Problems with NOS Cummins 6bta

kev_rm said:

engine won't run 180 off and blowby would not be affected by cam timing.

the video audio sounds like a very unhealthy bottom end to me.

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That was my thought as well.

Only a few of ways to get combustion gasses into the crank case...

Past a piston, through a blown head gasket, or through a valve seal

Diluting oil with diesel, enough to "make" oil is indicitave of a cylinder not firing.

High blow by is indicative of a cylinder problem.

My opinion is to pull the head and take a look see at what is happening. This is assuming that he has already pulled the valve covers and visually checked everything out.

A valve or valves being out of adjustment (tight), while in the extreme can cause a cylinder to not fire due to no or low compression, they won't typically cause a blowby issue since a valve remaining open does not create a path from the combustion chamber to the crank case.

Well actually a valve held open will stop that cylinder from firing, the fuel will run down the cylinder walls into the crankcase (washing off oil too) and the gases will exit by the open valve into the valve cover and pressurize the cc through the oil return passages. Blowby in a Cummins is a given but what that video shows is oil smoke coming out the valve cover. I'm pretty sure it would be darker if it were combustion gases.

Check and correct all the valve clearances first. If all the oil has been washed off the cylinder walls it might be damaged too.

ranger42c said:

What might that nut have been attached to? Or what was it attaching to the engine, if anything? Is that widget still attached? Properly affixed? Sans nut?

-Chris

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It didn't originate in the gear housing. I did a complete inventory of widgets and fastenings. I think I dropped it in. Had stuff spread out around me and was going through some contortions getting the pump back in.

Thanks to all.

I should recap and update.

All timing is fine. I've learned a ton about how these things are put together. Basically worked my way out from the crank through the cam and out to the valves. And IP timing. I really wanted to eliminate as much as possible the possibility that I did unknown damage from the front gear intruder.

Valve train had four intake valves that had no lash. Couldn't find a gap. So I got all the intake valves to spec. Exhaust were close enough and I didn't touch them.

My one nagging doubt is injection pump timing. Everything else I have complete confidence in.

I appreciate the discussion on blowby. I'm well aware of the conventional wisdom. Killed my BT last year. But I think this is a special case.

Remember that this is a motor that sat on a bench for 25 years. Virtually zero hours. Went through a teardown with new rings and gaskets in preparation for commissioning. IP rebuild and injectors tested. And then the motor a dwent through a troubled birth mostly due to my bumbling and fumbling.

So now we're about 25 hours in. I've never been able to get more than maybe 80 hp from it. The blowby as near as I can tell is not cylinder specific.

My take on this is that there's a good chance that if I can get up to full power without much more dicking around the blowby issue is going to disappear. If not we all can agree on the remedy.,

I should also say the the fuel dilation issue appeared to have almost disappeared the last time I was out.

Getting back to injection timing. Tomorrow I'm going to change the oil and filter, clean up, and go out for a quick jaunt around the bay. I've got fully charged batteries, ticking off one of the poor starting checklist boxes.

If i don't see a dramatic improvement I'm going to shut down, lock the IP to TDC, and go back to the pump shop and have them confirm timing.

Hmm. Tomorrow's Friday. Better set an alarm.

Jeff F said:

Hmm. Tomorrow's Friday. Better set an alarm.

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Some people here call Friday "Poets Day" (Piss Off Early Tomorrow`s Saturday).
I hope you solve your issues. I guess we have many many Cummins engined boats on TF, but right now there are 3 with significant issues, that we know about. Probably means nothing.

BruceK said:

Some people here call Friday "Poets Day" (Piss Off Early Tomorrow`s Saturday).
I hope you solve your issues. I guess we have many many Cummins engined boats on TF, but right now there are 3 with significant issues, that we know about. Probably means nothing.

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Actually my pump guy usually works Saturday mornings. 75 years old, same shop for 45 years. I dunno whether they like seeing me coming, but I've enjoyed my several visits there. They now let me near their machines

I really can't blame my issues on the manufacturer, so I think we've got a very low confidence level in any sort of correlation here.

Xsbank said:

Well actually a valve held open will stop that cylinder from firing, the fuel will run down the cylinder walls into the crankcase (washing off oil too) and the gases will exit by the open valve into the valve cover and pressurize the cc through the oil return passages. Blowby in a Cummins is a given but what that video shows is oil smoke coming out the valve cover. I'm pretty sure it would be darker if it were combustion gases.

Check and correct all the valve clearances first. If all the oil has been washed off the cylinder walls it might be damaged too.

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No disagreement with anything you posted except where highlighted.

