# 07 JD 4720 surges under load



## Leche0080 (Oct 7, 2020)

Good morning,

I am not much of a diesel mechanic, but quite knowledgeable on any combustion engine, so there’s my disclaimer.

My 2007 4720 starts and idles quite well. Very steady rpms. Sounds great. But as soon as I put any load on it, be it engine load or hydraulic load from the backhoe, the rpms oscillate up and down about 100 rpms very consistently. The only relief is removal of throttle/load.

It has fairly low hours though I have not checked them and I’m not next to it at the moment. It does not leak, and does not have any smoke coming out. I took it in to the local shop and after $2,000 in work, they returned it with the same issue and recommended a new engine, which I cannot believe is necessary. Among other things, on the repairs list was a new air and fuel filter. Everything I’ve read says not enough air or fuel. 

Any suggestions as to what I can try next?

Thanks!
Ryan


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## Tx Jim (Jul 28, 2020)

Welcome to The tractor forum. 
How long since fuel filter was changed? Have you checked for good flow from tank to inj pump. Is fuel tank venting IE not creating a vacuum when fuel is exiting tank. Have you checked condition of air cleaner element.


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## HarveyW (Sep 15, 2014)

Like TxJim says, you must have a good flow of fuel from the tank to the injection pump. A trickle flow is not good enough. 

Most tractors have fuel screens in the system. Look for partially plugged screens: 1) Cylindrical-shaped screen attached to the fuel tank shut-off valve, sits up inside the tank. 2) If your tractor has a lift pump, there might be a screen on the inlet side. 3) If your tractor has a sediment bowl, look for a screen in the top of it.


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