Cummins 6CTA8.3M2 Marine Diesel Not Cranking

Dead battery?

(But if you can't even "bar" the engine over, then maybe a more serious problem such as some kind of seize-up.)

The boat is a 52 Ft yacht with fly bridge. Built with the engines inside to never have to remove these. Tight engine room. I found someone with a stronger back who takes over from now. I guess you are pretty close, one of your guesses will be right I expect.

Thank you for the advise. D

Not knowing that particular engine, but... Check engine oil for any signs of metal flakes. A bit on your finger with a flashlight or in the sun. Is it possible to remove the injectors? If so, check their color and/or deposits... Maybe borrow a BoreScope and have a look inside. As mentioned, smell. If all cylinders look the same and not too bad, then then problem could likely be the main bearings. A call to Cummins workshop/service center might help, if they be friendly. If the engine stopped while underway and now cannot be even manually rotated, the picture looks glim. Takes a lot of friction to stop 450 HP. Success

Dear dvmdsc,

You don't say whether there were any previous problems with this engine so I suspect that it ran OK the last time it was run. Therefore the issue of a seized bearing is of a lesser chance that a seized piston. If the engine has not run for some time then the chances are that water has entered the bore and rusted the rings to the liner. It doesn't take much of a leak for this to happen over a few weeks.

Removal of the injectors and a boroscope examination will reveal whether this is a small(or lot) quantity of water in the stuck bore. You will probably find that the stuck piston is around mid-stroke where the torque needed to shift it is at its maximum.

If this is the case yiu will have to decide where the water is coming from ,if its a head gasket leak that is one thing otherwise it may have entered via an open valve exhaust or inlet. If the engine has a water cooled exhaust manifold this is a potential source as they are known to crack., also think about the tubo intercooler as a leak here is also a source of water entering the inlet manifold.

You should be able to do a fair amount of diagnostics before resorting to ripping the thing out.

Don't be tempted to get too physical with the crow-bar as the piston can be damaged.

Once you decide which bore is in trouble removal of that head must be done and having removed any water a liberal injection of diesel oil can help free things off.

If you can access the crankcase and disconnect the big end then the liner and piston assembly can be removed and serviced on the bench; otherwise it will be an engine out job.

Good luck,

Massey

Thank you. This engine still has one big heavy solid head. We will go to the blood, sweat and tears part.

I get the impression that you know and understand nothing about engines, starters and batteries.

If true, go and get a professional on the job before you do even more damage. It will be cheaper in the long run!!

Such problems can generally be isolated by a good professional to the source of the problem within about 10 minutes, just using common sense, previous knowledge and a voltmeter......fixing may take far longer!!!

I think that most points have been stated as to the causes of your dilemma, i.e. piston seizure.

A lesson to be learned here, is that all machinery pressure, temperatures, fluid levels, etc., should be logged at regular intervals, an absolute minimum of twice a day,preferably every four hours.

By doing this this "repetitive" and "boring" chore you may have had advanced warning that something was amiss.

Just one question was the engine set for cruising speed or rated speed (maximum recommended rpm) or at pursuit rating which is a condition of engine overload (generally this may be able to be carried out for four hours in any twenty four period-manufacturers instructions should be consulted for this)

May be a bit of a long shot but did you check the prop to make sure that you didn't wrap something around it and the sudden stopping of the engine created one of the issues already described like a broken piston, piston rod or piston pin. Another area would be you clutch -gear drive area if something froze or jammed during such a sudden stop while "cruising". You may want to investigate under the hull just in case.

If the Prop and gearbox are free turning you need to try and turn the engine by hand /tool with the gearbox in the neutral position. (Make sure the ignition and fuel are off.) If you are satisfied you are getting enough torque to turn the engine but it will still not move(Try both Clockwise & CCW) then chances are the engine is seized and the cause would have to be determined by a qualified mechanic. If the engine is connected to the gearbox by a shaft then disconnect it and try turning engine again just to be sure. If that fails to turn the engine I would concider paying a qualified mechanic to take a look at it in the boat just in case something has been over looked. Chances are you will have to pull the engine out of the boat to fix it. Sorry i couldn't have been more helpful, Good Luck

I have posted before about the gearbox. That has been repaired and replaced and ran on that same engine for about 60 hours now. (some trips to the outer islands)

The gearbox is a hydraulic one and can spin the gears, without engaging the output shaft when in neutral. But nothing happened to the prop drive. The engine is designed for clockwise rotation.

