D950 one cylinder white smoke on start-up

[awitty]

I did a part rebuild of my d950 (rings and rod bearings) and she smokes like hell and misfires from one cylinder (no 2) at start-up. After about a minute or so the smoke stops and it runs fine.

I know the smoke is unburnt fuel. So I'm thinking it's either compression, the injector or valve lash. However I've check all three and still can't find the problem.

The compression is good, perhaps even slightly better than cylinder 1 or 3.
I've swapped the injectors around and no difference.
I've checked the valve spacing numerous times.

Any other ideas? I was thinking of removing the injector pipes as see if the squirt out of injection pump differs to 1 & 3.

Have I missed anything else?

 

[North Idaho Wolfman]

Glow plug

 

[85Hokie]

so.... what were the 3 psi measurements ?

and what the cold lash? something like .008?

the fact that it clears up is a good sign to me..... but does not point to a specific problem - but the engine warming up MUST help the situation.

checking the pipes would be easy enough and made provide a clue - I don't think that is the problem however.


EDIT - wolfman nailed it

 

[North Idaho Wolfman]

You could do a fountain test on the injection pump, but what your describing is not under fuel, but over fuel or unburnt fuel problem.

 

[awitty]

When I had the injectors out I did check the glow plugs and they all quickly went red hot when I switched them on. But I haven't swapped them around so I will give that a try.

 

[North Idaho Wolfman]

If the PSI of the cylinder is good, then your only other option besides the glow plug is a leaking or too low pressure popping injector.

 

[awitty]

Well it's not the glow plug. It tested fine and cylinder 2 is still smoking after I swapped them around.

Here's a little more background information.

Prior to replacing the rings and bearings the engine was always hard to start. I bought a cheap compression tester and all 3 cylinders were reporting somewhere between 100-150psi. I know this is very low as the factory spec is (337-448psi). However I assumed my tester was inaccurate as from what I have read it shouldn't even fire with such low compression. It also didn't appear to be low on power when used although there was a fair bit of blowby.

Nevertheless I decided to replace the rings & bearings and also checked the cylinder bores etc were all within manufacturer tolerances etc.

Post rebuild the compression I get for each cylinder is as follows;

1 = 310
2 = 320
3 = 310

So a significant improvement but still below spec, but I put this down to my testing equipment. Furthermore the cylinder 2 has the problem, and that has the most compression.


Today I decided to remove the injector lines so I could see what the injection pump was spitting out. I've spent quite a bit of time working on a d1105 injection pump so I was expecting to see fuel hitting the garage roof. However, all 3 was only shooting the fuel about 10cm in the air. Could this be my problem? Although it doesn't explain why cylinders 1 & 3 are ok and 2 is ok after it's warmed up.

Any advice appreciated? I suspect you will all say compression, but that doesn’t make much sense to me given the history above - and I really don't want to have to open her up again :-(

 

[TheOldHokie]

Well it's not the glow plug. It tested fine and cylinder 2 is still smoking after I swapped them around.

Here's a little more background information.

Prior to replacing the rings and bearings the engine was always hard to start. I bought a cheap compression tester and all 3 cylinders were reporting somewhere between 100-150psi. I know this is very low as the factory spec is (337-448psi). However I assumed my tester was inaccurate as from what I have read it shouldn't even fire with such low compression. It also didn't appear to be low on power when used although there was a fair bit of blowby.

Nevertheless I decided to replace the rings & bearings and also checked the cylinder bores etc were all within manufacturer tolerances etc.

Post rebuild the compression I get for each cylinder is as follows;

1 = 310
2 = 320
3 = 310

So a significant improvement but still below spec, but I put this down to my testing equipment. Furthermore the cylinder 2 has the problem, and that has the most compression.


Today I decided to remove the injector lines so I could see what the injection pump was spitting out. I've spent quite a bit of time working on a d1105 injection pump so I was expecting to see fuel hitting the garage roof. However, all 3 was only shooting the fuel about 10cm in the air. Could this be my problem? Although it doesn't explain why cylinders 1 & 3 are ok and 2 is ok after it's warmed up.

