# will not rev over 1500 rpm



## usmcncoic

I have a case 385 international tractor. I cant get the engine to rev over 1500 rpm load or no load and rpms drop when under load like there is something bogging down the engine. Any ideas on how to remedy this?


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## sixbales

Howdy usmcncoic,

You may have a fuel delivery problem, or possibly an obstruction in your air intake system.

Have you changed the fuel filter recently? 

Is the lift pump pumping ok?

Do you have good flow from the fuel tank? Could be debris in the fuel tank. Maybe a plugged screen (Fords have a screen that sticks up inside the tank)? Check fuel flow from the tank all the way to the injection pump.

Have you cracked open the injector connections (with engine running) to purge any possible air out of the system? 

Check the air intake system for a rats nest, birds nest, etc.


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## sixbales

I did not address the possibility of governor failure. Below is a post by *RodInNS* on the YT forum. Rod has a lot of experience and is a very reliable source of information:

"The first thing I would do is check the stops on the pump. If it looks like a duck and talks like a duck...
So... with the tractor running at idle, slowly increase the speed with the throttle while watching the linkage on the pump. When it reaches the point where it no longer responds to throttle lever movement, look at the linkage on the top of the pump and see if it's bottomed against the high idle screw. If it's not, move the linkage at the pump with your finger and see what happens... I would say if it isn't bottomed out on the stop and won't respond to throttle... you have governor problems. If it does respond... you have a tractor related linkage problem. That kind of stuff happens on 50 yr old tractors...
Rod "


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## usmcncoic

I recently have changed the fuel filters. I have checked the air intake system and have no obstructions. The throttle lever does bottom out on the pump. Also I get blue smoke from exhaust, while warming up and when I take load off of engine while using the tractor. I cannot get it over 1500 rpm with or without a load on the engine. I have a gravity fed fuel system so there is no pick up screen in the tank.


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## sixbales

Another thing to check is for a plugged fuel return line (low pressure line) from the injectors back to the fuel tank or suction system. A plugged line will cause problems such as you re experiencing.


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## usmcncoic

OK I will try to blow out the return lines and see if that works. Also would that cause a lose of power and and lose of engine rpm while under load or cause blue smoke from exhaust?


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## sixbales

A plugged return line will cause a diesel to lose power and RPM. Don't know about blue smoke. 

My neighbor's Kubota diesel used to periodically get into a funk and lose power & RPM. I would crack open each injector while it was running and cure the problem for a few months. Then he would be back again. I'm sure he was getting air into the injection system in some manner, but I never located the source.

I think your next step will have to be getting the injectors serviced?? Check the return line first. Bad injectors will cause a diesel to lose power & rpm.


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## usmcncoic

OK, I did not have the injectors serviced but I think it wouldn't hurt either to have it done. also I will check the return line.


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