Need Help on a Stihl 038 AV

[jwillett]

My son's friend ask if I would look at a saw that was given to him and see if I could get it running. He had tried a new plug and that did not help. I put in fresh fuel mix and tried to start it up but with no luck at all, not even a suptter. I started by checking for fire the cheating way by putting about 3 drops of fuel mix into the carb at the butterfly, the saw started right up. So I next check out the fuel line and filter and found this.

So I got a new fuel line and filter and though I was good to go but still nothing, not even a sputter. I pulled the carb and found this:

The small screen was totally stopped up so I cleanned it up with carb cleanner along wiith the rest of the carb, to late today to find a carb kit anywhere. I put it all back together and still nothing at all. I could get it running with some fuel mix in the carb and it would run fine for a few seconds and then die. I did check the tank vent and it is clear. I did a compression test and only have 70 PSI so that's not too good. I guess I need to wait to get a carb kit and go from there or am I waisting my time? Thanks for any input on this saw.

Thanks,
Jim

 

[Stihlmech]

I would pull the carb all apart and let it soak in fuel for awhile, maybe while your waiting that carb kit. Then when your ready to put it together spray every hole with. BRake cleaner. Then assemble. Pull a vacuum on the fuel inlet hose. About 10 psi. If it holds it should be good. Put it together and adjust to factory specs. Then start it up.

 

[Mad Professor]

70 psi is mighty low


i'd pull muff and have a look at the P/C

 

[jwillett]

I pulled the muffler today at break and the piston and cylinder look in good shape. Trying to get to the impulse line I pulled the clutch cover and found this.

Looks like the oil pump drive gear melted. Guess I need to get a book to learn the correct way to take this thing appart as I pulled the driven gear off the shaft of the pump.
Guess I will need a new pump now. The saw has a good pop to it when pulled over, feels better than 70 PSI to me so I stopped by my friends shop and used his compression tester just to check to see if mine was off, it was not as his read 70 PSI too. I know if I can get fuel to it it will run but that is the problem so far, now how well it will run is another issue. LOL

I just can't understand why I can't get this thing to pick up fuel from the tank, I guess it just a 4 stroke guy trying to work on a two stroke thing. LOL

Thanks,
Jim

 

[Stihlofadeal64]

70 psi is mighty low


i'd pull muff and have a look at the P/C

Check the piston, if it is not scored there is a problem with your compression tester. The saw has been sitting a while I'd say. Looks like the carb was full of cr*p. The line was weenee soft and the filter has seen better days. (If the piston is not scored I'd be pleasantly surprised...and so will you!)
Happy fixing! :msp_biggrin:

 

[lone wolf]

Did you pull it till it stopped rising 10-12 pulls?

 

[jwillett]

Pulled muffler and the piston and cylinder look good. Pulled the engine over about 20 times with carb wide open during the compression test. Went to friends shop and tried his compression gage and got the same reading. The saw has a good pop to it when it is turned over, can't bealive it only has 70 PSI compression. Trying to get to the impulse tube to check it and found the oil pump drive gear melted. Not sure what this saw has been through in it's lifetime. What gets me is if I put just a small amount of fuel mix in the carb it will fire up first pull. Just got to find why I can't get fuel to the carb, when I do we will see how it runs then. LOL

Thanks,
Jim

 

[lone wolf]

Worn out it should have 150 plus!

 

[Stihlmech]

Do what I told you on that carb. Telling you I do it everyday.

 

[Stihlmech]

If it fails the goto baileys and get a bing reproduction They are cheap.

 

[jwillett]

Do what I told you on that carb. Telling you I do it everyday.

Waiting on the kit, will start soaking the carb tonight.

 

[Stihlmech]

Just make sure that you spray every hole out with brake cleaner before you put it back together then only put 10psi max on it

 

[jwillett]

Just make sure that you spray every hole out with brake cleaner before you put it back together then only put 10psi max on it

Thanks, will do. I kind of hope to get this thing running and the guy will let me have it for cheap. I passed on a good looking 026 on Craig's list for $100.00 Sat. Hoping to make this saw work instead. I already have a great running 026, just want something bigger.

Thanks,
Jim

 

[jwillett]

It's alive, soaked the carb a while, put it back together and it fired right up. I tuned the carb and got good throttle response and left it fat on the top end for now (no chain). Need to get oil pump gears and see whats up with the low compression, 60 PSI now hot, think rings may be stuck.

Thanks for the help,
Jim

 

[Stihlmech]

You might wanna check that with another tester. Do it while it's hot and with a wide open throttle. Never seen one run under 80 psi.

 

[jwillett]

You might wanna check that with another tester. Do it while it's hot and with a wide open throttle. Never seen one run under 80 psi.

Yep, I have already tried another compression gage from my friend's shop, same reading, all reading taken with throttle wide open. Got the Sea Foam working on the rings now, piston and cylinder looked too good to be this low on compression.

Jim

 

[Stihlmech]

I would just pull the cylinder off and look at it. It's really not that difficult. Top shroud exhaust and 4 bolts and the intake About 30 mins off and on. That is what I would do. That way you know for sure. Try that if the sea foam don't work.

 

[jwillett]

Well I pulled the cylinder and found nothing I could see out of the way. Not sure about the ring end gap, looks a little much to me but I am going through the manual looking now. Cylinder looks great, piston looks good, not sure what to think if this. Any ideay why I only have 70 PSI compression?

The Pictures:

Thanks,
Jim

 

[MillwrightChris]

I don't know why but some compression testers don't work well with small engines. I have one that works fine on cars but every saw I put it on it reads 80psi no matter how many times you pull it.

 

[Stihlmech]

The cylinder looks good to me. I would put on a new set of rings. Looking at the pics I see small areas that looks like a groove. And run a little sea foam through it when you fire it back up. It will clean the top of the piston off for you. And also clean out the rest that you really can't see. That's just my opinion.