I mentioned turning the engine CCW to see you could, not because I didn't know it runs clockwise. If you could turn it a bit CCW then CW again and it jambs again you could probably count on a broken Connecting Rod. (But it still might be) Because you were told no meaningful information prior to the engine stopping, like any noise or smoke , we all have to make educated guesses and with so little information some of us are going to be wrong, but at least we tried to help. Also I'm sure most of us writers (If not All ) have never set foot on a sail boat that big let-alone been in a sail boats engine compartment so cut us some slack as we try to visualize how it is set up.

We would really like to help you more so you wouldnt have to dismantle the engine or remove it from the boat but with the information and the feed-back you gave us I think you have no choice but to tear it down know matter how difficult it is going to be.

I have a long history with boats big and small, also with broken motors of one sort or other.

It has been the bane of my life that boat designers have no concept of maintenance and repair of the motors they spec for their boats.

That said, if you have enough room to pull the cylinder sleeve out of the top of the block, and the sump off the bottom of the motor then you have a chance of rebuilding it insitu.

If not dig out the chainsaw, this is gonna get interesting..

Here's a thread that might be of help. Has an e-mail form to ask your question to and perhaps they have seen it before or have some better more knowledgeable input.

http://www.tadiesels.com/cummins_6C_engines.html

Your remark had my full interest. In the starter circuit is also a cut off switch. 200 mm2 is already a very respectable welding wire. The isolation mantle is high temperature silicone rubber. This cable will burn down the switch and eventually melt down the starter coils or contacts. I didn't find many posts about crank shaft defects - seized pistons on the contrary I found some. I wait until the boat is lifted out of the water to dismantle the engine block. Thank you.

If the engine is locked up, wouldn't the wire running to the starter overheat and smoke rather quickly ????

I didn't see any mention of the solinoid being looked at ????? Some diesels (catapillar) use 2 solinoids.

As mentioned, yes. Cable or starter can overheat and smoke or contacts can melt down. I didn't wait that to happen.

Thank you for your opinion.

It could still be an electrical problem, starter solenoid burnt out and starter jamming the motor for example.....but we have been given such limited infos that its difficult to be any more exact.......

Andy, I really wish it was an electrical problem. But without the starter in place, The engine crankshaft does not allow me to rotate it even to make me happy. It is definitely a seize up of crank shaft or piston(s).

The weight of the engine is 950 kg. Between the floor (ceiling of the machine room) and the top of the engine is only 8 cm (about 3 inches)

The cylinder head is 6 inches thick (15 cm). Underneath the engine I have 7 cm (3 inches). The hall way between the 2 engines is 2 feet wide and less than 3 feet high.

The diesel tanks and the engines have 8 inches between. (20 cm)

All knee and elbow work. The starter is fine. In a few weeks I will be able to tell more. I ordered a micro camera - will be here in 2- 3 weeks.

Thank you. D

That was not as far as I am aware, mentioned before......thanks for the update.

You will need to make a hole about the size of the engine(s), which the original designer should have made provision for, a sad and serious lapse in the design of the boat. Probably saved a few Bucks.....for the builder.....

"Keyhole surgery" is not safe in a marine environment, the engines may only be 100% correctly repaired, nothing less is serious.....

Then, while the engine is out and being repaired properly, clean up the hole and make a proper and strong, fully sealing strong hatch cover......

Even alignment of the engine/shaft will be a bit easier once proper access is made....assuming that its a shaft system and not inboard or similar.....I am sure that such an access hatch will be most useful even if rarely lifted.

Do not use brass fixings as a friend of mine did on his yacht many years ago, we got over to Holland found the floor of the cockpit was loose!!! a big following sea and we would have been sunk!! I replaced them with stainless steel......and renewed the seal as well....then we filled the cockpit with probably 50 gallons of water and checked for leaks.....

Do not use brass fixings as a friend of mine did................ I replaced them with stainless steel

I take it that the original valves were 70/30 or 60/40 "sh*t" brass valves.........only used in situations where atmospheric corrosion is a problem. I have also seen severe corrosion problems with stainless steel in vessels..........including loss of propellers and propeller shafting.

