FT730v-efi runs 12-15 minutes , then starts missing

[Bmp4510]

I have a 2022 Scag Turf Tiger, 220hrs, with a Kawasaki FT730v-efi engine. Trying to fix for my neighbor. The original problem was he dumped some horrible fuel in it. Took a while to track it down, finally used a separate fuel tank with new fuel and she ran good. In the attempt to fix it prior to discovering the fuel issue, the fuel pressure pump was replaced, fuel filter, spark plugs, air cleaner was cleaned.

After emptying the gas tanks, flushed and vacuumed out three times, the machine ran well. For 15 minutes, the the motor stumbles horribly. Reducing throttle to idle and the engine appears to run normal. To repair this issue, new crank position sensor, new coils, valve lash checked, flywheel key checked, tried running with engine temperature sensor disconnected, tried with charcoal canisters removed from fuel system. If you let the mower sit for 20-30 minutes, she fires up, runs great and again in 12-15 minutes with WOT it will stumble and miss. I gave up mow testing, I just test the motor with the mower in park at WOT. Outside temperature is 75-80 degrees.

i have access the Kawasaki computer interface and software. The engine is not throwing codes. I can turn off #1 or #2 spark plugs, and #1 and #2 injectors. When the motor is missing, turning off either spark plugs (actually the coils) the motor runs even worse. Oddly when I turn off either of the injectors, the motor actually picks up some rpm, but is still missing. Engine temperature is still within normal range. I talked to Kawasaki tech support, and still have not received a good answer.

I’m at a loss and would greatly appreciate any advice or assistance with this issue.

 

[slomo]

I'm not a mower EFI xpert. I would stop buying new parts and TEST what you already have. All those new parts are suspect till you confirm they actually work.

From what you wrote, I would guess you still have some trash in the fuel system.

Was the fuel can an old style with maybe an open top or open spout? If so probably had a bunch of trash/water in the bottom of the fuel can. I would get a new style spout or new can. Fuel stays fresher and keeps most of the dirt out.

I would remove the fuel line AT the injector. Key on should fire the fuel pump. Drain a bunch of fuel into a glass jar. Should have a forceful flow and hopefully no trash/water. Flush out all injector lines closest to the injector as possible.

 

[Bmp4510]

I'm not a mower EFI xpert. I would stop buying new parts and TEST what you already have. All those new parts are suspect till you confirm they actually work.

From what you wrote, I would guess you still have some trash in the fuel system.

Was the fuel can an old style with maybe an open top or open spout? If so probably had a bunch of trash/water in the bottom of the fuel can. I would get a new style spout or new can. Fuel stays fresher and keeps most of the dirt out.

I would remove the fuel line AT the injector. Key on should fire the fuel pump. Drain a bunch of fuel into a glass jar. Should have a forceful flow and hopefully no trash/water. Flush out all injector lines closest to the injector as possible.

Thanks for the reply. Gas tanks have been flushed twice and vacuumed out. Motor has run over 2 hours since bad fuel cleaned from system. I can remotely fire the injection pump using the computer, and both injectors fire fine. For testing I use the $30 gallon gas from Home Depot. Both press pump and pickup pump meet specifications, and with the expensive gas are spotless clean running through the pumps.

 

[slomo]

Dirty injector?

Okay got to ask? Is this water or air cooled? If no radiator, have you cleaned the cooling fins?

Spark strong all the time or do you lose spark?

 

[slomo]

I can remotely fire the injection pump using the computer, and both injectors fire fine.

What does the spray pattern look like?

 

[Bmp4510]

What does the spray pattern look like?

The motor is air cooled. Find are spotless clean, especially after pulling flywheel to check the key to make sure timing was right.

The spray pattern is just a tiny squirt, and that’s when it’s cold. Not like the ads for injection cleaner's. And oddly as I wrote, when the motor gets warm, with a pc hooked up, I can see the engine temperature, and it’s fine.. I’ve also pulled the terminal to the engine temperature sensor while it’s missing, PC says motor is at 75 degrees when I do this, nothing changes in the miss. And when I use the PC to shut off either injector, the motor still misses but oddly accelerates a 100-200 rpm.

 

[slomo]

I can remotely fire the injection pump using the computer, and both injectors fire fine.

What does the spray pattern look like?

The spray pattern is just a tiny squirt

Tells me the injector/s are dirty and or low fuel pressure. Should be a misting cone like pattern. A tiny squirt like a male child urinating is not good.

Take a 9v or 12v battery. Energize the injectors. Spray carb cleaner backwards if possible. Then flush forwards. Eye protection is a must doing this. See if your injectors have any type of fine mesh screen on the injector.

 

[slomo]

I’ve also pulled the terminal to the engine temperature sensor while it’s missing, PC says motor is at 75 degrees when I do this,

Either your scanner tool is not updating as in you are looking at live data or something. Pulling the wire off the temp sensor should tell the computer the block is say -40F or something crazy out of the norm.

This should be no different than a car engine. The temp sensor is like the conductor on the entire engine. Block temp tells the computer how much fuel to fire, timing to advance or not and so on. MAP sensors and the like assist the computer as well.

Should be able to short the wire/s to the temp sensor and watch the temp either rise or fall. Insert a resistor should show a change as well.

 

[slomo]

Did you get it running proper?

 

[Bmp4510]

No I haven’t worked on it. Been planting 210 Cacao Trees. Did take a compression check. One cylinder 92psi the other 64. 64 psi is the minimum per Kawasaki. All shrouding was removed to install new coils. And fins were cleaned, but not horrible dirty. Where the mower is at gets 200”+ of rain a year, so normal dust and debris are considerably less than the mainland.

And the scanner is correct on the temperature probe, it’s not like an automotive sensor. Guessing the motor gets warm, and the cylinder with the lower compression gets a valve guide hot and holds a valve partially open, or something like that. I don’t have a suitable dry and clean the location to tear the motor down. So we are looking for a shop that will do it. I appreciate your help.