John Deere 6430 tractor

[RogerHillier]

Jan. 1 ,2026
JD tractor with 5000 hours on it will not start when it's up to operating temperature. It will only start when it's cold. Otherwise runs perfect.
This model doesn't have access to codes and will require an analyzer from JD to determine the codes. Does anyone have an idea as to what sensor may be at fault ?

 

[Tx Jim]

During cold temp engine start does a cold start device such as air intake heater automatically engage? How long since fuel filter was changed? I suggest to check for good fuel flow from tank to inj pump. Is fuel tank venting?

 

[RogerHillier]

Thank you for responding. The engine only starts when it's cold. It will not start when up to operating temp. Yes the fuel filter was changed and the tank is vented. I agree. I think it is a fuel issue or lack of fuel being supplied. There are a number of sensors controlling the fuel. The question is, which one acts up only when hot.

 

[oldnslo]

I don’t know what sensors are on your 6430 but a question that comes to my mind is what or which sensor would allow the tractor to run when warm but stop fuel flow when hot?

Have you checked the fuel shut off solenoid? If for reason it gets weak when warm and doesn’t pull in would definitely prevent starting.

 

[RogerHillier]

I agree. That's the problem. I think there may be 3 involved. If I could only get the codes up , I think it would give me a good indication as to which one. I have a gut feeling I may have to bite the bullet and get a JD tech with an analyzer to solve the question.
Here in Northern Ontario Canada, a qualified tech are few and far between.

 

[oldnslo]

Are the three sensors in question accessible? If yes can you take a hair dryer or heat gun and carefully warm one up and then try to start the engine while cold? Might identify the problem and might just waste your time..

 

[RogerHillier]

Thank You and an excellent idea. Two are fairly accessible, the third not so much, but it may work. It is certainly worth a try. It may be a process of elimination.

 

[sixdogs]

I had a 5520 with a similar problem. I believe you have a similar engine.

There is a sensor on the engine left side that goes into the thermostat housing. It tells the timing to advance or ****** based on the temp of the coolant. When if failed for me it would not allow the tractor to start if cold.

Perhaps if it won't allow a start when cold I can see where it would not allow a start when it's hot. It's a $100 part. You can test this, I think, if you disconnect a wire to the sensor and see if it starts. Just a guess but a good one. I have found problems like this are usually simple. Start simple and work up, not the other way around.

 

[RogerHillier]

I had to employ a John Deere mechanic today because the tractor would not start. He used the scanner to determine that the high-pressure rail sensor was showing 2000 psi when it should have been 0 psi. He replaced it, as well as the solenoid for the shutoff. Apparently, those solenoids have been problematic, and the new ones are twice the size in coil length. With 5000+ hours on it, it‘s probably nearing the end of its life. When I tapped on it, it had a whining sound, which I believe was not a good sign. I just used it tonight to blow out the yard, and it worked fine. Thanks to everyone for their suggestions.

 

[beenthere]

Great to hear back and that you are up and running.