Your best materials for globe and gate valves in sea water systems are Ni-Al-bronze valve bodies and lids and monel spindles, discs and seats.........expensive? Yes! but they will last the life of the vessel if correctly maintained and serviced.

I was talking about an access hatch to allow proper engine maintenance and removal or replacement if required......in the friend of mine's yacht, it was also the cockpit floor!!

Oops!!............that will teach me to take a little more time reading posts.

Please accept my most humble apologies........bugga!!!!!

I've seen the "Bugga" ad from Oz, I believe it was done by Honda trucks, funny!!

No need for an apology, we have all done it from time to time, its the smallest of problems here, not reading fully......if we call it a problem in the first place.

G'Day.

Er Andy, that was from the "Toyota" ute ads...

The closest thing Honda makes that could be considered a truck is this Piaggio APE inspired vehicle on steriods

Although I see Honda have in selected markets a new fullsize SUV.

The Toyota ad inspired a lot of Toyota ute and Landruiser owners to put it on a sticker (large window covering one) for their rear windows. Some of course are so inspire to put it on upside down.....

I stand corrected, it was a good ad, but some years ago, was NOT seen on German TV, but at least I remembered it was Japanese!!! BUGGAH!!!

G'Day!

I'll give you the solution for a quick spin on the boat!

J/K... I once got a tip from a car guru to help narrow down a search, yank the belt and check each pulley individually to see what locked up.

I wish you the best of luck!

Good tip

Another tip..........I wish you luck!!!!!

Hi as promised more news. Piston 6 has completely molten. What can be the reason (s)?

Hmm, over fueling in that cylinder, either the Injector pump has a metering issue or more likely the injector in #6 is dribbling excess fuel.

I note that Pistons #4 & #5 are a lot sootier than #2 & #3.

Has anyone "monkeyed" with the injector pump settings? I'd be doing a pre-emptive check on the other motor, get the injectors and Injector pump serviced and recalibrated.

I don't suppose someone tainted the diesel with petrol? Or ethanol? you may have to check the fuel in the tanks.

Not being there makes it hard to "diagnose" but that is where I'd be having a look.

Thank you. I have been thinking of a lame injector spring. But still need to test them all. The turbo can make "burn" a serious "overdose" I guess. As far as I know only diesel additives have been used a month ago. The boat made a trip and consumed that "old" diesel fuel already. The Bosch pump has never been of the engine.

Turbo diesels also have either one jet or two of lube oil, directed at the piston base from below.

If this oil spray jet has been damaged/blocked and soes not work as desogned, this will cause piston damage....as the piston will overheat....

Or the jet nozzle may not have been "aimed" as it should either.....you will need to check carefully....

Thanks dvmdsc for the followup. Other than what has been suggested the only other thing I could suggest is the exhast valve spring might be broken allowing (in time)excessive heat buld-up within the cylinder. Good luck.......Please keep us posted....Rescue

What more can one say............bloody Cummins injectors

Dear dvmdsc,

Not a happy picture but one that possibly holds the clue to the cause of the problem. The crown of the piston is well 'cooked' and the uniformity, if we can see it clearly enough, suggests that the heating effect came from a normal injection pattern rather than an abnormal one. On that basis I would suspect the cause lies beneath the piston , namely a lack of cooling. All piston crowns rely upon a flow of oil being projected underneath without which the top surface will overheat and ultimately seize or separate at the gudgeon pin eyes.

Also remember that once the crown overheats it will start to grab the bore and that in turn will increase the heating effect, so it becomes a vicious circle.

I would be looking at the spray jet serving that cylinder before looking anywhere else. A blocked jet or mis-aligned one will cause the same effect.

Interestingly you manged to get it 'home' without it seizing up, I bet things were'nt sounding too good in the engine room as that engine came to a standstill.

Good luck with your rebuild.

Massey.

I got that way before you, see post #43 !! The evening of the say before!!!

Lets see if we are right!!!

Thank you. There were 2 engines. The owner came home on one. GA

Have you checked the exhaust manifold for a blockage on either the exhaust gas side or the cooling water side assuming you have water cooled manifolds which most do. Perhaps due to the recent overall a gasket was improperly located or the manifolds were not cleaned out before re-installing resulting in little or no cooling water or excess heat build-up from poor exhausting of the exhaust gases.