How to start diagnosing crank-no-start on a kubota common rail diesel

[PoTreeBoy]

This is very weird indeed. The battery is pretty new and shows 12.8V. My charger is 30amp and runs at ~14 volts. The battery has no trouble running the starter alone. However, it will only start if I have the charger on and it starts right up, on the first crank. I am thinking that the slightly higher voltage 14 vs. 12.8 is the key

This is coming from left field, but are you maybe wiggling a power wire from the battery clamp when you connect the charger clips? Have you tried starting it with the charger connected but turned off/unplugged?

You wouldn't happen to have a schematic? Since this is a stationary installation, it might be significantly different from a tractor.

 

[whitetiger]

focus on whatever STOPS the engine from running when you turn key to 'off'.

The ECU removes the ground from the injectors.

 

[hodge]

I've checked it last night. It gives great cranking current - over 300 rmp. I think there is no easy solution here, I will need to read the manual and start diagnosing step by step

I know that on automobiles, if the voltage drops below 11.2 or something like that while starting, it will affect the electronics.

 

[lugbolt]

you need to be able to see the fuel rail pressure to eliminate that part of the equation. IOW, on the tractors, if you are hooked up to diagmaster and can log rail pressure while in a crank/no start condition, a lot of times you can see rail pressure rise and drop for each injector's opening. If an injector is stuck closed, you'll see a normal rise and fall for the rest of the injectors and a big spike and no or little fall for the one that is not opening. Or if one is bypassing too much, no or not enough rise. Also need to see SCV voltage among other things to know if it's doing it's job.

Sadly without being able to see that stuff, it's just gambling and possibly throwing parts at it. And firing the parts canon gets real expensive real quick.

 

[InTheWoods]

I checked my charger and it is rated for up to 50 amp. So I am pretty sure that the voltage remains stable.

No. If your starter is pulling 300A, as you say, your battery voltage is NOT 'remaining stable'.