Export thread

Gas leaking from carb top vent tube

#1

A

arch252

I've got a JD LX279 with liquid cooled 2 cylinder Kawasaki. It was running rough, seemed to be missing if I'm running over rough ground. I noticed some gas coming from the top vent tube. I took the carb off to clean it and stripped the main jet trying to remove it. I replaced the carb with a new one and it is also dripping gas from the top vent tube while running. Obviously not a carb issue. Is this an issue with the fuel pump? Attached a photo of the type of fuel pump it uses.

Attachments





#2

R

Rivets

I wouldn’t blame the pump so fast. To me it’s more likely the float needle and seat not shutting off, allowing to much fuel to enter the carb. I would be removing the carb and check to make sure they are working properly.


#3

A

arch252

I replaced the carb, new carb did the same thing


#4

H

hlw49

Did you replace the fuel line? Could be the fuel line is deteriorated on the inside and parts of it crumbled out and got between the needle and seat. I always replace the fuel filter and line between the filter and carb when replacing carb.


#5

A

arch252

The fuel line from the fuel pump to the carb was stiff but not deteriorated, it was less than 3 years old but I went ahead and replaced it as well.

I can't think of any other cause than the fuel pump but don't know what would cause a fuel pump to do that.


#6

R

Rivets

If fuel is exiting the carb through the vent tube, the float needle is not shutting off fuel to the float bowl. If you purchased a carb off Fleabay it wouldn’t surprise me that it is bad. I have no idea why you would suspect the fuel pump, as it must be working fine if you have excess fuel in the carb.


#7

A

arch252

The OEM carb was leaking fuel out of the top vent tube. I replaced it with an aftermarket carb that did EXACTLY the same thing. Common sense tells me something else caused both carbs to malfunction in the exact same way. I don't know that it's the fuel pump but I don't know what else it could be, that's why I posted.


#8

B

bertsmobile1

I am a bit confused here.
You say fuel is leaking from the carburettor vent tube
I don't see a carburettor vent tube listed in the IPL I have here
And they have not been fitted to mower engines since around 2000 when venting to atmosphere became illegal
So can we have the Kawasaki engine details please ?


#9

StarTech

StarTech

Am128355 (Kawasaki 15003-2653)
Replacement for Kawasaki 4 stroke Carburetor engine Models FD501V-AS03 FD501V-AS05 FD501V-BS02 FD501V-BS03 FD501V-BS05 FD501V-CS02 FD501V-CS05 FD501V-DS05 FD501V-ES05
1662777364506.png

Connect fuel pressure gauge to the output of the fuel pump and report your findings.


#10

A

arch252

I don't even know how to measure the fuel pressure so I know I don't have the equipment for it.

I don't typically diagnose by replacing parts but if the fuel pump is the most likely cause I don't mind spending the $15 on a new one. I just needed to know if a fuel pump could fail to cause excessive fuel to be pumped.


#11

A

arch252

And Bert, it's a FD501V and it is the carb pictured above.


#12

B

bertsmobile1

Thanks Arch,
Not an engine I am familiar with
slip the float bowl off and while holding the float up lightly with you finger, crank the engine to see if the carb can cut the fuel supply off before the float touches the carb.
If you got the carb from AmmoZone or Evilpay then better than average chance it is a defective one bought as scrap from the factory then resold as good to cheapskates
When removed & tipped upside down the carb should hold 7 to 10 psi with just the weight of the float.
Fuel pump carbs usually have a slightly longer needle than identical looking gravity feed carbs
I get 1 or 2 a month through the gate wanting me to find the "mystery" fault they can not even after they have replaced everything
And I find the new carb is defective
I have even had more than one person supply me with multiple replacements for the defective carb that were all defective because were sure my $ 60 carb was just one of their $ 10 carbs with a $ 50 mark up. ( they get charged actual hours so by the time they find a good one they have racked up a hundred or more in labour )


#13

StarTech

StarTech

arch252 said:
I don't even know how to measure the fuel pressure so I know I don't have the equipment for it.

