JD920 won't start when engine is hot

[farmofthelake]

Our JD920 has about 580 hours on it after a complete engine rebuild by John Deere (previous owner paid for that). Tractor starts well and runs well, even in winter. Batteries are both new. This weekend was the first time we did some heavier work in the summer time, and ran the tractor for about 1.5-2 hours. I stopped for a 15 minutes break, and when I tried to start it after, it would not start. After about another hour, I tried again, it would not start. After about 3 hours, I tried again, and it started instantly. Today, the same thing happened.

When I say it won't start, it turns over easily, fuel shutoff is properly on, engine just doesn't start. Sounds like it never combusts (is that the proper term?) After the 3 or so hour break, when I try to start it, it starts instantly.

My uncle, retired farmer, suggested maybe a vapour lock in the line somewhere? A friend over the hill who owns a JD920 suggested either loosen the fuel cap or make sure fuel shutoff is properly open. The fuel cap has no gasket on it, something I still need to fix, so I don't figure there is a vacuum.

There is a chance that some water might be in the fuel, I have drained both filters and only a few drops of muddy fuel came out then clean.

Any other suggestions on what might be wrong, before I dig into testing more thoroughly?

 

[Tx Jim]

If inj pump head is worn the IP doesn't pump fuel as well when it's hot. I've read where people have poured cool water on inj pump then attempt starting.
I suggest to pressure test & check spray pattern of injectors.

Have you rotated steering wheel rapidly side to side or utilize a hyd pump destroking screw while engaging starter?

I suggest relocate battery ground cables from attaching to sheet metal to attaching to engine block.

 

[farmofthelake]

Thank you Tx Jim! A couple of questions:
1. putting cool water on a hot IP won't hurt it?
2. The steering/hyd pump comment, what does that do?
3. This I had wondered about when I changed the battery. Thought the ground cable to the sheet metal a little odd, when my other vehicles ground to the block or frame.

 

[Jim.ME]

Dieseltech may give a different answer, but cold water on a hot IP can seize some of them, I've seen the results of a cold-water wash on a hot Roosamaster pump, it seized. Use caution if you do this.

 

[farmofthelake]

Thanks Jim.me. Logic suggests this might happen, or worse, warp or crack depending on how hot.

I did notice, while looking through receipts from the previous owner, they had bought an IP gasket, which I was given with the tractor. Perhaps the owner knew of this issue, planned to fix but didn't? No idea of a bad gasket could cause this or not though. In case TxJim's comment about hydraulics has baring on the issue, my power steering does leak a lot at the base of the column. On my to-do list, once we finish the new workshop.

 

[Tx Jim]

I agree pour cool water on your IP at your own risk.

Moving steering wheel side to side while engaging starter helps relieve hyd pressure therefore causing engine crankshaft to be easier to rotate.

 

[farmofthelake]

I stopped at a JD shop this past weekend and spoke with a mechanic. He agreed, as long as I can put my hand on the IP, it is safe to pour cold water on it. Hotter than that, don't do it.

 

[buickanddeere]

Jimmy rig a 12V electric primary fuel pump on instead of the factory mechanical pump ?

 

[wore out]

Dieseltech may give a different answer, but cold water on a hot IP can seize some of them, I've seen the results of a cold-water wash on a hot Roosamaster pump, it seized. Use caution if you do this.

Pour as much cold water on the I.P. as you'd like, then wait a few minutes before cranking/trying to start for temperatures to equalize.

You can then try to start it with NO risk.