Kubota B7800 - hard starting, lots of smoke, low idle

[Sniggle]

Hello all, I need some help diagnosing this problem. Started a couple of months ago, but seems to be getting worse. When I go to start her, she smokes black smoke and has a very low idle. As she warms up, after about 10 minutes, she seems to operate normally and have expected power.

Checked oil, diesel, air filter...no problems. Changed the fuel filter when this all started, although the old one looked good.

My thoughts are:
- Issue with the glow plugs
- Issue with the fuel pump

I did have a mouse in the dash last winter, and all my idiot lights except the glow plug indicator and tach are out. Not sure, but could be related issues.

Any help/direction would be appreciated.

 

[seville009]

I wouldn’t think it would be the glow plugs or pump, but I’m no mechanic.

Your description sounds like what happens to me when it’s below zero out and the fluids are thick from the cold. Runs rough until I’ve let it warm up for awhile.

Is your oil and oil filter relatively new?

Probably not related to the mouse either, since a chewed electrical line would either work or not (vs getting better as the engine warms up).

 

[Jerry/MT]

Hello all, I need some help diagnosing this problem. Started a couple of months ago, but seems to be getting worse. When I go to start her, she smokes black smoke and has a very low idle. As she warms up, after about 10 minutes, she seems to operate normally and have expected power.

Checked oil, diesel, air filter...no problems. Changed the fuel filter when this all started, although the old one looked good.

My thoughts are:
- Issue with the glow plugs
- Issue with the fuel pump

I did have a mouse in the dash last winter, and all my idiot lights except the glow plug indicator and tach are out. Not sure, but could be related issues.

Any help/direction would be appreciated.

Black smoke is either too much fuel and not enough air but this clears up after a few minutes. You checked the air filter, and you say that's OK and the fact that it clears up after a while and you have a new fuel filter tends to say that the fuel delivery is good.
I would suspect the glow plugs. Make sure there is power to that circuit and they are all operating.

 

[Ed ke6bnl]

I also have the b7800 just a guess but a leakt fuel injector loading the cylinder.

 

[Sniggle]

I went out to start it again after about 6 hours. It started fine, with just a little puff of black smoke at ignition. I will try starting it again tomorrow morning after sitting for about 14 hours and see what happens.

I am starting to think that one of the fuel injector is bleeding down into a cylinder, so after it sits for a while that piston has a puddle of diesel fuel sitting on top of it.

After my test start tomorrow I will also call my dealer and get their take on it.

 

[Ed ke6bnl]

my old ford 3500 must have had a leaky injector, I found the oil level to be way above normal. on that old junker I changed the oil and then made sure to shut fuel supply from the tank. BUT that led to several times starting without fuel and having to reprime the tractor ( a real pain). Just a thought

 

[orezok]

My 7800 always has a puff of black smoke on starting as the pump goes full rich until it starts.

 

[Sniggle]

Update: Started it this morning and it started right up with no black smoke and ran well, up and down the RPM range. I plan to get a bottle of diesel Kleen and dump it in the next full tank.

I will start it again on Saturday, and see what it does.

 

[orezok]

If you have not noticed ANY black smoke when working the tractor hard, you may be a little under fueled and giving up some horsepower. At the front of the injector pump is a cap with a security wire. Cut the wire and remove the cap. Adjust the screw 1/2 turn clockwise and work the machine hard. If no smoke then go another 1/2 turn. If you get significant smoke, back off until you get just a smidgen of smoke. Put the cap back on.

My 7800 is 7 turn clockwise from counterclockwise stop but I am located at 3500MSL. Yours may be different.

Mine has been running at 7 turns for at least 10 years with no issue.

 

[Sawyer Rob]

My guess is a glow plug issue!

SR