I don't typically diagnose by replacing parts but if the fuel pump is the most likely cause I don't mind spending the $15 on a new one. I just needed to know if a fuel pump could fail to cause excessive fuel to be pumped.
Click to expand...
You use a fuel pressure gauge. Max output pressure should be under 10 psi as to not to over pressurize the fuel line at the carburetor.

And as Bert said even new carbs can be defective. I had one OEM carburetor this year that failed to hold off the fuel pressure on a gravity fed system. The distributor replaced it free of charge under warranty. With after market they may be supplying a gravity flow version and not a pump fed version.

BTW the Kawasaki OEM fuel here lists for $81.50. And JD brick and mortar shops asking $185.40. So that $15 pump is an aftermarket clone pump.

This one is the online priced JD pump.
1662803247225.png


#14

A

arch252

Thanks Bert, I'll check that as you described. I just find it extremely unlikely that both the OEM carb AND the replacement carb would both fail in exactly the same way. That would be quite the coincidence and I have a hard time accepting coincindences.


#15

R

Rivets

The basic FD501V engine has at least 4 different carb which can be use, depending on the Spec number. Could very easily have the wrong carb as they all look the same.


#16

StarTech

StarTech

arch252 said:
Thanks Bert, I'll check that as you described. I just find it extremely unlikely that both the OEM carb AND the replacement carb would both fail in exactly the same way. That would be quite the coincidence and I have a hard time accepting coincindences.
Click to expand...
Believe it. It is possible as I had it just happen about two months ago here with a MTD P90 engine. And both carburetors were OEM one at that.


#17

S

slomo

OP seems to have a good answer book. (y)

1.Used OEM carb leaking fuel, I get it. Remedy the needle and seat.
2.New "UNTESTED" Chinese carb, definitely understand slash expected it. All carbs should be pressure tested.
3.Going by the most likely cause is getting you nowhere.

Story went from a leaky carb to a fuel pump issue. Still not cutting grass.


#18



Deleted member 97405

I have encountered this exact issue numerous times over the years. What happens, due to age, the fuel pump begins to deteriorate internally, even though it still works! Since the pump is after the fuel filter, the particles go straight to the carb and block the inlet needle open. You can clean as best as you want, but you'll never get all the particles, and more will come as the pump continues to deteriorate. You will have to replace the fuel line from the tank all the way to the carb as well as install a new fuel pump. Take your new carb off and remove the needle and float. Remove any debris from the bowl, needle, and inlet tube (the part your fuel line connects to) This is the ONLY way to completely rid the system of the problem. Blame ethanol gas. It dries out the older fuel system components over time. Once updated, you should be ok with ethanol fuel again unless you use all Chinese parts. Then the issue will come back eventually because they use inferior rubber parts, which ethanol will attack. Ethanol will also attack plastic parts, i.e. floats, in Chinese carbs as well. Just FYI. Ask my neighbor. Fuel ate right through his float in 6 months. Fix it right if you plan on keeping it. It will be expensive, but it beats spending $4000 or more for a new tractor. For comparison, the current X350 or X380 is the replacement for your tractor if you want to get some prices. No point in scrapping it, just fix it right, and let Amazon keep their Chinese junk. You should be able to find a Kawasaki carb and fuel pump versus spending Deere's stupid high prices. I have done this repair more than I can count on these machines. Ethanol is the problem, politicians enact it, we pay for it. But I digress....Hope this helps!


