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New Holland 6640 injector pump problem?

D

davida

Member
I have a 6640 that wants to rev up when going down hill. If I have the throttle set a 1600 rpm and if I don't throttle it back down it will rev up to 2200-2300 rpm or so depending on the grade. Going uphill the governor works like it should and maintains engine speed.

Could this be a governor issue and needs pump work or anything outside the pump that could be adjusted to help with this?

My 4610 and 4020 do just fine on these same hills.
 


That sounds normal to me. Any diesel truck or tractor that I have ever driven will speed up going down grade, depending as you say on steepness and load. The governor can increase power when going up hill, and maintain speed within the ratio of power to load and steepness. When descending the engine has very little ability to hold RPMs down against the force of gravity. Many trucks that carry heavy loads are equipped with "exhaust brakes" that prevent the engine from producing any power at all instead of still producing slight power with the foot off the pedal.
 
There's a chance the injection pump governor is not shutting the fuel metering valve off as it should. That is checked/adjusted on the test bench during calibration. I've
seen this complaint happen before. Could also be the wrong size metering valve installed in the hydraulic head with an oversized valve bore, a standard valve in an
oversized bore WILL cause poor governor performance.
 
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