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2 stroke carb question
#1
A
arch252
A
arch252
Let me start by saying that 2 stroke carbs are my nemesis, I hate working on them. When I'm asked to look at one for a friend I usually end up recommending replacement right off the bat.
I have an Echo PB-2100 leaf blower that I've had for a LONG time, she's been good to me.
It was running rough so I took the carb apart, completely apart and went through it about three times. I replaced the diaphragm. It starts right up now and runs strong....as long as I'm pointing it at the sky! When I lower it the engine will bog down and choke out. If I point it up it runs strong again. Can anyone tell me what I did wrong?
The fuel lines are in very good condition, replaced not long ago. It has a new fuel filter and spark plug. I've blown air into the lines to see if the lines were cracked or had a pin hole but found no leaks.
I have an Echo PB-2100 leaf blower that I've had for a LONG time, she's been good to me.
It was running rough so I took the carb apart, completely apart and went through it about three times. I replaced the diaphragm. It starts right up now and runs strong....as long as I'm pointing it at the sky! When I lower it the engine will bog down and choke out. If I point it up it runs strong again. Can anyone tell me what I did wrong?
The fuel lines are in very good condition, replaced not long ago. It has a new fuel filter and spark plug. I've blown air into the lines to see if the lines were cracked or had a pin hole but found no leaks.
#2
L
logan01
L
logan01
Are you sure the fuel supply tube with the filter is staying submerged in the tank as you shift the blower about? Or venting perhaps. With enough fuel to run but not spill out, try loosening the fuel cap as you begin to lower the blower and see if it'll stay running.
#4
L
Lawnranger
L
Lawnranger
Another possibility is that you have the fuel lines reversed. If the lines were in fact reversed it would make it so the fuel level would cover the shorter return line (which is connected to inlet) when pointed up and provide fuel to the carburetor but not when pointed down. Double check your fuel line connections. If the carburetor has a barbed fitting it should be connected to the fuel supply line.
#6
M
Mikel1
I'm with you on that, rebuilding them is hit or miss.
M
Mikel1
Let me start by saying that 2 stroke carbs are my nemesis, I hate working on them. When I'm asked to look at one for a friend I usually end up recommending replacement right off the bat.
I'm with you on that, rebuilding them is hit or miss.
#7
A
arch252
A
arch252
Logan, I checked the position of the fuel filter and it moves about freely in the tank. I checked to see if the lines were reversed but they were not, they were correct. Any other ideas?
#8
B
bertsmobile1
B
bertsmobile1
Dealing with these on a daily basis I have a few diagnostic tools that you may not.
however with a diaphram carb that is sensative to engine orientation it can only be a few things.
1) cracked , stiff or incorrectly fitted diaphram
2) inlet pipe & return pipe connected back to front
3) crack in fuel inlet tube / partially blocked fuel filter .
Double check the connections.
The tube nearest the primer bulb is the return and goes to the tube that ends just inside the fuel tank, not the supply tube with the fuel filter on.
The primer BLOWS air back into the tank which draws fuel into the other tube.
I have an alternate fuel tank with a known good fuel line that I hook up to the suspect tool.
Problem gone = new fuel line & filter.
The fuel line oft splits near the fuel tank grommet so the carb sucks air when ever that section of tube is above the fuel level.
Similarly with the fuel filter, the bottom gets gummed up so only draws fuel when the upper sections are below the fuel level.
however with a diaphram carb that is sensative to engine orientation it can only be a few things.
1) cracked , stiff or incorrectly fitted diaphram
2) inlet pipe & return pipe connected back to front
3) crack in fuel inlet tube / partially blocked fuel filter .
Double check the connections.
The tube nearest the primer bulb is the return and goes to the tube that ends just inside the fuel tank, not the supply tube with the fuel filter on.
The primer BLOWS air back into the tank which draws fuel into the other tube.
I have an alternate fuel tank with a known good fuel line that I hook up to the suspect tool.
Problem gone = new fuel line & filter.
The fuel line oft splits near the fuel tank grommet so the carb sucks air when ever that section of tube is above the fuel level.
Similarly with the fuel filter, the bottom gets gummed up so only draws fuel when the upper sections are below the fuel level.
#9
A
arch252
A
arch252
Awesome, thanks Bert. I'll double check the diaphragm to make sure it's oriented correctly and check the lines for cracks.
#10
A
arch252
A
arch252
I did an overhaul on the carb tonight. I had a spare matching carb body that I knew was in good shape so I cleaned it again and swapped it out. I put in another new diaphragm and both gaskets. I replaced the fuel lines. I started it up and again it ran strong at first but quickly started to choke out. When I pointed it up in the air it would run good again. So based on that I'm confident this is not a carb issue.
I'm guessing now that perhaps the rubber grommet that the fuel lines pass though is not sealing well. When I tilt the blower up the grommet is submerged in fuel and that's when it runs smooth. When I lower it the grommet is exposed to air inside the tank. I haven's seen any fuel leaking from the grommet but I can't imagine what else it could be. I have replaced that once before. It's a three hose grommet with the third hose going to what I guess is an air check valve. I'm going to replace that and see what happens. It looks in good shape though.
