John Deere 4020 surges

[45-100]

My apologies if this has been covered before. I have an early model 4020 with a Stanadyne DBO-1578 injection pump. Several years ago I had the pump rebuilt by a commercial rebuilder. I have less than 100 hours on the rebuilt pump and the engine starts speeding up on its own, without moving the throttle. Everything I have read suggests the governor ring in the pump is bad but I would think it should have been replaced and possibly updated. Is there something else that would cause this to happen?

 

[thepumpguysc]

If it’s speeding up on its own and the throttle has no effect on the rpm’s..
Don’t start the engine until it’s diagnosed and fixed..
It’s possible that the flex ring has deteriorated OR it was put on improperly..??
There WILL come a time when you won’t be able to shut it down..
I’d love to have a crack at it…
Seeing your new, u probably don’t have enough “credits” to contact members thru the prvt msg yet..
So u can contact me directly by using my screen name at aol dot com in your mail service..
I’ll treatcha right..

 

[45-100]

Thank you for that reply. What you say makes sense.

 

[Tyler d4c]

Thank you for that reply. What you say makes sense.

He's our resident pump expert he's done work for me with good results. You'll be happy

 

[Delmer]

Make sure it's not sucking air somewhere. Check any rubber fuel lines on the suction side for cracks.

 

[45-100]

I have been concentrating on the return lines. Hadn’t thought about the intake side. Thank you Delmer.

 

[crbearden]

If it’s speeding up on its own and the throttle has no effect on the rpm’s..
Don’t start the engine until it’s diagnosed and fixed..
It’s possible that the flex ring has deteriorated OR it was put on improperly..??
There WILL come a time when you won’t be able to shut it down..
I’d love to have a crack at it…
Seeing your new, u probably don’t have enough “credits” to contact members thru the prvt msg yet..
So u can contact me directly by using my screen name at aol dot com in your mail service..
I’ll treatcha right..

I hate to jump in here on an old thread. I have rebuilt a few of these pumps, or I should say I resealed them with a seal kit. I have installed the governor ring for the stationary engines in the ones I have rebuilt. It doesn't have the rubber to deteriorate and I have found that tractors are not used in a varying speed application like a automotive pump would be. I think this later diesel and the additives we have to use tears up a lot of rubber lines and internal parts. Just my $0.02