Stihl 028av keeps flooding

[Bakatare]

I have an 028, with a new carb kit, (and I DID pressure test the needle), good spark, good compression, and new plug.
As soon as I crank on it a couple times, it seems it is just sucking fuel into the cylinder and soaking the plug.
This is the first saw I have dealt with that has the impulse line, so I'm not sure how it's supposed to act.
I discovered that someone previous to me had inserted a set screw in the vent line from the tank, so I replaced the line after determining that this was what was causing a pressure build up in the tank causing a hissing that I could hear through the plug hole after cranking it.
Still, it seems to be sucking fuel into the cylinder.
When I checked the impulse line, it pulses, but after a couple cycles of the piston ends up with positive pressure, but the thing that has me buffaloed, is that vacuum applied to the fitting on the carb for the impulse line sucks fuel directly into it.
Do I have a bad carb or is there an issue with the impulse line?

 

[mike515]

Did they reinstall the carb correctly or is there a chance that the intake boot isn't sealed properly?

 

[Bakatare]

Did they reinstall the carb correctly or is there a chance that the intake boot isn't sealed properly?

I've had the carb off 3 times, checking and rechecking, the first time just to check if they had done the rebuild right, and switched the diaphragm and gasket, as they were reversed (gasket closest to the carb, then the diap.), and the other side was correct, and making contact with the lever for the needle, but didn't check the intake boot.
The carb is on properly, but I don't see how that could cause flooding, but I'll check that in the morning just in case.
I was thinking it was somehow related to the carb and the fuel being pulled into the impulse line, but obviously, IDK.
Thanks for the idea.

 

[mike515]

I'm really not a carb expert but I've had a few saws over the years that had fuel, air and spark but wouldn't start...it was the boot. That was just my first thought. It doesn't take a lot for them to cause problems. They need to be sealed just right.

 

[Bakatare]

I'm really not a carb expert but I've had a few saws over the years that had fuel, air and spark but wouldn't start...it was the boot. That was just my first thought. It doesn't take a lot for them to cause problems. They need to be sealed just right.

OK, thanks. I'll keep that in mind.

 

[HD2010]

When you say pressure checked needle, how did you do that? My first thought is choke lever is not working. There is a lever on bottom right corner of air filter that should close off choke in filter when switched is put to choke. The impulse hose delivers pressure and vac from crankcase to fuel pump (diaphragm ). The set screw in vent line is suppose to be there. It's called a vent insert. Not sure I follow on the vac applied to impulse fitting on carb.
The pump diaphragm side should be carb, diaphragm, gasket and then cover. The metering side of carb should be carb, gasket, metering diaphragm and then cover.

Walbro and Tillotson both have great websites to get more info. Part numbers and installation instructions.

What started this problem? Who rebuilt carb.

If this does not help out you might get better and quicker answers on the chainsaw forum section. Lots of guys smarter than me there.

 

[Bakatare]

When you say pressure checked needle, how did you do that? My first thought is choke lever is not working. There is a lever on bottom right corner of air filter that should close off choke in filter when switched is put to choke. The impulse hose delivers pressure and vac from crankcase to fuel pump (diaphragm ). The set screw in vent line is suppose to be there. It's called a vent insert. Not sure I follow on the vac applied to impulse fitting on carb.
The pump diaphragm side should be carb, diaphragm, gasket and then cover. The metering side of carb should be carb, gasket, metering diaphragm and then cover.

Walbro and Tillotson both have great websites to get more info. Part numbers and installation instructions.

What started this problem? Who rebuilt carb.

If this does not help out you might get better and quicker answers on the chainsaw forum section. Lots of guys smarter than me there.

I have the tool, like a vacuum gauge but applies pressure to make sure your needle is seating.
Funny you mention the choke though, because that's the first thing I noticed, was there is no actual choke flap on this Walbro, just the throttle blade, but nothing is missing, meaning no empty holes that I saw like for another shaft or anything.
As far as 'vac. applied to carb', I meant by hooking up a low pressure fuel press/ vac gauge to the impulse line, it pulses back and forth as one might expect as I pull the pullcord, but after a couple pulls and stopping, it actually holds just a slight positive pressure.
The whole time I have been messing with this, I've had the filter off, but to your last couple questions, it's a friend's saw.
He did the carb himself, messed with it for a while then got fed up with it. I'm not sure, so going to ask him WHY he did the carb-was it not running before, or was it running 'poorly', you know.
When he first brought it to me, I richened up both the idle screws and the high RPM screw out to a total of 2 turns from bottomed out, which is where I usually start when I don't know what has been done.
It sputtered on the second or third pull set to choke, so I kicked it down one step, gave another pull and it fired, but ran like it was lean.
I did manage to get it cranked again, and tried both richer and leaner on the high side, but still could not get full throttle out of it without feathering the throttle, and it still would not idle.
I checked the plug, saw it was wet wet, obvious excessive fuel, so I got a new plug, leaned both screws back to 3/4 turn (which is what they were when I got it in hand), and haven't been able to do anything since to get it to do more than give a little sputter on the first pull (using a clean plug every try of course), then I'll pull the plug and it's soaked again.
It has been a while, but I've done these carbs before for a couple friends, without the equipment here and never had a problem when they took the carb home and put it back on, but I don't recall ever having to plug the fitting on the carb for the impulse line when I pressure tested the needle.
This one here, I can blow straight through the fuel inlet out the impulse fitting, or suck on the impulse fitting and get air from the fuel inlet, but vice-versa.
Hey, and thanks for the tips on the websites too.

