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2120 won''t hold rpm

F

fairmountvewe

New User
Evening all.

I am the owner of a new to me 2120. I bought it as an open station utility tractor to mow some grass, run a post driver, that sort of thing. Today was my first day using it, and I cannot seem to make it keep a constant rpm. It will normally idle quite nicely once it is warm, but as soon as I put the bush hog on it and ran it at PTO speed, it would randomly vary from less that 1500 rpm to over 2700 with no rhyme or reason to the variance. No change to the throttle position, no change to the load, or terrain or anything that could account for this huge swing in rpm. I fought with the throttle lever pretty much all day to try and keep it somewhere near 2200 (PTO speed), so very frustrated. I think I may be looking at an injector pump rebuild? Is there anything I can do to narrow the problem down and provide a more competent description to the repair shop? Are the injector pumps rebuildable? Thanks for your time and help with this.

Peter
 
If it is a DB pump, you have issues with the governor coupler.
But a 2120 should have been built in Mannheim and should have a French built engine with a Rotodiesel pump, same as CAV. Those do not have this issue. I do not know the issue in this case, except maybe air getting in the pump, as the CAV is way more picky.
 

Ok. I guess air in the pump is within the realm of possibility. The injector pump does look like there is a new gasket at the top of the governor assembly, and there is a newer mechanical lift pump providing fuel to the injector pump, but the tractor starts easily, and idles well. Wouldn't air in an injector pump prevent that? I will head out to the shed and see if I can come up with some kind of identifier on the injector pump. Thanks for the information.

Peter
 

Start with the basics and ensure there is not 50 years worth of crud in the bottom of the fuel tank and in any of the fuel lines .
mvphoto57305.jpg
 
Good point, but the fuel is new, fuel filters (from Deere) are new, air cleaner is new. I think the input side of the equation is covered. Given the randomness of the variation, I think there is something amiss in the Injector pump. Perhaps a component not free to move, or binding, then releasing to a (now) false value (if that makes any sense). No, I am pretty sure I am looking at an injector pump issue.
 

I thought the fuel tank was clean in my 1640 until the boys ran it out of fuel. Then poured a jerry can of fuel into the empty tank with the stream of fuel bull's eye on the trash sump in the bottom of the tank.
Plugged the lines, plugged the low pressure pump and plugged the fuel filter.
Took a while getting all the dirt flushed and blown from the lines, low pressure pump and tank. I was appalled at how much filth was in the system.
Low rpm and hunting was one of the symptoms.
 
Bit of an update in case anyone else stumbles across this. I spoke to a local fuel injector shop here in town, and his recommendation was to run some fuel conditioner through it before I started tearing things apart. I emptied a bottle of Stanadyne diesel conditioner into the tank, and headed out with the bush-hog in tow. A couple of hours later, the improvements were noticeable and quite surprising. It will now stay at a pretty constant RPM, and doesn't seem to be hunting at all. I am more than willing to call this solved, so here's hoping. Thanks again to everyone for all the advise and help. Take care.

Peter
 
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