A valve stuck open will either allow combustion gasses into the exhaust manifold, or the intake manifold, not the crankcase.

A valve seal could be a path between the valve cover area and the combustion chamber but not a valve being held open.

At least thats my armchair troubleshooting from 8,000 miles away

Jeff F said:

Thanks to all.

I should also say the the fuel dilation issue appeared to have almost disappeared the last time I was out

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Just to expand on this - the last time I was out was just before I started this thread. Immediately before that I had reseated the #1 injector. Think I talked about that already. That cylinder had up until then been underperforming the others. It now appears to be better. So there was a noted issue in one cylinder but I think that's been resolved.

Jeff F said:

It didn't originate in the gear housing. I did a complete inventory of widgets and fastenings. I think I dropped it in. Had stuff spread out around me and was going through some contortions getting the pump back in.

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Actually could it have been my 15 mm 1/2" socket? That's really the only thing that I've lost during the commissioning. Wow. Don't think what I saw was that big. But it was definitely shiny.

If I get up early enough I'll do some fishing around during the oil change. Not really fussed about having it (presumably) in the pan, but your questions have rekindled my curiosity.

Pretty sure 1/2" corresponds with 13mm, but it`s still a hard shiny metal object. Maybe the experts can tell if it could get sucked up by the oil feed, and what might happen. I`m never keen on assuming coincidence, if something unusual happened, and a previously well tested engine is doing something unusual, there might be a connection? OTOH maybe it never even made it to the sump.

BruceK said:

Pretty sure 1/2" corresponds with 13mm, but it`s still a hard shiny metal object. Maybe the experts can tell if it could get sucked up by the oil feed, and what might happen. I`m never keen on assuming coincidence, if something unusual happened, and a previously well tested engine is doing something unusual, there might be a connection? OTOH maybe it never even made it to the sump.

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1/2" drive - big hunk of metal.

Ksanders, you are correct, in a dead cylinder, no blowby out of valves unless the guides are shot. I was thinking of my old 944 engine when I had to rebuild its head, it was valve guides. My bad - what you get when you armchair diagnose. Thank you for the correction.

Xsbank said:

Ksanders, you are correct, in a dead cylinder, no blowby out of valves unless the guides are shot. I was thinking of my old 944 engine when I had to rebuild its head, it was valve guides. My bad - what you get when you armchair diagnose. Thank you for the correction.

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No correction here! We're all just armchair diagnosing the problem, praying we are never in the same situation.

Just the concept of visualizing in abstract these things shows how your brain works. Yor are a natural troubleshooter I think.

That's kind - with the possible exception of computer software, I grew up with the attitude that if one human could build something, another could fix it. My huge failing is lack of patience and a diminishing ability to fix things while doing boat yoga.

Xsbank said:

I grew up with the attitude that if one human could build something, another could fix it.

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Me too. Have been mostly applying it to computer software and systems for the last 20 years. I'm actually enjoying this. Building some callous on my hands, doing some wrenching, solving some mechanical challenges, hanging out on my boat, and learning lots of new stuff. I had planned to be in Vermont or Quebec about now, but this is OK too. Maybe I'll still make it. In the meantime, here is this morning's view

Update, since I've directed friends and family here to monitor my situation

Life at anchor is grand. I like where I am and am very protected and secure. Weather is glorious. So rather than try to stick to any aggressive or arbitrary timelines I took a break over the last couple of days. Was just sitting here goofing off with the generator running thinking I should get back to work when the generator started hunting a bit.

I knew that I had some fuel delivery issues early on, but thought I had resolved them. Now I think I need to revisit that. Nothing that can't be done here. Maybe I need a rainy day to spur me into action

"Maybe I need a rainy day to spur me into action "

Or the sound of silence from the noisemaker?

Woohoo! Let's fix the genset!

What is it?

Xsbank said:

Woohoo! Let's fix the genset!

What is it?

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Not broken. I just heard a little sputter at one point that made me think that there still may be some air in the (shared) fuel system.

If I can tear myself away from my computer I'm going to get back at it today.

Update: got a little rain shower and went back at it.

I found air in the loop between the fuel tank and filter. Filter sits below the fuel tank. Interestingly it's happening on both sides. It's possible it's been like that forever, as once cleared there doesn't seem to be any new air introduced when fuel is flowing. In any case I cleared it, pumped a few gallons of fuel through the system and proceeded to the motor test. I'm certain that it's not causing the motor issues so I put it down the list.

Put motor fully back together, changed the oil, bled the IP and injectors, cleaned the bilge. I'm getting good at that stuff.

