B7800 engine injector setting

[orezok]

First, I guess the drought must be over. :laughing: :laughing: We had rain yesterday, a whole 0.3 inch, the first in about 6 months.

Anyway, since the ground had a little moisture, I decided to widen out my property line fire breaks. They were about 25' wide but I wanted more. It is fire season out here.

I hooked up the tiller as I don't have a bush hog. It does a good job as it buries the light thin totally dried out brush and I don't have to haul it away. After about an hour of tilling at PTO speed, the engine started putting out light black smoke.

I checked and found that the injector pump "fuel limit" stud had backed out. I think because the jamb nut was loose. Not knowing which way to go, I turned the screw all the way in while counting turns. I started it and it would not go beyond an idle. This told me that further out enrichens the fuel. After a little playing around, It seems to run about right at 7 full turns out, but I don't know if this is correct.

Does anyone know how to properly adjust the fuel limit screw?

 

[orezok]

Common guys, is this "Stump the Stars"? Somebody must have an idea.

 

[rswyan]

I'm going up to the shed in a few minutes and I'll take a look in the Kubota WSM and see if there is anything in there that I can decipher on it ...

 

[orezok]

Thanks.

 

[rswyan]

Sorry for the delay ... I fell asleep on the couch and didn't make it up to the shed last night ...

No good news I'm afraid.

The WSM has sections for each area of the tractor (engine, brakes, hydraulics, etc.), and then each section is further subdivided into two categories: the first which just describes the area covered, and the second which covers any servicing procedures. The section covering servicing the fuel system is all of 3 pages long. Unfortunately, the WSM does not have an index.

The WSM does mention - in the descriptive section - that the injection pump used is a "Bosch MD mini pump".

The Workshop Manual does not really address the setting the fuel limit stud ... a number of things are addressed in the section on the fuel system (testing and adjusting the injection timing, checking the pressure of the pump element and delivery valve, injector disassembly, etc.) but that does not appear to be one of them.

The fuel limit stud is shown as a numbered item in one illustration (in the descriptive section) pertaining to the governor ... but it isn't even mentioned in the accompanying text, which is a description of how the governor operates.

I dunno, but I'm guessing that since it is not addressed, it may be that it is a "factory setting" type of deal (done when the pump is manufactured) and intended to only be adjusted on a test bench by a Bosch authorized service center, who has the appropriate equipment to set it correctly.

Someone (Brian, whose screen name I can't recall at the moment, but whose avatar shows his ink) who is actually a wrench may know otherwise.

Sorry I couldn't be of more help.

 

[orezok]

Thanks for taking the time to investigate.

Through experimentation I have discovered that the further out the stud is turned, the richer the engine runs. Generally, diesels produce more power as mixture is increased. I adjusted it so that when I am at PTO speed and using maximum power at the verge of bogging, as with my tiller, that just a barely visible amount of smoke is produced. Since I am at 3,500 MSL, this would still be leaner than at sea level.

It turned out to be about 7 1/2 turns out.

Thanks again.

Thanks again.

 

[brain55]

Thanks for taking the time to investigate.

Through experimentation I have discovered that the further out the stud is turned, the richer the engine runs. Generally, diesels produce more power as mixture is increased. I adjusted it so that when I am at PTO speed and using maximum power at the verge of bogging, as with my tiller, that just a barely visible amount of smoke is produced. Since I am at 3,500 MSL, this would still be leaner than at sea level.

It turned out to be about 7 1/2 turns out.

Thanks again.

Thanks again.

I have nothing to add you adjusted it just as I would have.

Brian

 

[rswyan]

I have nothing to add you adjusted it just as I would have.

Brian

Brian,

Do you know whether it is intended to be adjusted in the field ... as opposed to a diesel shop that is qualified and fully set up to do fuel injection work ?

(The local diesel machine shop I deal with is an authorized Bosch facility and they have a clean room with the test equipment specifically for working on and rebuilding fuel injection equipment)

 

[brain55]

It's not exactly intended to be done in the field, but not much choice in this case. It isn't a clean room job either, like the disassembly and repair of the injection pump internals would be. Best case would be using a dyno to set it exactly, but how you did it will work fine.

Brian

 

[orezok]

Brian,

Do you know whether it is intended to be adjusted in the field ... as opposed to a diesel shop that is qualified and fully set up to do fuel injection work ?

(The local diesel machine shop I deal with is an authorized Bosch facility and they have a clean room with the test equipment specifically for working on and rebuilding fuel injection equipment)

Yes, I found a site that has the full regime for setting up the injector pump. It takes a test stand with specialized equipment that measures the exact output of the pump. ...but the adjustor screw is on the outside of the pump so dirt doesn't matter and it is working just fine with "Farmer Tight" adjustment.

Would I attempt to rebuild the pump, heck no! This is just a simple adjustment for the max flow on the governor.