#19

A

arch252

Will1988 said:
I have encountered this exact issue numerous times over the years. What happens, due to age, the fuel pump begins to deteriorate internally, even though it still works! Since the pump is after the fuel filter, the particles go straight to the carb and block the inlet needle open. You can clean as best as you want, but you'll never get all the particles, and more will come as the pump continues to deteriorate. You will have to replace the fuel line from the tank all the way to the carb as well as install a new fuel pump. Take your new carb off and remove the needle and float. Remove any debris from the bowl, needle, and inlet tube (the part your fuel line connects to) This is the ONLY way to completely rid the system of the problem. Blame ethanol gas. It dries out the older fuel system components over time. Once updated, you should be ok with ethanol fuel again unless you use all Chinese parts. Then the issue will come back eventually because they use inferior rubber parts, which ethanol will attack. Ethanol will also attack plastic parts, i.e. floats, in Chinese carbs as well. Just FYI. Ask my neighbor. Fuel ate right through his float in 6 months. Fix it right if you plan on keeping it. It will be expensive, but it beats spending $4000 or more for a new tractor. For comparison, the current X350 or X380 is the replacement for your tractor if you want to get some prices. No point in scrapping it, just fix it right, and let Amazon keep their Chinese junk. You should be able to find a Kawasaki carb and fuel pump versus spending Deere's stupid high prices. I have done this repair more than I can count on these machines. Ethanol is the problem, politicians enact it, we pay for it. But I digress....Hope this helps!
Click to expand...


#20

A

arch252

I replaced the fuel pump, no change. I dropped the bowl on the carb, bowl was clean. Checked the float, held it level with my finger and it cut off the fuel supply. I went ahead and removed the float and needle to remove any possible debris. Put it back together. Still pumping A LOT of fuel out of the top vent while it's running, worse than before.

So to summarize everything so far: mower was running rough, had to keep it choked to keep it running. I noticed some fuel coming from the OEM carb top vent tube. I screwed up the jet trying to remove it while cleaning the carb. I replaced the carb with a new aftermarket. Same thing, leaking gas from the top vent tube while running. I replaced the OEM fuel pump with a new aftermarket, no change, still pumping fuel, even stronger now, out of the vent tube.


#21



Deleted member 97405

The reason the fuel is coming out the vent tube is because the bowl of the carb is overflowing. The vent tube is a port that goes directly to the bowl of the carb. When the bowl overflows, the fuel pushes out the vent tube rather than all going into the engine intake. You definitely have an issue with that carb inlet. The fuel pump is a low pressure pump and will not overpower the float needle unless there is a problem there, i.e debris in the inlet. When my sister's tractor had the same issue, I had to replace all the parts listed above. All it takes is a microscopic piece of debris to keep that inlet needle from properly stopping the flow of fuel. That ethanol is crap, and if your system is contaminated, the only way to correctly fix it is to replace all the parts. There is no way to thoroughly flush a contaminated fuel pump unless you want to take that chance and have to pull your carb many times to clean it. On a side note, I have had Chinese carbs leak internally right out of the box. Could be you just have a carb issue now. The metal the carb is made out of is porous, meaning gas will find its way through it. The carbs are coated with a sealer invisible to the naked eye. This is why you don't soak a carb in solution too long because it eats that coating off. Chinese carbs are inferior, and the coating isn't as good as OEM, therefore, it may be leaking for that reason as well. Over 20+ years, you see a lot of things, but with this system, I've only successfully fixed it by following the post I posted above. Otherwise, this issue could plague you until you're sick of the tractor. Good luck.


#22

Hammermechanicman

Hammermechanicman

If you can do a cylinder leakdown test. Especially check intake valves for sealing properly. A bad intake valve on a twin can cause poor running and fuel to be spit out of the carb.


#23



Deleted member 97405

Hammermechanicman said:
If you can do a cylinder leakdown test. Especially check intake valves for sealing properly. A bad intake valve on a twin can cause poor running and fuel to be spit out of the carb.
Click to expand...
This will cause fuel to spit out the throat of the carb and soak the air filter. He's not having that issue. His fuel is coming out the vent tube. Good input though.


#24

PTmowerMech

PTmowerMech

Well, this thread didn't solve anything. I'm having the same issue. Everything new, except the fuel pump. I get what @Rivets said, if the carb is getting fuel, then the pump must be OK.
But then again, this is a mechanical fuel pump and since this vent tube apparently goes straight though from the float bowl to the vent, then I can see how the pump over over-pump.

