4520 Rev-Up At Cranking

gabby · Dec 9, 2004

My 4520 is programmed to rev up suddenly as soon as the engine cranks up, regardless of how low you have the throttle lever. It's annoying and downright scary because you think the engine is running away with you. JD says this is to blow the soot out and meet emission req's. I have two problems with it.

1. I don't think it's good for an engine to rev up immediately.

2. I run horse shows at my farm and I'm sure that some day it will get cranked up near a strange horse and spook the heck out of the horse and hurt somebody.

Does anybody know how to re-program the computer to not do it?
Gabby

BigAl · Dec 9, 2004

Gabby ,

"JD says this is to blow the soot out and meet emission req's."

That is the lamest excuse I have ever heard ! That goes against "every rule" I ever learned about warming up a diesel engine . I would be checking that statement with someone else at JD . That trick would have got me fired ,where I worked !!!
Big Al

RoyJackson · Dec 9, 2004

"...and meet emission req's"

That's probably the exact reason right there

However, it's highly unlikely you'll be able to reprogram the computer. No doubt you'd void any warranty if you even tried.

One thing you could do is go to your dealer...see if they all do this. If so, just hope Deere did it's homework for engine longevity. Another thing is to go to a Kubota or New Holland dealer to see if their tractors do the same thing. If so...not much you can do.

How long does it stay at high RPM? A few seconds?

The manual for my 790 says to set the throttle all way open for starting, then reduce the throttle once started.

I'm not sure if they're still available, but there used to be pre-oilers that would circulate the oil before one started the engine. This, of course, was to reduce start up wear and tear on an engine.

Cheyenne · Dec 9, 2004

The 20 series CUT Operator's Manual says to position the throttle at 1/3 fast for starting. This results in relatively high RPM at startup, and is designed that way to meet California emission requirements for diesel engine-equipped agricultural equipment. My 4520 also starts at high RPM, even with the throttle at idle position. Like you, I feel uncomfortable with that startup method, but if it keeps the EPA from banning diesel engines altogether, then I can live with it.

texastomtom · Dec 9, 2004

My 4720 does it also,,, as I'm sure all 20's do....

I agree,,, seems hard on the engine /forums/images/graemlins/frown.gif

tom

Dutch445 · Dec 10, 2004

Here is Deere's tech response to the startup of the new 20 series tractors. it just seem too high to me also...

( Solution Number: 65079

Solution Summary: The engine emits a puff of black smoke, runs the RPM's up to aprox. 1800 RPM's, and then settles back down to 950 +-50 RPM's.

Publication Date: Jul 27 2004

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**Paper copies of solutions may not be the most current solutions**

Complaint or Symptom:

When starting a 4120-4720 CUT, the engine emits a puff of black smoke, runs the RPM's up to aprox. 1800 RPM's, and then settles back down to 950 +-25 RPM's.

Problem or Situation:

During starting, the rack that controls the individual fuel injection pumps is held in the fuel delivery start notch (max fuel with timing advance) until the governor pulls it into the position needed to run at the speed commanded by the throttle. To ensure a good start, especially in cold weather, JDPS designed the rack magnet to hold the rack in the start notch until the govenor overcomes the magnet at approx 1800rpm. This RPM can vary by +/- 300 RPM.

Solution:

This is a normal engine start up procedure for the 4120-4720 Compact Utility Tractor.

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4520, 4720, 4320, 4120

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FUEL, GOVERNOR, ENGINES, ENGINE, Engine, 0406
)

BGL990 · Dec 10, 2004

It's not just the JD engines. My 990 (Yanmar engine) does the same thing when it's cold. It doesn't do it when it's warm but the first time I started it with the temps around freezing it sounded like it was going to throw a rod and I couldn't slow it down. I thought the throttle linkage was frozen up or something.

As an aside, it also seems to keep the intake air pre-heater going for a while as well. When it is cold out, the engine actually smokes less at first than when it is warm out. After a couple minutes, it seems that the engine decides it doesn't need the intake heater and fast idle any more and suddenly the rpm drops and a good bit of white smoke starts pouring out. There is a very distinct change in sound as well - from a normal-ish diesel knock to a smoother, quieter sound characteristic of this engine when it is cold. When the engine warms up "for real", the smoke tapers off, the diesel knock comes back, and everything is normal again.

Like everyone else here, I hope the sudden high rpm at start up doesn't impact the engine life too much! /forums/images/graemlins/confused.gif

DDT · Dec 10, 2004

That is too bad I have all ways like seeing a good puff at start up.

gabby · Dec 10, 2004

(
During starting, the rack that controls the individual fuel injection pumps is held in the fuel delivery start notch (max fuel with timing advance) until the governor pulls it into the position needed to run at the speed commanded by the throttle. To ensure a good start, especially in cold weather, JDPS designed the rack magnet to hold the rack in the start notch until the govenor overcomes the magnet at approx 1800rpm. This RPM can vary by +/- 300 RPM.
)

Thanks for the JD scoop, Dutch. Very interesting.

Where do these geniuses address the extra wear and tear on the engine due to this brilliant solution to crankup smoke?

I'm hurting my engine every time I crank it just to save a few nanograms of pollution. How can I disable this feature?
Gabby

RoyJackson · Dec 10, 2004

"I'm hurting my engine every time I crank it just to save a few nanograms of pollution. How can I disable this feature?"

I'm pretty sure you cannot disable this feature..but you could add a pre-oiler. I was going to link a site, but do a search...there's quite a bit of info on them as to the value of using them.
I'd probably add one, just for piece of mind...
A block heater might be of value too..or a sump heater might even be better. Atleast the oil would be warm enough for faster circulation.

If you could figure out a way to disable the starting feature, there's little doubt you would void any warranty.