianab

My MS310 can be a bit temperamental when it's just a little warm.

Cold is OK, 3 pulls with the choke and it pops, then 3 on fast idle and it starts.
Hot is fine, 1, 2, or 3 pulls on fast idle and it's going.

It's when it's been sitting for maybe 10 minutes, while you are doing other stuff. Do you warm start it? Or cold start it?  If you use the choke and it didn't need it you end up flooding it, and that's a real pain.

So I usually try a warm start first, if it doesn't fire, ONE pull with the choke, then back to the warm start and it fires up.

But like the guys say, saws do have personalities...  :D

I also agree that a sick spark plug can do weird things. Simple and cheap to replace and see what happens.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

JohnW

I don't know if this is your problem, but I just don't think Stihl did a very good job on the choke control for 390 / 310 / 290 saws.  My 310 is the only example I have so maybe I'm just prejudiced.  I had to have the carborator rebuild recently and I had a good mechanic to do it.  He spent a little time rebending the choke control spring, so I can easily switch it from full choke to half choke.  It used to be a fight that required both hands.  He spent a lot of time adjusting the slow idle and fast idle.  And it runs and starts like it never had, so I blame Stihl for that.

MakitaCS

Quote from: logman81 on March 22, 2013, 08:51:09 AM
The saw doesn't have that many hours on it. It starts right up fine when cold and idles and runs good when using it. But when I shut it off after using it and go to re start it it won't start. Could it be a carb adjustment?


I recently sent a 346xp with finger ports that run through the cylinder to Nathan, aka Metals406 for those of you who know him. I thought maybe something had gone astray on this porting this time around because no matter what, trying to start the saw on a hot start was useless. Choke, part throttle, whatever, it didn't matter. It would usually take 7-8 pulls in the ON position or 3-4 pulls in the part throttle for it to finally turn on. That's useless when you got a job to do. Like many, I thought it needed more fuel off the L circuit. It never solved the issue.

So I start to look things over and at one point thought I had things figured out. The saw leaked whenever I put the saw on its clutch side. Sure enough, the vent tube was not pushed all the way in flush against the vent. I also discovered for those of you who know the 346, that there was no hole in the air filter housing where the vent tube connects to the nipple. I drilled a hole and thought, case solved, as it wasn't breathing properly. Nope. It didn't help at all.

So I finally sent the saw to Nate to try out timber falling and told him about the problem. That's where the magic happened for this saw. He noticed that the idle screw was set far too in. So he sets the L and H needles to zero and the same for the idle screw. He then proceeded to start at 1 1/2 turns out on both the L and the H. He got it to fire and adjusted the idle via the L and not the idle screw. He then set the H. Done. He says of all the saws in his lott, this 346xp starts and idles the best, hot or cold. If I remember correctly, he barely if at all, touched the idle screw.

You probably wacked the tuning way off like I did. It's worth a shot, you never know.
CHEVYTOWN13

logman81

Could be, I think it is a rich condition but not to sure.
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