Engine stuck on high RPMs- 2005 JD 4720 Diesel

[EdAvilaSr]

The RPMs suddenly went to the max and the speed lever would not slow it down no matter what I did. Could only shut it off by clamping the fuel hose

The tractor would not go off by turning the start key and the tractor would not go forward or in reverse

I was told it is most likely a frozen/stuck fuel injection pump.

Any other ideas of what could cause that?


thanks

 

[Spanner]

yes. It happened to a 4720 we had in the shop once. Originally the engine wouldn't maintain goverened revs. The workshop stripped it and found nothing then after reassembly the same max-revs occurred. A runaway condition which can prove catastrophic. I happened to be collecting parts for field-work and ran, like others, to assist the tech. Leatherman pliers used to clamp the fuel hose and someone grabbed a screwdriver and punctured the fuel filter - It was chaos!
Eventually the fault was found to be a loose-fitting lever on the throttle or governor arm behind the cover plate on the timing cover.
I can't recall exactly which it was (Throttle or governor) as I left the workshop to clear it up and ventilate the smoke!!
It was one of the un-numbered items like on the shaft assemblies shown in this pic:

Item #27 or #38 I think. It's a 'press fit' and had come loose so it could rotate, occasionally 'sticking' and making goverened idle speed setting intermittently impossible.
The pic may not be of your engine. It is from the 4024TLV08-RE530181 Parts List here: John Deere Parts Catalog

Hope that helps.

 

[EdAvilaSr]

Wow, that could have ended in disaster for the engine :shocked:. I hope it doesn't happen to mine when the shop takes it in and tries to fix it

I will let them know about your experience so they check for loose fitting parts on the governor and throttle

Thank you very much for sharing! :thumbsup:

 

[Spanner]

If you're going to a JD Dealership ask them to search DTAC for you (Dealer Tech Assist..) and they should find some reference to the upgraded parts. From lunch-room chat I believe it wasn't an easy 'find' as the parts looked and felt ok. Engine was stripped and ran twice before they found it. Glad it wasn't on my time-card.

A run-away diesel is a frightening spectacle!

 

[Rara Avis]

If you're going to a JD Dealership ask them to search DTAC for you (Dealer Tech Assist..) and they should find some reference to the upgraded parts. From lunch-room chat I believe it wasn't an easy 'find' as the parts looked and felt ok. Engine was stripped and ran twice before they found it. Glad it wasn't on my time-card.

A run-away diesel is a frightening spectacle!

One can stop a Diesel engine runaway by directing a CO2 fire extinguisher into the air intake to smother the engine...

 

[Spanner]

Correct. If you have one handy...

 

[Rara Avis]

Correct. If you have one handy...

I have one in my shop after i saw it demonstrated on a fire call...

 

[Deere Dude]

I have one in my shop after i saw it demonstrated on a fire call...

I'll have to get one to strap to the tractor. Good idea.

 

[EdAvilaSr]

Will it be easy to start it again after using the extinguisher?

 

[finn1]

CO2, not dry chemical.

You don't want to try to restart the engine until the injection pump is repaired.

A runaway usually won't hurt an na engine because the volumetric efficiency nose dives at high speeds and friction overcomes airflow limited power.

A turbo engine is another story.