Bobcat 731 black smoke

[Madmack]

I recently repowered my 731 with a kubota v2003t. The problem I'm having is starting it when the engine is cold, it pours black smoke for about 60 seconds. Once it starts to warm up, the smoke clears right up. Is this normal? Also one of the injectors has a small leak. I tried tightening the line but I'm afraid if I crank on it anymore it will strip the threads. I dont have a lot of experience with diesels, any advice would be greatly appreciated.

 

[Tazza]

I'd like to get the injectors checked/cleaned. The leak could be that the lines are not seated just right. Take the nut off and see how the tube line is sitting on the injector, if it's sitting nice and square it should be ok, buf it it's not square, twist it till it sits right, then tighten it down.
Black smoke is excessive fuel or incomplete fuel burning. I wonder if an injector isn't spraying quite right, so there is unburnt fuel in the cylinder(s) that takes time to burn off.
Even an air restriction can cause this, change or at least clean the air filter.

 

[Madmack]

I'd like to get the injectors checked/cleaned. The leak could be that the lines are not seated just right. Take the nut off and see how the tube line is sitting on the injector, if it's sitting nice and square it should be ok, buf it it's not square, twist it till it sits right, then tighten it down.
Black smoke is excessive fuel or incomplete fuel burning. I wonder if an injector isn't spraying quite right, so there is unburnt fuel in the cylinder(s) that takes time to burn off.
Even an air restriction can cause this, change or at least clean the air filter.

Thank you for your advice. I'll take the injector that leaks out this weekend and take it to the farm implement near my home. If they can't test it for me , maybe they can point me to a place that can? I replaced the air filter when I put the motor in. If worse case scenario the injectors are bad, can I just put new ones in? I read something about new ones might need shims to work properly. Or is that something they do at the factory before they ship them? Thank you again for the advice!

 

[Tazza]

Thank you for your advice. I'll take the injector that leaks out this weekend and take it to the farm implement near my home. If they can't test it for me , maybe they can point me to a place that can? I replaced the air filter when I put the motor in. If worse case scenario the injectors are bad, can I just put new ones in? I read something about new ones might need shims to work properly. Or is that something they do at the factory before they ship them? Thank you again for the advice!

If you get new/reconditioned injectors, they will not sheed shims, as they should be set at the shop.
You can actually test injectos yourself, i have done it before. Take the injectors out, remove whatever tube lines you need to from the pump, connect one back to the pump, doesn't matter where, but as long as you can swing it out and hook up an injector to sit outside the engine, crank it and check the spray. There should be a nice spray pattern, being a 731, i suspect a deutz direct injetion, so the spray should look almost like a star. There should be no drips from the injector either. Soot on the injector could also be a sign of inpropper ignition.
DO NOT put your hands near the spray to check it, oil injection is serious.

 

[Madmack]

If you get new/reconditioned injectors, they will not sheed shims, as they should be set at the shop.
You can actually test injectos yourself, i have done it before. Take the injectors out, remove whatever tube lines you need to from the pump, connect one back to the pump, doesn't matter where, but as long as you can swing it out and hook up an injector to sit outside the engine, crank it and check the spray. There should be a nice spray pattern, being a 731, i suspect a deutz direct injetion, so the spray should look almost like a star. There should be no drips from the injector either. Soot on the injector could also be a sign of inpropper ignition.
DO NOT put your hands near the spray to check it, oil injection is serious.

I plan on working on it this weekend, I'll give that try. If I find a bad one can I replace just one, or should replace all of them? Thank you again for the advice.

 

[Tazza]

I plan on working on it this weekend, I'll give that try. If I find a bad one can I replace just one, or should replace all of them? Thank you again for the advice.

If you find one bad, ideally you should replace or get them both re-conditioned, then you know that both cylinders will operate the same. They are adjusted to open at a set pressure, say 1,500 PSI, the one that is still working may open at 1,300 psi instead due to wear of the spring. It may not be much of a difference, but it could make it shake more than it already does.

 

[SkidRoe]

If you find one bad, ideally you should replace or get them both re-conditioned, then you know that both cylinders will operate the same. They are adjusted to open at a set pressure, say 1,500 PSI, the one that is still working may open at 1,300 psi instead due to wear of the spring. It may not be much of a difference, but it could make it shake more than it already does.

Hey Tazza,
The Deutz is no longer in this loader, he has retrofitted in a V2003T.
I have a question though: What did the Kubota engine come out of?
Cheers,
Derek

 

[Tazza]

Hey Tazza,
The Deutz is no longer in this loader, he has retrofitted in a V2003T.
I have a question though: What did the Kubota engine come out of?
Cheers,
Derek

Ahh, the 2003t will be out of a lter model machine, i thought it had a turbo, i wonder if the issue could be a bad turbo? No boost, it could be over fueling, giving excessive black smoke like a plugged filter does.

 

[Madmack]

Ahh, the 2003t will be out of a lter model machine, i thought it had a turbo, i wonder if the issue could be a bad turbo? No boost, it could be over fueling, giving excessive black smoke like a plugged filter does.

I chickened out and ended up pulling the injector rack and the injectors out and taking them to a diesel shop. They rebuilt the injection pump and tested the injectors. One of the injectors had a stuck pintel. The pump had some bad seals and something had some wear but I don't recall what the parts was? The motor was originally in a Toro groundsmaster 4000D. Thank you for the all of the advice!

 

[SkidRoe]

I chickened out and ended up pulling the injector rack and the injectors out and taking them to a diesel shop. They rebuilt the injection pump and tested the injectors. One of the injectors had a stuck pintel. The pump had some bad seals and something had some wear but I don't recall what the parts was? The motor was originally in a Toro groundsmaster 4000D. Thank you for the all of the advice!

Thanks for the follow up. Glad to hear that you got to the bottom of it.
Cheers - SR