Need help with periodic engine slowdown fault on my GX335. After mowing for 1 hr. + each of last few weeks with PowerFlow attached, engine suddenly slowed & nearly stalled. Dis-engaged PTO by which time engine returned to full throttle speed. Mowed for another ｽ+ hr. & engine again slowed to stall speed. Left PTO engaged & after running at near stall speed for 5-10 seconds engine returned to full throttle speed. A 3rd generation JD dealer service mgr. feels it痴 a fuel sys. problem. He suggested several causes including blocked fuel cap, & partially blocked carb. vent tube. I checked that fuel flows well from pump outlet (orig. pump). I致e now installed a new fuel cap, all new fuel hoses from tank to carb.; new filter; installed new carb. clear plastic vent tube. Had installed new plugs in Oct. ?0; re-checked condition & gap. Have a new fuel pump I can install. Anyone had this happen? What am I missing guys?
GX335 engine slows to stall speed several times during a 3 hour mowing
- Thread starter rlhatejd
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beenthere
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Apparently just missing the real problem. Nothing to offer with the descriptive explanation so far.
Drop it off at the dealer to let the mechanics check it out, or keep zeroing in on the conditions that seem to cause it to fail, and those conditions where it does not fail.
Like, does it do this with just the powerflow attached, or not?
Sounds like a fuel problem to me too, but that will have to be checked out by some tests (or throw in the fuel pump and see if that helps).
Good luck.
Hating the JD prolly doesn't help coming up with a solution.
Drop it off at the dealer to let the mechanics check it out, or keep zeroing in on the conditions that seem to cause it to fail, and those conditions where it does not fail.
Like, does it do this with just the powerflow attached, or not?
Sounds like a fuel problem to me too, but that will have to be checked out by some tests (or throw in the fuel pump and see if that helps).
Good luck.
Hating the JD prolly doesn't help coming up with a solution.
RandyT
Elite Member
could there be a bearing either on the deck or the grass collector seizing causing the engine to pull down and then return to speed later.
Was your mower stored over the winter in an area that spiders could access? I have have several starting and running problems due to a tiny spider web blocking a fuel line, carburetor port or air intake.
Most engines require air, fuel, lubrication and spark to operate properly. If any of those are missing or not at the correct mix, problems ensue.
With the fuel system being re-built, that should have eliminated any fuel related problem. Have you check the air intake and air filter "duct work"?
Most engines require air, fuel, lubrication and spark to operate properly. If any of those are missing or not at the correct mix, problems ensue.
With the fuel system being re-built, that should have eliminated any fuel related problem. Have you check the air intake and air filter "duct work"?
TonyMcD痴 ref. to a JD air filter revision is a possibility. My JD service manager suggested I make sure I have the correct filter; I知 checking on this possibility on Mon. But, I have no black smoke problem as JD says associated with filter rev. The only part of air sys. I haven't checked is the breather hose. That, a new fuel pump & vac. hose for the pump are next.
For the guys who think I hate JD, not true. My username of rlhatejd is simply my name & initials + jd for John Deere; make sense guys?
For the guys who think I hate JD, not true. My username of rlhatejd is simply my name & initials + jd for John Deere; make sense guys?
irwin
Veteran Member
I've had several lawn tractors that would do that when the fuel fill cap vent was plugged up... looks like you've covered the normal issues... hope you get it figured out... have you loosened the new cap when it happens? what the heck, it might not be venting properly.
Regarding my GX335 engine problem, has anyone watched the flow of fuel through their see-through filters? I don't understand why only the lower 1/4 of the filter has fuel flowing when filter is level. And this is after installing all new fuel hoses & new fuel cap. If I am getting vapor lock occasionally, how do I solve that? Meanwhile, will try the suggestions offered so far, including loosening the new fuel cap. Many thanks from PA.
Egon
Epic Contributor
Start looking at the inside
of tank for any restrictions at the outlet. Then just follow the fuel system step by step.
With only 1/4 full showing on the filter I'd suggest there some type of blockage between the tank and filter.
Now don't go away mad if the suggestion is in error.
of tank for any restrictions at the outlet. Then just follow the fuel system step by step.
With only 1/4 full showing on the filter I'd suggest there some type of blockage between the tank and filter.
