Injector pump question

[crazyal]

My neighbor has an old Yanmar tractor he got for real cheap but was half torn apart for a transmission issue. A few weeks ago he got it back together and was disappointed with it's performance. It just didn't have any grunt. He finally had a diesel mechanic friend look at it and he discovered that the governor inside the pump wasn't working correctly. When the engine would bog down the governor wasn't opening up enough to allow the full amount of fuel the engine could burn to the injectors. Now when he really works it you can see a little black smoke come out the exhaust where as before it wouldn't.

I can't say I've ever seen anything from the exhaust that would indicate I was working the engine hard. I assumed that the EPA clamped down and mfgs had to cut down on the max amount of fuel they could put into a given displacement. So how would one know that the governor is allowing the engine to make full power (without going to a dyno)? Does Kubota have a test? I assume that the pump would need to be removed so it could be disassembled.

Anyway, I was just curious. I remember post in the past about people complaining about not enough power.

 

[Chilly807]

The only sure way is to put the pump on a test bed and check the output. The dealer would have to send the pump away to have that done, it requires specialized equipment 99% of dealers won't have. A chassis dyno will tell you too, but they aren't common either. Never seen one for a tractor.
When the pump is adjusted initially, they are limited to a specific output per stroke, usually averaged over 1000 strokes. For instance, it may be 50 cc per 1000 strokes, which gives you a measurable amount of fuel rather than saying .05 cc per stroke.
Black smoke is indicative of excess fuel or too much load. Ie, the engine can't burn all the fuel it's getting. Also an indication of late injection timing, since the fuel goes into the cylinder too late in the cycle to burn completely. Either is possible, timing is easier to check. An exhaust temp measurement may help tell you if the timing is late if you have a normal baseline to refer to. Late injection means the fuel is still burning as it goes into the exhaust stream, which drives up exhaust temps.
Fuel delivery volume, if the timing is right, will simply make more or less horsepower within the engine capability. If he's not getting enough fuel, black smoke is unlikely. Is the engine turbocharged? If so, I'd suspect turbo problems or an issue with the fuel pump limiter, since almost all modern turbo engines have a device to limit the amount of fuel injected until there's enough boost pressure to burn it properly. Again, unlikely to get black smoke in this situation.

Simply "turning up" the fuel delivery may make more power in some cases. However, that particular engine may require other changes to enable it to effectively use the extra fuel. The L series Kubotas are a good example of this. Same basic engine in the L3400 and L3800, yet one makes more power. Is that solely a fuel increase, or are there other changes? I don't know, it's dangerous territory fiddling with fuel settings without being able to see the big picture.

Timing.

Sean

 

[KennyV]

Tractor dyno hooks up to the PTO...

 

[doxford jim]

To ask the obvious - did the air filter get checked for cleanliness ? Insufficient fuel will cause lack of power and black exhaust smoke. Just a thought.

 

[doxford jim]

Oooops - I meant insufficient air supply will cause lack of power and black smoke.
Sorry about the typo.

 

[Chilly807]

Jim's right, any restriction in the intake is poison to a diesel. If it sat for a while, mouse nests in the air cleaner are a real possibility.

Sean