John Deere 727a

[emcm80]

Got a 2007 John Deere 727a 26hp Kawasaki engine.

In the last 18 months I've had a brand new carburetor put on, completely removed, cleaned the fuel tank, fuel lines, etc. all done by the local JD service folks.

I took the mower in because it kept dying in the middle of cutting.

After all of that and the several hundreds of $$, the problem still exists and I'm sick of the guys at the service area saying nothing is wrong.

The mower seems to run fine the first 5 minutes, but once it gets warm, the problem starts happening.

The engine bogs down and will die. If I pull back on the steering arms to nearly a stop, the mower will come back up to full rpms and I can keep cutting, but just for a few seconds till it bogs down again.

Extremely frustrated with the machine. I'm guessing there's some kind of electrical issue or something that gets effected when the mower gets warm.

Any ideas?

 

[Exracer]

Got a 2007 John Deere 727a 26hp Kawasaki engine.

In the last 18 months I've had a brand new carburetor put on, completely removed, cleaned the fuel tank, fuel lines, etc. all done by the local JD service folks.

I took the mower in because it kept dying in the middle of cutting.

After all of that and the several hundreds of $$, the problem still exists and I'm sick of the guys at the service area saying nothing is wrong.

The mower seems to run fine the first 5 minutes, but once it gets warm, the problem starts happening.

The engine bogs down and will die. If I pull back on the steering arms to nearly a stop, the mower will come back up to full rpms and I can keep cutting, but just for a few seconds till it bogs down again.

Extremely frustrated with the machine. I'm guessing there's some kind of electrical issue or something that gets effected when the mower gets warm.

Any ideas?

I would change both ignition coils and set clearance to .012 and bet your problem is over. Probably around $120 for both coils. Seen this before. When it drops a cylinder you loose have of your horsepower and the above description happens.

 

[rejiii]

Got a 2007 John Deere 727a 26hp Kawasaki engine.

In the last 18 months I've had a brand new carburetor put on, completely removed, cleaned the fuel tank, fuel lines, etc. all done by the local JD service folks.

I took the mower in because it kept dying in the middle of cutting.

After all of that and the several hundreds of $$, the problem still exists and I'm sick of the guys at the service area saying nothing is wrong.

The mower seems to run fine the first 5 minutes, but once it gets warm, the problem starts happening.

The engine bogs down and will die. If I pull back on the steering arms to nearly a stop, the mower will come back up to full rpms and I can keep cutting, but just for a few seconds till it bogs down again.

Extremely frustrated with the machine. I'm guessing there's some kind of electrical issue or something that gets effected when the mower gets warm.

Any ideas?

I have the exact same problem, with a 727A (than ran perfectly for 20 years) and HAVE replaced the coils. Nothing helped except an electric fuel pump that quit after 2 days (thanks China). I have noticed that the fuel filter (replaced several times) never fills, even when the mower is idling or running at full throttle. I have ordered another electric fuel pump (oem) so I will keep everyone informed. Note I have done everything that emcm80 had done and it didn't work for me either. Hopefully the fuel filter not filling will lead me to the correct diagnosis.

UPDATE: After the Chinese electric fuel pump failed, I installed a Quantum Fuel Systems HFP-180 electric fuel pump that is compatible with JD 777 ZT mower. It is much more robust that the other pump, and I have used it several days in very thick pasture grass and there have been no problems with fuel delivery as with original JD vacuum fuel pump. Although the mounting holes do not match exactly, I was able to install it with very little difficulty. I did use rubber grommets between the mounting plate and fuel pump to reduce vibrations caused by my rugged mowing conditions (I tend to use it as a self-propelled bush hog.). I will be back with further updates as I gain more experience with the new setup.

June 16, 2022: I have mowed 20+ acres of grass of various density with no problem using the Quantum pump. Since I use it every week, I am going to stick with this as my solution until this winter when I can experiment with the vacuum which drives the stock JD fuel pump. Something tells me it does not supply sufficient vacuum when under heavy load which is where engine stalls every time using the JD vacuum operated fuel pump. Will keep everyone up to date when I get a chance to look at it again.

If anyone is knowledgeable about engine vacuum I'd love to hear from you.

It's now October 2022 and the electric fuel pump did the trick for the whole summer, regardless of the grass height/thickness.

 

[bertsmobile1]

If you bought the fuel filter of ebay / amazon it could very well have been a defective part rejected at the factory then sold as scrap wholesale after which it gets resold into the second line parts system as was the case with the fuel pump so the blame for it belongs to Americans ( Amazon & Ebay ) not the Chinese.
However this will not be the case with the parts the dealers fit they all would have been certified as good before the dealers get their hands on them .
It is also not a problem with parts bought through Alibaba where they will not allow defective parts to be sold as good .