Now don't go away mad if the suggestion is in error.
aczlan
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Start looking at the inside
of tank for any restrictions at the outlet. Then just follow the fuel system step by step.
With only 1/4 full showing on the filter I'd suggest there some type of blockage between the tank and filter.
I agree. Pull the line from the upstream side of the filter, see how fast it flows out and blow backwards in the the line to see if that makes it flow out faster. Could be some crud in the tank outlet.
Aaron Z
tomd999
Platinum Member
Hi,
Since you are already trying the fuel cap trick, I'll give you some other ideas/things to check.
1) Altitude: If you live anywhere that's not close to sea level, your jetting could use some adjusting. When the engine pulls down, see if choking it slightly causes it to get back on govenor quicker, if it does, your lean which would cause the engine to run hotter than intended.
2) The fuel filter being 1/4 full is not an issue, don't worry about it.
3) When the engine is pulled down is the exhaust black while it tries to recover? What color are the sparkplugs? Is the engine hard to start back up after it stalls or is it harder to start when it's stone cold?
4) Is the engine bolted down tight? A lose engine vibrates more and can cause the fuel in the float bowl to foam, when that happens the carb cannot meter the ratio properly and the mixure will go very lean. Check the bolts
5) How many hours on the engine since you last pulled the covers off and cleaned out the chaffe? Most air cooled engine makers say at least once a mowing season, more in dusty conditions. If this is a Kawasaki or BS Vangard V-twin, pay close attention to the area between the cylinders, they collect a lot of debris there.
6) Take the hood off. Nothing like letting the engine have free and open access to the air. Some older lawn tractors did not have enough air flow with the hood on, simply taking it off solved the issues.
7)How old is the fuel? If your using winter blend fuel in hot temps, with a hot engine, you could be boiling off in the floatboal and causing the same condition as frothing/foaming fuel noted above. Get some fresh fuel and see. Also, fuel stabilizer does effect how the fuel performs at high temps, if your fuel is heavly dosed with it, that may be part of the issue.
Honestly, anyone with gasoline powered equipment should be using VP racing fuels small engine fuel(SEF), it contains no on the road EPA additives and does make a difference in the performance of these small engines. Small Engine Fuel (SEF?) From VP Racing Fuels
Since this only happens when the engine has been running for some time, then happens with greater frequency the longer it is run, I would look to cooling and venting being a large part of this issue.
Of course it's been 30 years since I ran a small engine repair shop but these are the steps I would take if you came in and told me everything you have already tried.
Tom
Afterthought: Is the powerflow new to the picture with this mower? If it is an additional load, and the engine isn't at 100% either from hours/wear or improper setup, the additional load may be more than it's able to output and it's not able to catchup to the load. Mowers should be run at about 75-80% of capacity, the small gasoline engines don't have the torque to catch up like a Diesel does.
Since you are already trying the fuel cap trick, I'll give you some other ideas/things to check.
1) Altitude: If you live anywhere that's not close to sea level, your jetting could use some adjusting. When the engine pulls down, see if choking it slightly causes it to get back on govenor quicker, if it does, your lean which would cause the engine to run hotter than intended.
2) The fuel filter being 1/4 full is not an issue, don't worry about it.
3) When the engine is pulled down is the exhaust black while it tries to recover? What color are the sparkplugs? Is the engine hard to start back up after it stalls or is it harder to start when it's stone cold?
4) Is the engine bolted down tight? A lose engine vibrates more and can cause the fuel in the float bowl to foam, when that happens the carb cannot meter the ratio properly and the mixure will go very lean. Check the bolts
5) How many hours on the engine since you last pulled the covers off and cleaned out the chaffe? Most air cooled engine makers say at least once a mowing season, more in dusty conditions. If this is a Kawasaki or BS Vangard V-twin, pay close attention to the area between the cylinders, they collect a lot of debris there.
6) Take the hood off. Nothing like letting the engine have free and open access to the air. Some older lawn tractors did not have enough air flow with the hood on, simply taking it off solved the issues.
7)How old is the fuel? If your using winter blend fuel in hot temps, with a hot engine, you could be boiling off in the floatboal and causing the same condition as frothing/foaming fuel noted above. Get some fresh fuel and see. Also, fuel stabilizer does effect how the fuel performs at high temps, if your fuel is heavly dosed with it, that may be part of the issue.
