Need full throttle to start Kubota diesel

Stickerman69 · May 28, 2014

I have a 2004 Steiner 430 Max with a 21hp Kubota diesel that needs to be in full throttle to start? Replaced filters and glow plugs. Once started it seems to run fine from idle to wide open. Did notice if under heavy load it will blow black smoke out exhaust. Any ideas what is wrong? This is my first diesel and don't know much about them.
Thanls

Baby Grand · May 29, 2014

Welcome to TBN!
Both our B5100 & G5200 Kubotas (early & late 1980's production) start that way, so I'd say that it's normal.
Black smoke under heavy load is common, too. Whether or not the amount of smoke you're seeing is normal, I can't say.
Maybe some of the Steiner posse can give you a more informed answer, based on that engine/tractor combination.

Stickerman69 · May 29, 2014

Ok thanks

the old grind · May 29, 2014

:welcome: Are you sure the glow plug relay is ok, and have you verified its connection path to whatever activates it? (switch, timer, etc)

Texasmark · May 29, 2014

Black smoke on a new(ish) tractor signals unburned fuel and a lot of times that's due to excessive loading on the engine.....drop a gear. Course on older tractors where someone has diddled with the pump it could be too much fuel for the existing combustion system......trying to up the available HP. If you are trying to start a cold engine without glowplug assistance, you may get white smoke at startup. That would be a clue. Course white smoke is water/condensation and could be caused by running low rpms in cold weather.

My 2c,
Mark

Stickerman69 · May 29, 2014

Did not check the relay yet. The glow plug light goes on when turning switch to left so just figured it was working. Will track down relay and check. Is there a way to check at the glow plugs to see if they are working?

the old grind · May 29, 2014

Stickerman69 said:
Did not check the relay yet. The glow plug light goes on when turning switch to left so just figured it was working. Will track down relay and check. Is there a way to check at the glow plugs to see if they are working?

If the GP light is driven directly by the switch it could disguise a faulty relay. You should see ~12v at a GP connector when the light is on. Because of the GPs electrical resistance it shouldn't have to be unplugged to do this test, but it wouldn't hurt. One GP not working isn't always obvious, but if none do it's usually something else. Could also be 'nature of the beast', but I hope not.