Some guy on a video said he adjusted his float so that it didn't drop down as far. Which made no sense to me. I think he just got lucky. But did say that he still has the same problem with the new carb. And that's the float he adjusted. Then it shows him mowing and it running and cutting fine (for like 10 minutes)


#25

PTmowerMech

PTmowerMech

Problem solved (for now). I did a few things, so I'm not quite sure what actually solved the problem. But here's what I did.

1. Removed the new carb and cleaned it.
2. Used the float from the old carb. It seemed to sit as level. But when you turn it right side up, it didn't drop as far. So my thinking is, the needle could've been binding and not closing all the way. This one has that wire hanger that keeps it attached to the float.
3. Since the fuel pump was old, I put a filter between it and the carb, just to see if there was any thing coming from the pump. And in deed there was. After about 20 minutes of running it, there were a few small specks of something caught in the filter. Now there's a filter before the pump and one after.
4. I put a piece of 2 cycle fuel line from the vent down through the frame, just in case it started overflowing again, it wouldn't be close to the muffler.

After all that, and getting everything back on, the engine surged real bad. So I opened up the mixture screw and leveled it out. I did have some trouble getting the choke adjusted, But I think I got that working now.
And lastly, I set the high idle about about 3700 RPM.

So if anyone else has this problem, and used an amazon carb ($25 vs $300). and it still does it, you might try using the old float and two filters.


#26

S

slomo

From what I've seen on Chinese carbs, if you go through the parts, make sure they do what they are supposed to do. And like you did substitute parts when needed. Most of the time you can get them to work if they don't work out of the box.


#27

PTmowerMech

PTmowerMech

slomo said:
From what I've seen on Chinese carbs, if you go through the parts, make sure they do what they are supposed to do. And like you did substitute parts when needed. Most of the time you can get them to work if they don't work out of the box.
Click to expand...

Right.

It was in all the forums I read on this carburetor, with so many people trying so many different things. The one thing that stuck in my head was a video of some guy who I could barely understand, who didn't even know what the parts of the carburetor was. He mentioned something about bending the ear of the float so that it didn't drop down too far. At first, that made no sense, because I was thinking that it didn't matter how far the float dropped, as long as it came back up and sealed the needle when the bowl was full.
But then another guy (I can't believe I'm about to repeat this).... He took some aluminum polish on a cue tip, put the cue tip in a drill and polished the inside wall of where the needle rides. This, believe it or not, made his needle slide in and out very easily. It's probably made the ID a tiny bit bigger also.

Add those things with what @Rivets (and others) said about the only thing that could be causing the problem is the needle not seating, and KA BOOM,


#28

B

bertsmobile1

If you are catching crud after the fuel filter then some thing between it and the carb is on its way out
As you know you do not need much crud under the float needle to cause it not to seat
A little tool you might consider making is a dead solenoid , guts removed and piece of plastic tube attached
Tie the tube off so it is upright then you can see what level the float needle actually allows the bowl to fill to .
It is a std tool for British bike techs who try to tune Amal concentric carbs which seem t come from the factory with random float heights


#29

PTmowerMech

PTmowerMech

slomo said:
From what I've seen on Chinese carbs, if you go through the parts, make sure they do what they are supposed to do. And like you did substitute parts when needed. Most of the time you can get them to work if they don't work out of the box.
Click to expand...

I'm in the process of building me another work bench, that's going to include another carburetor test cradle. Where I can hang a carb that's attached to a fuel tank, to check it for leaks or overflow before installing it. Those are pretty handy with todays amazon carbs.
I gotta say, this one, like most others I've gotten from Amazon have been OK. I know they get a bad rap, but honestly I not gotten a bad 4 cycle one in a while.
The last 2cycle carb I bought, I thought was junk. But it turned out to be the throttle cable was not routed right.


Footer Links 1

Top