Black smoke after rebuild

[sainted]

Originally Posted by Guy

I'm not so sure. Any amount the valve is open is going to result in just about 0 compression. 200 psi is what 13:1? That is a pretty good valve seal. I don't think the valves are open at tdc.

Having the can timing off a tooth wouldn't cause zero compression, just low compression as pointed out previously. Being off a tooth would cause the valves to upriver too soon or too late preventing a full charge from getting in the cylinders.

[Mithril Bham]

Good suggestions.
Don't know how things work over there but I wouldn't be touching anything. Whoever did the rebuild needs to get it right unless I missed something.

[01kiwijohn]

If the engine was "Bench Run", not dyno'd, then it's fair to assume that it is bolted together correctly; nothing else.
If it is not burping coolant, when it is under load, it is probable that the compression is not leaking out around the head gasket, so the liner protrusion is probably ok too.
Compression, on the low side, can be experienced, after rebuild. My experience has been with the Perkins 6 cylinder engines and I have seen this. Depends largely on the finish of the liners. Put 'break-in oil in it and run for at least one oil change period; it should settle down after that.
Since you have checked all the other items, which would result in some kind of 'restriction', ie: exhaust system, intake system, fuel supply line and filters, then it has to be that the injectors or pump are not calibrated correctly. Either they are the wrong model/size, or the pump was calibrated, on the bench, incorrectly.
One other thing, I once had a 6-354 that had air trapped in the injector pump are, despite repeated "bleeding". But the symptoms you describe don't appear to indicate that being the problem. (No misfire).
When it comes to injectors and pumps, it is well worth the dough to have that work done by a QUALIFIED, PROPERLY EQUIPPED, shop. Franchised shops do cost more, initially, but usually set it up to factory specs and, more importantly, guarantee their work.
"Professional" is only a guarantee that they get paid for their time, not competence.
Surely hope this helps. Don't give up, they are a pretty good engine, really. Let me know if I can do any more for you.

[stepwheel101]

Hi all,
Thanks very much for the warm welcome to cf and all the advice so far… I shall try to respond to your suggestions first.
I did fail to mention in the original post, I have also removed the timing cover, checked that all the dots on the gears lined up, they do; and that no. 1 is at TDC at this point… I have also twice checked valve clearances’; on the first tune I found no. 3 to be a fair way out. All v/v clearances’ are now within tolerance. I have looked at the distance the v/v’s travel in an effort to discount excessive wear of the cam lobes, they all seem to be travelling the same distance so I am fairly sure there isn’t excessive wear there, unless they have all worn uniformly?
I questioned the mechanic and without prompting he told me that he did reassemble with the liners sitting proud, as per specs.
There is no air bubbling out the header tank.
I have spent the last 2 days in the city at the fuel injection calibration shop and at the machine shop that did the rebuild. The latest clue came yesterday afternoon talking to the owner of the machine shop, he informed me that when the engine was reassembled an oil additive (STP) was put in. He believes that this additive may be inhibiting the rings from bedding in?
His advice was to change the oil, and ‘run in’ the engine for approximately 30 hrs and see if there is some improvement. My concern with doing this is I do not know whether or not the additive has glazed or polished the bore/sleeve, and even if the rings do now bed in that the long term life of the engine will be shortened. Having just done a rebuild I would prefer to get it done properly now to maximise my investment. I am also concerned that if further work is needed that undertaking this process may damage the piston rings also.
My instinct is to have the bores re-honed; this could be done without removing the whole engine from the boat, just the head. Obviously being very careful to ensure all loose metal is removed from each cylinder after re-honing. Opinions on this would be appreciated.

Thanks again for all the advice so far, and 01kiwijohn Don’t worry I’m not giving up, I’ve put in way to much time and effort to let this beat me…

Cheers

Steve

[model 10]

There is no honing without taking it all apart again. STP? Idiots. Drain all that crap out and start with 50 hours of break-in oil. You should be fine. Why do people do stuff like that? Do they honestly think Andy Graaitelli was telling the truth?

[beetlejuice30]

Thank you for the thorough update. If the lead enginneer is responsible for the rebuild I would do that!!!
How ever re honing the cylinder would add more wear, I would think.
Just need good cross hatches for the break in. How many hours on the motor before rebuild? New sleeves?
Is the compression still
Low?