Fuel filters come in 2 varieties
One has the inlet & outlet holes flush with the case.
On the other the outlet is via a tube than extends almost to the opposite end of element .
The latter type will trap air between the case & the outlet end of the tube so they will almost never seem to fill completely yet flow more than enough to keep the float bowl full.
Remember the hole in the main jet is 0.020" the hole in the fuel pipe is .250" .

When faced with this sort of a problem it is always useful to separate fuel problems from ignition problems
Foe me, I fit a pair of red in line spark testers then go mow
When the engine starts to faulter I watch them by kneeling on the seat and mowing backwards
IF the testers illuminate as usual while the engine is dieing then I assume the problem is fuel related
If the testers flash erratically then I can assume it is an ignition problem.
I also have some short bolts I use to replace the fuel solenoid in the carb to eliminate it

 

[rejiii]

If you bought the fuel filter of ebay / amazon it could very well have been a defective part rejected at the factory then sold as scrap wholesale after which it gets resold into the second line parts system as was the case with the fuel pump so the blame for it belongs to Americans ( Amazon & Ebay ) not the Chinese.
However this will not be the case with the parts the dealers fit they all would have been certified as good before the dealers get their hands on them .
It is also not a problem with parts bought through Alibaba where they will not allow defective parts to be sold as good .

Fuel filters come in 2 varieties
One has the inlet & outlet holes flush with the case.
On the other the outlet is via a tube than extends almost to the opposite end of element .
The latter type will trap air between the case & the outlet end of the tube so they will almost never seem to fill completely yet flow more than enough to keep the float bowl full.
Remember the hole in the main jet is 0.020" the hole in the fuel pipe is .250" .

When faced with this sort of a problem it is always useful to separate fuel problems from ignition problems
Foe me, I fit a pair of red in line spark testers then go mow
When the engine starts to faulter I watch them by kneeling on the seat and mowing backwards
IF the testers illuminate as usual while the engine is dieing then I assume the problem is fuel related
If the testers flash erratically then I can assume it is an ignition problem.
I also have some short bolts I use to replace the fuel solenoid in the carb to eliminate it

Thanks for your reply. After I fitted the Chinese pump it immediately failed after 1 day or so of mowing. It was definitely a cheap unit unfit for rugged use regardless of its history.

As for the electrical, I did a complete diagnosis (I'm a EE.) to eliminate it as the cause. I even replaced both coils as a precautionary measure. My final diagnosis was the problem was definitely with fuel delivery during heavy load (It would run for hours at idle or low load without a hitch.), not ignition issues. Whether due to vapor lock, low vacuum from the engine, fuel pump or other fuel matters I cannot say. I can say it was not due to fuel lines, valves, pumps, fuel filters, and carb. And yes I did drain the gas tank and look for debris, water, etc.

Thanks to all of you that have responded to my issue.

 

[bertsmobile1]

The carburettor has 2 circuits, the idle circuit & the main jet
Despite being called idle , the low speed circuit supplies all the fuel till you turn the blades on or go up a big hill .
For far less than the price of a single magneto coil you can get a HF leak down tester .
While not the best bit of kit they are good enough to find leaking head gaskets and valves that don't seal properly.
Even an engine with a burned exhaust valve and crud stuck under the inlet will suck fuel through the main jet .

Usually your symptoms are a sign of a build up of floating debris in the fuel tank
While there is little flow it floats around happily but when there is heavy demand it gets sucked into the fuel outlet where it forms a plug reducing the fuel flow.
The instant the flow stops , it floats away again .
IT took me a long while to get my head around that one.
The test for this . or confirmation rather , is to hook up a temporary fuel tank then go mow problem goes away then you have confirmed a dirty tank
Grass clippings are heavier that fuel so they sink, but over time the water gets replaced by fuel so the grass clippings are almost the same weight as the fuel so they float around in suspension & are very hard to see because the petrol bleaches the colour out of the clippings .
So do a couple of mows and note how long it takes to happen.
The instant it does , whip the fuel line off the engine & crank it
The fuel flow should be the same as when it was cold .
Second test is to pull the fuel line off at the intake side of the fuel pump & blow back into the tank .
If this was difficult to do and the mower ran fine for about the same time afterwards then again floating debris becomes the prime suspect .
Final confirmation is the substitute fuel tank but it must hold enough fuel to run the mower for longer than the mean time between failures .
Note the fuel pump has a check valve on the output side and good ones like the metal Mikunis have check valves on both inlet & outlet so don't try to blow from the carb backwards unless you can blow up rubber gloves to the size of footballs .