Stuck diesel fuel injector causing crankshaft to break??
Stuck diesel fuel injector causing crankshaft to break??
(OP)
On a Detroit diesel "Series 92", will a stuck fuel injector cause a crank shaft to completely shear off? The break occurred just 2 inches back from the damper.
The engine had 25 hours use on it from an "engine rebuild".
It was at my work so I do not know all the details of what was done to the engine.
The engine drives a 150 kw generator.
When I got back to work, the generator had a failure. When we took it apart we discovered that the exciter armature had been rubbing against the stator and grounded out. We sent it away suspecting a cracked or bent shaft caused by the crank when it broke.
So my question is, has anybody heard of cranks breaking because of sticking injectors of a diesel?
The engine had 25 hours use on it from an "engine rebuild".
It was at my work so I do not know all the details of what was done to the engine.
The engine drives a 150 kw generator.
When I got back to work, the generator had a failure. When we took it apart we discovered that the exciter armature had been rubbing against the stator and grounded out. We sent it away suspecting a cracked or bent shaft caused by the crank when it broke.
So my question is, has anybody heard of cranks breaking because of sticking injectors of a diesel?





RE: Stuck diesel fuel injector causing crankshaft to break??
Was the crank replaced or just refinished during the rebuild? Replaced with a reman crank? 2" from the damper is probably about where the damper bolts end...
RE: Stuck diesel fuel injector causing crankshaft to break??
Crankshafts are pretty stout on the 92's. I would take a very close look at that damper. If it's the same as trucks, it is a viscous unit. Look for ANY sign of fluid seeping out. Shake it and feel if anything moves inside. Look for any dents. If you find anything wrong with the damper it could be your problem. Also check the front pulley for major runout.
Otherwise, someone probably installed a crank that was not fully inspected and just waiting to let go. I highly doubt it was from any problem with the fuel system.
RE: Stuck diesel fuel injector causing crankshaft to break??
"When the Eagles Fall Silent
The Parrots Start Jabbering".
W. Churchill
RE: Stuck diesel fuel injector causing crankshaft to break??
The damper was checked by the mechanic after the fact and he said that it was good. Our chief engineer checked it also and said it was good. The damper was replaced regardless.
I am not on ship for another month and by the time I get back it would be Xmas so I don't think I can get a pic. Sorry.
RE: Stuck diesel fuel injector causing crankshaft to break??
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Stuck diesel fuel injector causing crankshaft to break??
To the latter - not by my guess. Even if the engine were running in the "worst case" condition continuously, it'd probably take a couple hundred hours or so.
RE: Stuck diesel fuel injector causing crankshaft to break??
For all those doubting that a period of 25 hours isn't enough to cause a fatigue fracture:
I assume the installation is running in the US? at 1800 rpm?
25 hours x 60 minutes x 1800rev/min = 2.700.000 cyles. Tha's the number of rotations. Since a crankshaft usually failes to a higher order frequency, multiply that number by the critical order numner. More than enough to cause a fatigue fracture.
RE: Stuck diesel fuel injector causing crankshaft to break??
RE: Stuck diesel fuel injector causing crankshaft to break??
Still, it was intended to show the number of cylcles you get after "only" a number of hours or days.
RE: Stuck diesel fuel injector causing crankshaft to break??
That's not true, it's also dependent upon the shape of the cylinder pressure traces (harmonic content and amplitudes), which is related to engine load, injection timing, duration, etc. Engine load will be related to electrical load, and will likely fluctuate.
In the case of misfiring due to electronic problems, it is not uncommon for a "bad" event to happen once every few minutes, rather than once per firing cycle, with cyl. pres. excursions on the order of 2x normal (bust your pressure pickup and hear it outside the test cell type pressures). This usually shows up in busted rings, bent rods, etc., a while before the crank lets go.
In the case of a stuck-closed injector on an I6, I wouldn't really have expected the crank to care. On larger gensets (16-24cyl), a single dead cylinder can have terrible implications for crank vibration (and analysis is often done for a particular application assuming one dead cylinder at a time up and down both banks, with a damper selected to help overcome the worst scenario).
A bad coupling could conceivably be a problem too, but I'd guess this application uses a single-bearing genset with a fairly stiff (torsionally) discs-o-steel flex-plate coupling.
RE: Stuck diesel fuel injector causing crankshaft to break??
I'd look for an defective vibration damper, as misfiring conditions are usually part of a torsional vibration calculation and this more or less rules out problems due to misfiring (provided a calculation has been made).
unless it is a common rail engine, injection timing and duration is fairly constant and independant on load.
RE: Stuck diesel fuel injector causing crankshaft to break??
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Stuck diesel fuel injector causing crankshaft to break??
BTW, 92's are V configuration not inline. To further answer Greg's question, it is not rare to have a mechanic steam clean an engine and get water into it. This was an especially big danger on the pancake (sideways) mounted engines. I've seen at least a dozen engines hydrauliced. In every case but one, it bent a rod or two, or three. When pretzled good enough they take a bite out of the liner or cylinder wall while they're at it. In the one other case the starter gear broke. Never saw it break a crank. Leave it running while cleaning!
RE: Stuck diesel fuel injector causing crankshaft to break??
Admittedly the higher harmonics are of small amplitude, but they are there.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Stuck diesel fuel injector causing crankshaft to break??
RE: Stuck diesel fuel injector causing crankshaft to break??
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Stuck diesel fuel injector causing crankshaft to break??
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Stuck diesel fuel injector causing crankshaft to break??
It's a 2-Stroke so it is supercharged. But Detroit blowers are gear driven from the big mass of gears that drive everything else.
Could be too that the previous owner of the crank had something incorrect at that end.
Detroit cranks "look" right, wear like diamonds, and are durable as all heck. But I've seen many more of them break for no apparent reason than other brands. Perhaps they are too hard, or perhaps it's because they are a 2-stroke.
RE: Stuck diesel fuel injector causing crankshaft to break??
V-8 blown 2 stroke engine that has a 150 kw generator driven by rear of engine.
I do not know the extent of the rebuild done on the engine.
Both generators in the ship were done at the same time. Both engines only drive 150 kw generators and have no accessories attached to them. There are 2 other detroits in the engine room that handle stuff like fire pump and bow thruster etc.
The second engine did experience a leakey front crank seal about 250 hours after the rebuild which we replaced.
I do not know if the engines were even taken out of the ship.
I wonder if someone did not jack up the engine by the damper in effort to get more room from the engine and the bottom of the bilge.(Naw, to crazy)(Although I admit doing it to car engines in my younger day)
I think I will assume that the break did not come from the stuck injector and it did come from some abuse to the front of the crank or a failed damper.
They are old engines and who knows where they have been.
I have only been on this ship part time for 3 years and the history of equiptment is unknown to me.
Thanks for all your input.