John Deere 855/856 hard starting

[Hillwalker]

Hope all is well! I have a 1987 JD 855/856 compact utility tractor that has recently begun to be very hard to start first time in the day. It has 923 hours on it and a known history back to 2001-ish and has always been maintained well.

The tractor was used all summer for some general property upkeep and then I elected to do a full service on it in September of this year where the hydraulic, oil, coolant, and all filters (including fuel) were changed with all JD parts and JD fluids.

Current behavior is that first time in the day it will take nearly 4 attempts to start and it will blow a lot of black smoke while it is cranking. Once it has been started, it will stop and restart at will, unless around ~2 hours elapsed. Current weather is 58 degrees and it just exhibited this behavior again after resting for a few hours.

My suspicions as to root cause are either fuel-related or heat-related (32 degree nights versus 80 degree nights over the summer).

Here is what I've tried so far:
1. Using the tech manual, I have bled the fuel system at both the bowl and pump and did not see any bubbles. Have not yet progressed to the injectors.
2. Bought a test light and confirmed power at the preheater grid (this unit does NOT have glow plugs) when the light is on the dash, so I assume the heater is working.
3. Confirmed that the fuel stop solenoid activates upon start up and releases upon key turn off.

This tractor has had a history of effortless starts up until now and I'm hopeful I can restore that. Thank you in advance for any and all tips.

 

[beenthere]

Welcome to TBN
Help from the knowledgeable members will be along in due time.
Sure sounds fuel related, but I'm a novice to help further. A decayed fuel line or some stray dirt would be my suspicion. Hope you get it back to the normal quick starts.
Which Yanmar model engine?

 

[Roadworthy]

Check the air cleaner and path from there to the intake manifold. An inadequate volume of air will cause black smoke due to incomplete combustion.

 

[MTGreen]

When if ever have the valves been adjusted?

 

[D&D]

Load test the battery, slow cranking speed can cause Headaches too.

 

[Harry in Ky]

Next time you go out there try the air heater again, only this time put your hand on it. Hopefully you can reach it and the key at the same time. With power applied you should feel the area around the heater start to get warm after twenty seconds or so. You know the circuits work but you don't know (yet) if the element itself works.

 

[Hillwalker]

Answering Q's in-line below:

1. Engine model: Yanmar 3TN75RJ 1.0L diesel
2. Battery: I forgot to mention I replaced the battery first with a new one as I thought that was the problem
3. Valves: Unclear when they were last adjusted
4. Air cleaner path: Will check and report back.
5. Air heater temperature: Will check and report back.

 

[Hillwalker]

Reporting back that the air heater works and air clearer path seems clear.

 

[Harry in Ky]

I think you've pretty well covered the basics. I do question the part about black smoke while cranking. I must assume it never did that when it was starting better? Typically when attempting to start diesel engines the smoke is grey while cranking. What is your memory on that from past usage?

 

[Hillwalker]

Well, I just tried it again and it took 4 tries to start it and lots of black smoke. But once it had been running, I could turn it off and on at will no problem and the smoke seemed normal. If I wait a few hours, it probably will be hard to start again with the black smoke.

Does this sound like fuel de-priming to you? Again, I changed the fuel filter....so is it cranking a lot to pull fuel back into the system? I just bled it at the fuel bowl and pump again but still have not tried bleeding at the injectors as the instructions seem a bit unclear to me.