# 7740 engine surges/lacks power



## JDownard (Jul 15, 2016)

I've got a '98 New Holland (I think, not positive on year) that has around 4500 hrs, I've changed the fuel filter, but the tractor will surge (increase/decrease) rpm without changing throttle position periodically. The tractor is also lacking in HP. I mostly pull a 10' bush hog, and when I start up a hill, I have to shift down 3-4 gears to maintain rpm. I believe this tractor has an electric lift pump, but I've not checked fuel pressure yet. I've searched the internet, but can't find any kind of consistent issue with the engine that I'm encountering. I've ordered a service/troubleshooting manual which should be here within a week. Does anyone have any thoughts.

First time posting here by the way.


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## sixbales (May 18, 2011)

Howdy JDownard,

Welcome to the tractor forum. 

You may have a very small air leak somewhere in your fuel system. Filter seals are a likely source. Spin on filters sometimes leak at the seal where they seat. CAV filters can leak at the flat o-rings, especially if they've not been changed with the filter, or not installed properly. 

See attached parts diagram. Separator assy (item #40). Filter (item #41).


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## sixbales (May 18, 2011)

My ex-neighbor's tractor would lose power periodically, and he would bring it over. With the engine running, I would take a wrench and crack open injector connections, at the injector, one at a time, to bleed any air trapped in the connection. Then tighten and go to the next injector. Worked on that tractor every time. Might work on yours. 

Finding the source of the air leak is another thing. Your injection pump may be pulling a slight vacuum due to an obstruction in the fuel lines/system. 

Give this a try. Only takes a few minutes.


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## JDownard (Jul 15, 2016)

Thanks guys. The tractor does have an electric fuel pump situated above the rocker cover. I'll try cracking the injector lines, but don't have high hopes of that being the issue. The tractor purrs like a kitten and runs flawlessly. It's just that it will surge in rpm every once in a while when at low load, but when transitioning from flat ground while mowing over to a hill, it will fall on it's face. It never stalls out, but it will pull down to about 1000 rpm. Fuel starvation seems the most likely cause. Instead of getting air into the system, the fuel seems to be restricted getting to the injector pump thus causing the motor to drag down.


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