Motor still doesn't start willingly when cold. Once fully up to temp starting is OK. Could be compression related but also could be timing related.

Went out for about an hour, and nothing has really changed.

Someone mentioned a compression test earlier, and I agree that this might be informative. I am lumping this in with the excessive blowby for the time being, hoping that the conventional wisdom on cause-effect is not necessarily applicable to my case. If I had a tester at hand I probably would have used it by now, but I don't.

So that leaves injector timing. It's possible that the shop has timed the pump to a different mark than the one currently set to on the motor and looking back at my bumbling fumbling unmounting and mounting of the pump I realize that this could have happened without my awareness. There is a pump locking protocol that prevents this from happening, but I didn't follow it. Saw the keyed shaft and in my ignorance didn't recognize the dangers of not sticking to this protocol. I didn't intentionally skip this step, but had some issues with the locking and didn't take the time to repeat the process after I inadvertently unlocked it.

I've read that there is a timing mark inside the pump that can be checked to confirm TDC, but that requires breaking the seal and I don't think I'll go there.

Next step: make absolutely sure pump is locked to (motor) TDC, pull it and visit my buddies at the injection shop. Should be an easy check for them to make. Shop is close to my home and it's about time I showed my face there anyway.

Wish me luck!

Break a leg!

Visit to the pump shop today confirmed that my installation had bad timing - looked like I was 10-15 degrees late from what I could see peeking over their shoulders. That's consistent with the starting and running problems I think.

Rather than adjusting the pump they locked the pump to TDC according to their specs and I'm going to adjust the gear position on the motor to align pump TDC to motor TDC.

Now obviously I could have caught this on day 1 had I locked properly during the pump install. But leaving this aside it would seem that there are some disconnects. Pump shop times to a spec that they get from a computer lookup based on pump number. Cummins specifies a certain timing mark on the gear. My motor is set to timing mark C, and that's what is on the data plate. But service manual says Lucas CAV times to B and C is used for a different pump. Will be interesting to see whether I align to another timing mark. I've read about this happening in other BT installations.

Am cautiously optimistic.

Correction: Lucas CAV normally times to D, not B. That's where I fetched up.

Motor starts fine now, develops full power as near as I can tell, and sounds fine. No noticeable fuel in the exhaust. All cylinders running hot. Now consuming oil rather than making it. Some grey smoke at higher outputs. This after a couple of hours of running at 1800 - 2500 rpm. Am changing the oil just to make sure no remaining dilution and doing a 40 mile run this afternoon, and am still hopeful that the rings will set. Hooked up the CCV and it seems to be handling blowby, but there is still more than there should be.

One more update, and some speculative conclusions.

I've now traveled a couple of hundred miles at a range of speeds since I last posted. Motor starts reasonably well - not easily when stone cold, but it starts. Once started sounds and feels fine to me. Smoke is either non-existent or blue. Occasionally heavy blue. Oil consumption is high. Haven't measured accurately but I'm well into my second 5 gallon pail. Blowby seems to be less, but still significant, some oil coming out of my Racor CCV.

My conclusion when looking back at the history is that I ran the motor for the first crucial hours in a state where there was likely steady fuel washdown due to incorrect timing. I'm coming to the conclusion that a teardown will be necessary to properly remediate the damage. But I've also decided that this can wait until the end of the season. For now I'm keeping the oil topped up and holding onto a faint hope that there will be some degree of self-healing as I operate normally.

This is entirely on me. I've been stupid and negligent in many respects. But it's my motor and it's been a growth experience for me. If I do have the motor out I will try to do as much of the work on it as I can. Not exactly what I signed on for originally, but part of my model of ownership, and could even be fun.

Any further suggestions or experiences are welcome. In the meantime if you see a mainship 34 ghosting by leaving a faint blue haze it's likely me

ps there is a 'bon ami' treatment that I'm thinking about. Think that's probably lunatic fringe territory for most folks here, but I may go there. Will let you know if I do. Google it.

Hmmm. I`ve used Bon Ami to clean windscreens of silicone residue from car washing products, very effective,and no negative effects on the glass itself. I get the logic about fixing glazing on bores, but is that your issue? OTOH, you seem to be looking at a tear down and rebuild, what`s to lose?

BruceK said:

what`s to lose?

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Exactly. Think I'll give it a few days more though before trying it.

Isn't that what the government required to be used to destroy "cash for clunkers " engines ?
Wait for others to weigh in.

"I just heard a little sputter at one point that made me think that there still may be some air in the (shared) fuel system.

I always worry about "shared" fuel systems.