Stihl 028 runs great, then dies after 15 mins or so, every time...

[Okie294life]

I had one with the exact same issue, or close to it. I finally took it to the shop and got it pressure tested, it was the had gasket sucking air. It was crazy because if you leaned it on one side it would run like crap, as if the crank seals were bad, but I knew they weren’t because I had just replaced them. May want to get it pressure tested or pressure test it yourself. Air leaks can be deceiving and by the time you figure it out you may have smoked a piston.

Have a Stihl 028 that I picked up used. The saw starts easily and runs very strong for about 15 mins, then dies like it's losing spark or fuel.

Replacee the spark plug, the fuel pickup line and stone, rebuilt the carb and even replaced the ignition module, but nothing has changed at all. Still runs great for 15 minutes, then dies. Let it cool completely, and it will do it all over again.

I'm almost at my wit's end with this one, and I need firewood for this winter!

Any thoughts or suggestions are greatly appreciated.

Thanks!

-Tony[/QUOTE

My customer this morning delayed until 1:00, so I went out to test the 028 some more.
View attachment 669095

Put saw on the gap tester and it would jump 3/8", but not 7/16" or 1/2".
170 PSI on the comp tester
I did NOT pull the grubs or vent line.

It started right up 2nd pull, and ran for a good half-hour this time, running smooth as silk through a large white oak. This really is one of my favorite saws. Then it started losing power, and within a minute it was dead and wouldn't restart.

Thinking about the fuel issue, I loosened the gas cap and tried to restart. Nothing. So I took over to the shop to see how things compared...

Temp on the head was 193 degrees, 187 on the spark plug.
Neons showed... Good spark???
Gap test showed it jumped 3/8" gap. HUH!?!?
Compression was 160 psi
No unusual tension when I pulled the cord.

With this information, I re-filled the gas and oil, (in case it's a cracked pickup line) hit the choke, and she started up for a second. HUH! I ran over to the wood pile, restarted and tried cutting. She ran, but felt a little weak, so I cracked the cap open and cut sideways, and she immediately shut down and wouldn't restart. Closed the cap and eventually got her restarted AFTER hitting the choke again. She kind of surged between more power, then less, then shut off again.

This time I ran over to do a temp and comp check. Temps this time were around 240 degrees on the head and plug, but apparently, it cools off pretty fast, because it dropped very quickly to 190 then 140. Compression still at 160 psi.
View attachment 669094

I seem to have good spark at all times, and the compression seems very good and consistent. It appears that this is a fuel issue, not a spark issue, which is a little surprising to me, since I have tried all of this before, and never got this far.

I have to run to my job now, but when I get back, I'm pulling the vent grubs and will re-test.

Here are some pics this time. The saw is in average, used condition, as you can see. Not beat up, but not super clean either. One shows the plate and what I think is the serial number. Is the number all the way to the right the serial number? Would 0000 967... mean it was made in July 1996?View attachment 669093
Sorry for all the noob Stihl questions. I've run a Homelite Timberman 45 for the last 20 years, (has been a great saw!) and this is my first Stihl, although I have an 021 for limbs, and it runs flawlessly since I replaced the fuel pickup hose and stone.

Very appreciative of the encouragement and knowledge you guys have!

-Tony

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[Okie]

You better keep a heads up on the 028 carb H jet adjustment and make sure it's not set on the lean side or you WILL HAVE a melt down eventually.

I would think about trying to repair and re-install the OEM carb instead of leaving the China Clone carb on the Stihl as a permanent fix.