Side note...when I was cleaning out this second carb body I blew out the small screen on the flip side of the needle valve. I was going to replace it with a spare I had but I forgot. If I leave it out am I asking for trouble or would it be alright to run it without it. I've pulled that carb apart about a dozen times now and I'd really like to avoid doing it again if possible. I'm pretty cautious about clean fuel and I've never seen a dirty screen in any of my equipment. I was going to leave it and if the carb fouled up because of it I would just pull it off and clean it then, hopefully a long time from now. Am I crazy for even thinking that?
I'm guessing now that perhaps the rubber grommet that the fuel lines pass though is not sealing well. When I tilt the blower up the grommet is submerged in fuel and that's when it runs smooth. When I lower it the grommet is exposed to air inside the tank. I haven's seen any fuel leaking from the grommet but I can't imagine what else it could be. I have replaced that once before. It's a three hose grommet with the third hose going to what I guess is an air check valve. I'm going to replace that and see what happens. It looks in good shape though.
Side note...when I was cleaning out this second carb body I blew out the small screen on the flip side of the needle valve. I was going to replace it with a spare I had but I forgot. If I leave it out am I asking for trouble or would it be alright to run it without it. I've pulled that carb apart about a dozen times now and I'd really like to avoid doing it again if possible. I'm pretty cautious about clean fuel and I've never seen a dirty screen in any of my equipment. I was going to leave it and if the carb fouled up because of it I would just pull it off and clean it then, hopefully a long time from now. Am I crazy for even thinking that?
#11
B
bertsmobile1
You bet you Charlie you are asking for trouble without that screen.
You have seen how fine those holes are.
As for the problem, good chances you have a split in the hose just where it goes through the grommet.
OR
You have the feed & return tubes transposed.
The return hose goes about 1/4" into the tank past the grommet.
Take the tank cap off and pump the primer.
You should hear the returning fuel "peeing" into the fuel tank.
If not, or you hear it "blowing bubbles" then the intake and return lines are on the wrong carb spigots.
Don't feel silly, we have all done it before.
B
bertsmobile1
I did an overhaul on the carb tonight. I had a spare matching carb body that I knew was in good shape so I cleaned it again and swapped it out. I put in another new diaphragm and both gaskets. I replaced the fuel lines. I started it up and again it ran strong at first but quickly started to choke out. When I pointed it up in the air it would run good again. So based on that I'm confident this is not a carb issue.
I'm guessing now that perhaps the rubber grommet that the fuel lines pass though is not sealing well. When I tilt the blower up the grommet is submerged in fuel and that's when it runs smooth. When I lower it the grommet is exposed to air inside the tank. I haven's seen any fuel leaking from the grommet but I can't imagine what else it could be. I have replaced that once before. It's a three hose grommet with the third hose going to what I guess is an air check valve. I'm going to replace that and see what happens. It looks in good shape though.
Side note...when I was cleaning out this second carb body I blew out the small screen on the flip side of the needle valve. I was going to replace it with a spare I had but I forgot. If I leave it out am I asking for trouble or would it be alright to run it without it. I've pulled that carb apart about a dozen times now and I'd really like to avoid doing it again if possible. I'm pretty cautious about clean fuel and I've never seen a dirty screen in any of my equipment. I was going to leave it and if the carb fouled up because of it I would just pull it off and clean it then, hopefully a long time from now. Am I crazy for even thinking that?
You bet you Charlie you are asking for trouble without that screen.
You have seen how fine those holes are.
As for the problem, good chances you have a split in the hose just where it goes through the grommet.
OR
You have the feed & return tubes transposed.
The return hose goes about 1/4" into the tank past the grommet.
Take the tank cap off and pump the primer.
You should hear the returning fuel "peeing" into the fuel tank.
If not, or you hear it "blowing bubbles" then the intake and return lines are on the wrong carb spigots.
Don't feel silly, we have all done it before.
#12
A
arch252
A
arch252
You're right, guess I'm breaking it down again tomorrow to put that screen in. I have double checked the hoses, the one closest to the primer bulb is venting back into the tank, the other is connected to the fuel filter.
#13
B
bertsmobile1
That sounds right so looks like you have a hole or split in the fuel pick up hose.
They tend to go hard & crack just past where they exit from the tank grommet inside the tank.
Echo make a complete replacement set, both hoses, the filter & grommet which is the easy & safest way to go.
If the fuel line is hard & cracked then the grommet will not be pristine either.
If you are not intending to replace ht grommet then do not remove it as old ones rarely reseal properly.
Use Tygon fuel line, should cost $ 2 to $ 5 for the 6" length you will need.
Just make sure it is the right size.
Supply tube is heavy walled to prevent the tube collapsing onto itself.