Any advice appreciated? I suspect you will all say compression, but that doesn’t make much sense to me given the history above - and I really don't want to have to open her up again :-(

In perfect shape these machines are plain dirty at startup. I have a B7200 that has been similar for many years. If it clears up shortly after cold start up relax and use it.

Dan

 

[awitty]

In perfect shape these machines are plain dirty at startup. I have a B7200 that has been similar for many years. If it clears up shortly after cold start up relax and use it.

Dan

Alas I couldn't possibly do that :-( My inquisitive mind won't let me rest until I understand what's going on. Bedside's I enjoy troubleshooting. It's a great way to learn!

 

[North Idaho Wolfman]

There is nothing wrong with the injection pump.
The pump output you see is normal.

Have you had the injectors properly tested?

Did you do anything to the head?
Could be a valve stem seal leaking oil.
Does it have blow by?

 

[awitty]

There is nothing wrong with the injection pump.
The pump output you see is normal.

Have you had the injectors properly tested?

Did you do anything to the head?
Could be a valve stem seal leaking oil.
Does it have blow by?

Thanks Wolfman.

I've not had the injectors properly tested, but I did try a new injector from a good source in the UK that didn't fix the issue.

HOWEVER..

It does have a bit of blow by and I did change the valve stem seals. Could this by my issue? Have I misdiagnosed fuel for oil .

 

[Henro]

Alas I couldn't possibly do that :-( My inquisitive mind won't let me...Bedside's I enjoy troubleshooting.

In so many words Dan said: Just use it!

It seems like your issue is a minor one. Major issue, different story.

Sometimes it is beneficial to take the practical approach and let the inquisitive mind rest a bit.

BUT if you are having fun, why change your approach?

Many of us get our fun out of using our tractors rather than working on them...well I guess we do get our fun while working ON them...

 

[North Idaho Wolfman]

How long have you run it since your re-ring?
Did you hone the cylinders?

 

[awitty]

How long have you run it since your re-ring?
Did you hone the cylinders?

Not very long. Maybe a couple of hours. I did hone the cylinders

 

[North Idaho Wolfman]

You might just need to run it a bit to get the rings to fully seat.
And how do you know it's just one cylinder?
Are you running it with the exhaust manifold off?

 

[awitty]

You might just need to run it a bit to get the rings to fully seat.
And how do you know it's just one cylinder?
Are you running it with the exhaust manifold off?

Ok. Yes I took the manifold off so I could see what was going on.

You don't think it's oil/valve stem seals then ?

 

[North Idaho Wolfman]

Ok. Yes I took the manifold off so I could see what was going on.

You don't think it's oil/valve stem seals then ?

Oh it could be, but it could also be that it just hasn't fully seated the rings.
You can have good compression and have a bad / Non seated oil control ring.

 

[awitty]

Oh it could be, but it could also be that it just hasn't fully seated the rings.
You can have good compression and have a bad / Non seated oil control ring.

Ok. Thanks for your help. I'll report back once I've done some further checks

 

[North Idaho Wolfman]

Ok. Thanks for your help. I'll report back once I've done some further checks

Sounds good

 

[Fedup]

As much as I hate to start another "slingin" storm, it's my opinion that simply "re ringing" a diesel engine is usually NOT a good idea. I know some (possibly many) will disagree, citing all sorts of good results doing just that. In my experience honing or deglazing used liners or cylinder walls isn't likely to produce a truly round bore, only a slightly larger (and still uneven) one. Pistons, if the skirt wear is really minimal stand a better chance. Particularly so if the ring lands are truly "good as new".

It's something I've always stayed away from, only going there if that's what the person involved wanted and was satisfied that the result was not likely to be "like new" performance.

That said, having only a couple hours run time on new rings (most of that probably just monkeying around with this smoke problem) and not yet really putting it under load long enough to seat the rings isn't help much either.

As has been stated, you should probably run (and WORK) it a little more and stop fooling with it until you determine you really have a problem. I would also suggest you verify the temperature gauge is working properly before doing so. Breaking in and seating new rings can generate more heat than expected, which can undo all your efforts so far in short order.