Honestly, anyone with gasoline powered equipment should be using VP racing fuels small engine fuel(SEF), it contains no on the road EPA additives and does make a difference in the performance of these small engines. Small Engine Fuel (SEF?) From VP Racing Fuels
Since this only happens when the engine has been running for some time, then happens with greater frequency the longer it is run, I would look to cooling and venting being a large part of this issue.
Of course it's been 30 years since I ran a small engine repair shop but these are the steps I would take if you came in and told me everything you have already tried.
Tom
Afterthought: Is the powerflow new to the picture with this mower? If it is an additional load, and the engine isn't at 100% either from hours/wear or improper setup, the additional load may be more than it's able to output and it's not able to catchup to the load. Mowers should be run at about 75-80% of capacity, the small gasoline engines don't have the torque to catch up like a Diesel does.
Last edited:
Tom:
The only thing I haven稚 tried until reading your suggestions & questions is running with the new fuel cap loose, replacing the fuel pump, & checking the breather hose. With new fuel hoses from tank to pump to carb, I also blew air through the fuel tank quil tube & no dirt entered tank. No black smoke has appeared & engine has actually only quit once; all other incidents have been slowdown to stall speed for about 5-10 sec. & then return to full throttle speed. I experienced no hard starting problems. Spark plugs are dark gray (if I recall; checked them 3 weeks ago); no soot deposits & dry. I do need to use the choke trick during the stall speed mode (also suggested by JD serv. mgr). I will check the engine mount bolts & your comments regarding cleaning out the chaff certainly bear action; at 624 hrs., this has never been done! I am using fuel recently drawn from local station along with StatTron enzyme fuel treatment (1 oz to 3 gal) to counter Ethanol problems. The PowerFlow has been used since the 335 was new. Also, I have had the engine slow down to stall speed (but not quit) with mower, with mower & PowerFlow, & even several times with no load.
Meanwhile, my thanks to others who have made suggestions, some of which I致e already tried. We will keep at this until we solve it. The help of all is much appreciated. ~Dick
The only thing I haven稚 tried until reading your suggestions & questions is running with the new fuel cap loose, replacing the fuel pump, & checking the breather hose. With new fuel hoses from tank to pump to carb, I also blew air through the fuel tank quil tube & no dirt entered tank. No black smoke has appeared & engine has actually only quit once; all other incidents have been slowdown to stall speed for about 5-10 sec. & then return to full throttle speed. I experienced no hard starting problems. Spark plugs are dark gray (if I recall; checked them 3 weeks ago); no soot deposits & dry. I do need to use the choke trick during the stall speed mode (also suggested by JD serv. mgr). I will check the engine mount bolts & your comments regarding cleaning out the chaff certainly bear action; at 624 hrs., this has never been done! I am using fuel recently drawn from local station along with StatTron enzyme fuel treatment (1 oz to 3 gal) to counter Ethanol problems. The PowerFlow has been used since the 335 was new. Also, I have had the engine slow down to stall speed (but not quit) with mower, with mower & PowerFlow, & even several times with no load.
Meanwhile, my thanks to others who have made suggestions, some of which I致e already tried. We will keep at this until we solve it. The help of all is much appreciated. ~Dick
Using the choke indicates the fuel mixture is too lean at times and you need more gas. Still think it is a fuel flow problem.
Just for grins and giggles, a friend of mine had idling problems with his sears 25 hp lawn tractor, so we switched to bosh 3 electrode plugs in the same heat range and fixed the problem.
Just for grins and giggles, a friend of mine had idling problems with his sears 25 hp lawn tractor, so we switched to bosh 3 electrode plugs in the same heat range and fixed the problem.
KennedyDiesel
Veteran Member
Your engine requires 2 key ingredients to run. Air and fuel. To ignite this it needs compression and spark. The ignition will not cause it to slow down randomly, only loss of air or fuel flow will do this. It sounds like it's lacking fuel. Be it fuel quality, or quantity.
Fuel quality
Vapor lock/boiling gas
Plugged filter
Plugged tank vent
Fuel quality
Vapor lock/boiling gas
Plugged filter
Plugged tank vent
I've been having a similar issue. Only occurs while mower is engaged. Snowblower in the winter seems to work find. JD has had it 3 times and finally are saying carb needs replaced. I was curious if others had found this fixed the problem before I drop the money for that.
Here are some similar links:
