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Z925A - Won't Re-Start When Hot

#1

T

tjrigario

I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?


#2

Tiger Small Engine

Tiger Small Engine

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?
Click to expand...
The emergency brake on these mowers can get out of adjustment, and not allow mower to start. Had this happen to a customer mower I was working on, and couldn’t figure it out. John Deere dealer resolved the issue. John Deere is very secretive and protective of their technical information and are often different than many other mowers is frustrating and difficult ways.


#3

StarTech

StarTech

Sounds like the ECU is giving problems when hot. Personally you need to determine which system is failing and do a bypass surgery on the ECU wiring. I had fuel solenoid circuit failures, magneto kill circuit failures, and PTO circuit failures on these ECUs and just did bypass surgery on them to return the ZTRs back full operation with all safeties intact.

But the OP will need the wiring schematic and the knowledge of how to do these bypasses.


#4

T

tjrigario

StarTech said:
Sounds like the ECU is giving problems when hot. Personally you need to determine which system is failing and do a bypass surgery on the ECU wiring. I had fuel solenoid circuit failures, magneto kill circuit failures, and PTO circuit failures on these ECUs and just did bypass surgery on them to return the ZTRs back full operation with all safeties intact.

But the OP will need the wiring schematic and the knowledge of how to do these bypasses.
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Interesting. Do the carbureted models have an ECU? I can get it started with a lot of effort, but it backfires like crazy and isn’t happy.


#5

T

tjrigario

Tiger Small Engine said:
The emergency brake on these mowers can get out of adjustment, and not allow mower to start. Had this happen to a customer mower I was working on, and couldn’t figure it out. John Deere dealer resolved the issue. John Deere is very secretive and protective of their technical information and are often different than many other mowers is frustrating and difficult ways.
Click to expand...
I’m skeptical it’s the parking brake as there is still spark, etc. when cranking. I did manage to get my hands on the Kawasaki service manual. The motor has good compression, but I’m going to try a leak down test to make sure everything is good. I’ve heard these motors get pinholes in the head gaskets and leaks can be hard to detect.


#6

StarTech

StarTech

tjrigario said:
Interesting. Do the carbureted models have an ECU? I can get it started with a lot of effort, but it backfires like crazy and isn’t happy.
Click to expand...
Yes but it is not the same as EFI control module.
1680460860360.png


#7

smalltimerpm

smalltimerpm

tjrigario said:
Interesting. Do the carbureted models have an ECU? I can get it started with a lot of effort, but it backfires like crazy and isn’t happy.
Click to expand...
Does this effort mean starting fluid? Is it backfiring thru muffler or carb? If your firing Is correct It does sound like a intake on fuel issue. The fuel plungers are known to get hot and quit working at times and coils are also. Maybe check intake gaskets along with the above I mentioned. Also check fuel passage all the way from tank to carb.


#8

T

tjrigario

smalltimerpm said:
Does this effort mean starting fluid? Is it backfiring thru muffler or carb? If your firing Is correct It does sound like an intake on fuel issue. The fuel plungers are known to get hot and quit working at times and coils are also. Maybe check intake gaskets along with the above I mentioned. Also check fuel passage all the way from tank to carb.
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I don’t typically have to use starting fluid. Just keep cranking and cranking until it goes. Backfiring is coming from the muffler


#9

B

Bertrrr

I'd change spark plugs first - easy to do and might correct your problem - possibly the plug is failing when hot. If it eventually starts that pretty much eliminates the solenoid on the carb.


#10

B

bertsmobile1

Every time the engine revolves it dumps fuel into the muffler if the fuel is not burned in the engine
When the air: fuel ratio is correct for burning at atmospheric pressuree the unburned fuel in the muffler ignites so it goes bang.
This indicates that either you have bad plugs or the timing is way too far retarded


#11

T

tjrigario

Do those carbs have an adjustment setting? I can’t seem to find anything other than an idle screw. My thought was that it was possibly running too rich.


#12

T

tjrigario

Do those carbs have an adjustment screw for mixture? I wasn’t able to find one unless it’s hidden somewhere. The only screw I can find is for idle speed.


#13

S

slomo

tjrigario said:
but it backfires like crazy and isn’t happy.
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Flywheel key inspection time?


