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Discussion Starter · #1 ·
Have a JD Z930M with a Kohler ECV749 747. The repair person says it needs an O2 sensor. The part he claims is normally $300 but he found one for $150. I have never heard of an O2 sensor costing $300.

The engine will not start or run. I was able to get it to start with starter fluid but it only runs for a moment. I assumed a fuel pump, he said no it was the O2 sensor.

Any help is greatly appreciated on whether he is giving me a story.
 

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If you Google parts places for that engine, the O2 sensor goes for between $125 and $150. I don't have that engine, but in others a bad O2 sensor won't keep an engine from starting. But, it could make it run rough.
 

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It might depend on what exactly the problem with the O2 sensor is, and how the code in the EFI system is written. It might not let the engine start if the sensor isn't reporting a resistance within a certain range (ie, if the sensor reads as if it's not connected).

But I don't know the specifics of your engine.

It may or may not be the problem, it really depends on what diagnostics the tech has done, if they have the setup for connecting to the efi computer to see what it thinks the problem is, what tests they did on the O2 sensor and wiring...
 

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Discussion Starter · #6 ·
Ok, sooo, the end of the story is as I suspected. He put the O2 sensor on and that didn't change anything. It still doesn't start and it still puffs smoke. So he said he can't fix it and I needed to pay him for the sensor and take the tractor somewhere else. GREAT! I love mechanics who have no idea and start replacing parts. He claims it did show the code for the O2 sensor but that's like fixing a flat tire and saying well it didn't fix the main problem but the tire was flat.

Onward and upward we go.
Thanks
 

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Don't forget to get the old O2 sensor as it may not have been bad at all; no sense letting him put it in his "parts bin"!
 

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Discussion Starter · #9 ·
So we finally found the issue with the mower. Someone put diesel fuel in the gas tank. Now I never even thought to check that as none of us who use the mower would ever mix diesel with gas. We do have some diesel around but it is in the yellow can as it should be. I have asked everyone here and they all agree that they knew the diesel was in the yellow can and know not to put it in the mower. Crazy. I hate to think someone sabotaged this thing but don't know what else to think. Anyway thanks for all your help.
 

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Wow who would expect that. Trying to burn diesel fuel probably fouled the O2 sensor. That is probably why it tested bad.
 
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