 

[066blaster]

I had a similar problem with my 066. It would flood to the point of gas running out of the muffler after 2 pulls. Everyone on the chainsaw forum said it was the height of the metering lever. ( it needed to be lowered)

It was weird because if I laid the saw on its side and loosened the gas cap it would not do it the next time I started it, and it did run perfect. Anyway I had my brother in law rebuild the carb , new impulse line and air filter. And it starts and runs perfect. Not sure if he adjusted the metering valve lever or not.

Another problem I had was when I ran 110 octane race gas in it.. it would not run right at all .

 

[Bakatare]

I had a similar problem with my 066. It would flood to the point of gas running out of the muffler after 2 pulls. Everyone on the chainsaw forum said it was the height of the metering lever. ( it needed to be lowered)

It was weird because if I laid the saw on its side and loosened the gas cap it would not do it the next time I started it, and it did run perfect. Anyway I had my brother in law rebuild the carb , new impulse line and air filter. And it starts and runs perfect. Not sure if he adjusted the metering valve lever or not.

Another problem I had was when I ran 110 octane race gas in it.. it would not run right at all .

Thanks man.
After checking out the Walbro site, recommended by HD, they mentioned that, and showed it in the pic...........
And needless to say, when I asked if gaskets, diaphragm and everything had been matched up, they had not, so that was going to be my first thing to try tomorrow is look in my stash and see if I had a shorter/ lower lever.
Funny you mention the octane, because since new, I have run only Stihl bar oil and 89 with Stihl 2 cycle plus a splash of Redline 10/30.
I had just gone down and looked, tore the top cover back off, and the carb, looked down the boot with a flashlight, and could not see any light on the outside, but that is still in my craw as well.

 

[HD2010]

The choke flap is inside the air filter. The air filter will need to be on when starting cold. You could try to start with thumb over carb inlet. Once warmed up you can start without filter. When you pressure check carb it should hold pressure. I check at 5-7 psi. You should not get air to the impulse hose. I hope I read that correctly. The needle lever can be adjusted, no need for a a shorter or different one.

 

[Bakatare]

Thanks man.
After checking out the Walbro site, recommended by HD, they mentioned that, and showed it in the pic...........
And needless to say, when I asked if gaskets, diaphragm and everything had been matched up, they had not, so that was going to be my first thing to try tomorrow is look in my stash and see if I had a shorter/ lower lever.
Funny you mention the octane, because since new, I have run only Stihl bar oil and 89 with Stihl 2 cycle plus a splash of Redline 10/30.

The choke flap is inside the air filter. The air filter will need to be on when starting cold. You could try to start with thumb over carb inlet. Once warmed up you can start without filter. When you pressure check carb it should hold pressure. I check at 5-7 psi. You should not get air to the impulse hose. I hope I read that correctly. The needle lever can be adjusted, no need for a a shorter or different one.

OK, thanks.
Yes, you did read correctly.
I will look at the filter for the choke, and I'll pull off the cover on the needle side and pressure test to make sure the lever is not being depressed, and see if that makes any difference with the flow going straight through the impulse fitting.

 

[Bakatare]

Well, no luck so far.
I re checked the carb, and seems fine, except I still cannot figure out why air or fuel is bypassing and going through to the impulse fitting.
I put it back on, installed the air filter (saw the choke flap, and it works), and after 4 pulls, had enough fuel to be dripping out the exhaust and off the plug when I pulled it out.

 

[HD2010]

The lever should be even with the bodd

Well, no luck so far.
I re checked the carb, and seems fine, except I still cannot figure out why air or fuel is bypassing and going through to the impulse fitting.
I put it back on, installed the air filter (saw the choke flap, and it works), and after 4 pulls, had enough fuel to be dripping out the exhaust and off the plug when I pulled it out.

Carb does not hold pressure correct? Something does not right with carb. I wonder if rebuild kit was correct? Can you verify from owner what kit was installed?

 

[Bakatare]

The lever should be even with the bodd


Carb does not hold pressure correct? Something does not right with carb. I wonder if rebuild kit was correct? Can you verify from owner what kit was installed?

Thanks for all the idea man.
I appreciate it.

I DID ask the guy if he had matched up everything when he threw it back together, and of course, the answer was 'no', but I finally found a Youtube vid that showed the guy disassembling one of these, and YES, the diaphragm I have in front of me is one of the extras that are always included in the kits.... NOT the correct one.
I'm checking with him now to see if he has the rest of the unused parts, and if not, I'll just grab a kit tomorrow.
Just my luck this is one I'm out of.

 

[HD2010]

Thanks for all the idea man.
I appreciate it.

I DID ask the guy if he had matched up everything when he threw it back together, and of course, the answer was 'no', but I finally found a Youtube vid that showed the guy disassembling one of these, and YES, the diaphragm I have in front of me is one of the extras that are always included in the kits.... NOT the correct one.
I'm checking with him now to see if he has the rest of the unused parts, and if not, I'll just grab a kit tomorrow.
Just my luck this is one I'm out of.

Your welcome.
Hopefully that is the problem.

 

[Molly12345]

I have an 028, with a new carb kit, (and I DID pressure test the needle), good spark, good compression, and new plug.
As soon as I crank on it a couple times, it seems it is just sucking fuel into the cylinder and soaking the plug.
This is the first saw I have dealt with that has the impulse line, so I'm not sure how it's supposed to act.
I discovered that someone previous to me had inserted a set screw in the vent line from the tank, so I replaced the line after determining that this was what was causing a pressure build up in the tank causing a hissing that I could hear through the plug hole after cranking it.
Still, it seems to be sucking fuel into the cylinder.
When I checked the impulse line, it pulses, but after a couple cycles of the piston ends up with positive pressure, but the thing that has me buffaloed, is that vacuum applied to the fitting on the carb for the impulse line sucks fuel directly into it.
Do I have a bad carb or is there an issue with the impulse line?

Change the air filiter to oem the choke is built into it and the springs sometimes are weak and don’t operate correctly