Go back to the simple things. This has saved me more times then I would care to admit.


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[jimbunyard]

STP was a bad idea. I'd have to ask the person responsible why it was added.

You can't properly hone the liners without pulling the pistons, it's a little too early to think about that anyway.

I know you clearly said that the timing marks were checked, but must ask if they were checked on all four gears?

How many hours do you have on the rebuild now? If you have access to a borescope, or one of those tiny cameras that you can hook to your computer, you should be able to go into the engine through the injector port and see what the cylinder finish looks like.

Before doing anything too drastic, get the old oil out, flush the crankcase well, and refill with the correct oil only. It may take quite a few hours for the rings to properly seat.

This is going into theoryland, but when I say flush the crankcase well, I'm talking about pulling the injectors, putting into the crankcase a 50/50 mix of oil and diesel, to the proper level, and spinning the engine over with the starter for a couple of minutes, then emptying it out and doing it again (don't overheat the starter), then filling with the specified oil and trying to run it in again. I've heard of people flushing with straight diesel, but that scares me. I've done it with gas engines, the difference was that I ran the engines briefly (5 minutes or so) and then changed the diesel/oil mix. With double the compression in a diesel I'd be leery of running it to flush it, though a case could be made that actually running it briefly with thinned oil could be the more effective solution, because the compression helps force the rings against the liner, scrubbing and buildup off. Really hard to call...

Do not be afraid when running it in, you need lots of RPM (with blips to WOT) and RPM changes at first, but stay away from over 60 - 70 percent throttle under load.

[beetlejuice30]

Just to be clear Iv never used stp as a additive just for assembly. Learned this from a navy chief engineer. just to lube main bearings, rings and any bearings that have to be heated in order to fit.


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[01kiwijohn]

I don't think you need to re hone the bores, at this point. Just add break in oil and then run it at varying loads and speeds until the first scheduled change.
If the rings were as bad as need be to have significantly low power, RPM, and lots of smoke, you'd have noticeable blow-by, out of the crankcase breather. Do you? You can measure it with a manometer, in Inches of water, but I don't think you'll need to be that precise; just visually inspect with the breather open to atmosphere.
From your description, I still lean toward fuel system calibration; whether the pump, or injectors, I can't tell from here. But, black smoke generally means over-fueling.

[jimbunyard]

Also, going from the Perkins service manual forward, the injectors should be:

CAV
Holder: BKB40SD5224
Nozzle: BDN12SD6236

This appears to cross to a Delphi 5352102/HRD145. You need to have the correct nozzles, the nozzle holders are the same.

[stepwheel101]

I hear what is being said re: fuel delivery. I have not discounted this as a cause. What I am lacking is any relyable information on how the pumps should be calibrated? This is one subject that I have found really difficult to get sorted...

[wooden head]

I don't know about the compression issues,but, my first though about the black smoke under load was the fuel may be calibrated for a turbo engine. More air means more fuel. Fuel increase would be under load as turbo spools up.

[jimbunyard]

Originally Posted by stepwheel101

I hear what is being said re: fuel delivery. I have not discounted this as a cause. What I am lacking is any relyable information on how the pumps should be calibrated? This is one subject that I have found really difficult to get sorted...

There are quite a few 4108 owners who are members of CF. Maybe start a thread with something like 'Need 4108 I/P #' and someone can be persuaded to give you the numbers off theirs, and then you can get your pump shop to calibrate it to that number.

There's an instruction book for the CAV DPA pump here:

http://www.bluemoment.com/manuals/Lu...ion%20book.pdf

[shakey doug]

Please post your local air temp along with your starting procedure including times between each sequence. Once the Engine has started take Rpm until it is smoking then the give the Fuel pump a few good clouts with a hammer, if smoke clears when hit the Metering valve or auto advance mechanism is sticking. If no joy try disconnecting the inlet manifold cold start valve feed pipe or take the unit out of the Manifold. Where you situated? Nearly forgot is it a hydraulic or mechanical Govenor f-Pump?

[Wotname]

SD, the OP is located in the Philippines.

Presumably Coral Bay.