#14

T

The Specialist

Is there a row of black relays? If there is, take out the K3 one and shake it. I’m sure you will hear a rattle from it. Put in a new relay and this will solve your problems. That relay controls the fuel shut of game solenoid. I use to work at a JD dealership many years ago and it was this relay that caused the problems


#15

V

VTHOMAS

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?
V
Click to expand...


#16

V

VTHOMAS

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?

Valves need adjustment
Click to expand...


#17

grumpyunk

grumpyunk

My first thought was valve adjustment, but considered two other possibles: lack of spark or lack of fuel.
You can check lack of fuel by squirting some carb cleaner into the intake and trying to start. If it fires on the cleaner, you have a fuel problem. You can check the spark by disconnecting a plug wire, stuffing in a spare plug and laying it on the engine. Crank and see if you get spark. If no spark, viola. Fix that.
Last could be the valves, but generally OHV engines open the valve clearance as the parts and valve seats wear. Flat head engines close the clearance as they wear, causing loose seating and it is worse when hot.
If the clearance is too large, the valve may not open enough to allow a good fuel:air charge that will fire off.
tom


#18

E

Earthquake Landscaping

I had a John Deere that was like that too. The solution? Even when hot, it wanted choke to start. WTF? I never got around to figuring out why. But, same symptom as yours. Full choke on a hot re-start, and it fired up in a heartbeat.


#19

C

cleverlever

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?
Click to expand...
This is a long shot but the Kawasaki has a strange decompression device that could possibly be your problem


#20

B

buckwheat_49

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?
Click to expand...
Have you checked valve lash if it's an overhead valve engine? Could make it hard to start and cause backfire.


#21

S

slomo

tjrigario said:
I've changed the coils and rebuilt the carb.
Click to expand...
With OEM Kawasaki parts or Chinese Ebay/Amazon money wasters? Did you pull the pilot jet and emulsion tube?
tjrigario said:
There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed.
Click to expand...
Please explain the "checked" procedure.


#22

S

sparkyee

Hi, My Kohler KT725 would never start after getting hot. Valve adjustment
cured it for good.


#23

StarTech

StarTech

When hot have you tried attempting after adding a little fuel to carburetor throat? If it does then you probably have a failing fuel solenoid, wiring, or ECU problem. I have seen loose wire terminals to cause this problem.


#24

T

TobyU

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?
Click to expand...
I see where you've changed the coils but you need to do basic diagnosis to see why it isn't starting when this happens.
I assume it's cranking over but not running?
Then the first thing would be to determine whether it's not running because it has too little fuel or too much.
Technically you can claim it has too much fuel if it has no spark because the plugs are wet but regardless that's the things, it either doesn't get enough fuel to run or it could possibly have too much but that should be more obvious or it doesn't have any spark as it's cranking over.
I think the fastest way to determine this is to take the air filter off and spray a little bit of carb cleaner in it when it won't start and see if it hits or even just add some choke.
I have found a lot of Kawasakis that simply don't like to start when they're hot unless you give them choke for 3/4 of a second to a second. Then they fire it up.
If you don't give them choke they will sit there and spend over 8 to 10 times before they fire up sometimes never doing it.

So go back to the basics on square One and see if adding some fuel IE carb cleaner into the intake with the choke open when you spin it over causes it to fire up. If not then you need to check for spark.


#25

H

Hilton43

Sounds like it may be sticking valves due to bad valve guide seals, as the valves heat up and the valve stems swell they will stick due to oiil leaking into the guides. Over tome the rubber seals harden and no lon keep the oil out of the valve guides. Replacement doesn’t require engine disassembly, you can remove the valve covers then rotate the engine until both valves are closed then apply air pressure to the cylinder using an old spark plug with the ceramic broken out and an air fitting welded to it. Then remove the rocket assembly to access the seals.


#26

G

grandpa1007

tjrigario said:
I've got a roughly 11yr old Deere Z925A Zero Turn with a Kawasaki FX751V on it. The motor runs good and strong, but never wants to restart after it's up to operating temperature. I've changed the coils and rebuilt the carb. Neither of those have corrected the problem. There's a fuel shutoff solenoid on the back of the carb that's been checked as well, and it's functioning as designed. I'm officially out of ideas! Has anyone experienced this before?
Click to expand...
Hope you found it. Trouble is definitely caused by ECU module. Every symptom exactly the same that I suffered a year ago on my 651 Kaw. Please don’t destroy the starter by letting it backfire aggressively. Good luck.


#27

G

grandpa1007

ECU is a 10 minute replacement.


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