Return tube is thin walled.
B
bertsmobile1
You're right, guess I'm breaking it down again tomorrow to put that screen in. I have double checked the hoses, the one closest to the primer bulb is venting back into the tank, the other is connected to the fuel filter.
That sounds right so looks like you have a hole or split in the fuel pick up hose.
They tend to go hard & crack just past where they exit from the tank grommet inside the tank.
Echo make a complete replacement set, both hoses, the filter & grommet which is the easy & safest way to go.
If the fuel line is hard & cracked then the grommet will not be pristine either.
If you are not intending to replace ht grommet then do not remove it as old ones rarely reseal properly.
Use Tygon fuel line, should cost $ 2 to $ 5 for the 6" length you will need.
Just make sure it is the right size.
Supply tube is heavy walled to prevent the tube collapsing onto itself.
Return tube is thin walled.
#14
L
Lawnranger
Since you have had this machine for a LONG time, you will need to perform a few advanced diagnostic tests to verify the integrity of the fuel lines, carburetor and crankcase seals. Using a pressure pump and vacuum pump test each fuel line and the vent itself. Test the fuel lines by plugging one end off and install the pressure/vacuum pump in the other end. Pump up to at least 5psi and watch pressure gauge for any drop. Repeat with vacuum. Test the vent by applying pressure - pump to 5psi - should drop to about 1.5psi and hold. Repeat with vacuum and should not hold any vacuum. I'm not saying this is the problem because nobody knows at this point but you need to test & verify the involved systems.
Since you said the fuel hoses have been replaced not long ago, I don't suspect them but I do test and verify everything. Do not assume the fuel lines are good just because you replaced them not long ago.
Look up Joe Pace on youtube, he has some good instructional videos on how to pressure/vacuum test the entire system. Use "Joe Pace pressure test" in the search box - more than one Joe Pace on youtube
When it comes to chainsaws, sometimes the engine will die when turned on its side and this is usually a leaking crank seal. If you watch all the videos you will learn how to test primary compression and vacuum to verify crankcase integrity. When dealing with an engine this old anything is possible and you need to verify every aspect of the machine.
If you don't have the necessary test tools and/or you can't acquire them, it may be time to retire your blower and purchase new - your decision. You could spend the money on a new carburetor but if that isn't the problem then you are throwing good money after bad.
L
Lawnranger
I have an Echo PB-2100 leaf blower that I've had for a LONG time, she's been good to me.
The fuel lines are in very good condition, replaced not long ago. It has a new fuel filter and spark plug. I've blown air into the lines to see if the lines were cracked or had a pin hole but found no leaks.
Since you have had this machine for a LONG time, you will need to perform a few advanced diagnostic tests to verify the integrity of the fuel lines, carburetor and crankcase seals. Using a pressure pump and vacuum pump test each fuel line and the vent itself. Test the fuel lines by plugging one end off and install the pressure/vacuum pump in the other end. Pump up to at least 5psi and watch pressure gauge for any drop. Repeat with vacuum. Test the vent by applying pressure - pump to 5psi - should drop to about 1.5psi and hold. Repeat with vacuum and should not hold any vacuum. I'm not saying this is the problem because nobody knows at this point but you need to test & verify the involved systems.
Since you said the fuel hoses have been replaced not long ago, I don't suspect them but I do test and verify everything. Do not assume the fuel lines are good just because you replaced them not long ago.
Look up Joe Pace on youtube, he has some good instructional videos on how to pressure/vacuum test the entire system. Use "Joe Pace pressure test" in the search box - more than one Joe Pace on youtube
When it comes to chainsaws, sometimes the engine will die when turned on its side and this is usually a leaking crank seal. If you watch all the videos you will learn how to test primary compression and vacuum to verify crankcase integrity. When dealing with an engine this old anything is possible and you need to verify every aspect of the machine.
If you don't have the necessary test tools and/or you can't acquire them, it may be time to retire your blower and purchase new - your decision. You could spend the money on a new carburetor but if that isn't the problem then you are throwing good money after bad.
#15
A
arch252
A
arch252
I haven't considered all that, and that's a little more advanced than I'm capable of. I have a local small engine shop where I buy a whole lot of parts and I'm pretty sure I could get the to check that for me. Thanks for the info
#17
A
arch252
A
arch252
I have it running fine now and I hate to disappoint but I can't give you clear feedback on exactly what the problem was. I bought the fuel line kit which contained the fuel cap gasket, new primer bulb, new fuel filter, new check valve, new lines and new grommet. That solved the problem. It already had a fairly new primer bulb and a new fuel filter and lines so the problem was apparently a bad seal in the fuel cap, check valve or grommet. I appreciate everyone who chimed in with suggestions. I learned a lot with this. Enough to reaffirm my disdain for two strokes!
#19
L
Lawnranger
L
Lawnranger
Most likely a leaking fuel line. Pressure & vacuum testing the lines would show you the leak. Good for you that the blower is running again.