Diesel engine Piston Damage causes?

[kim0663]

I have a small assignment that i need to complete and it goes like this.
I have been given three pistons and i need to find out the cause for the damages occurred.
All damages are fuel related on some way and are diesel engine pistons. four stroke and two stroke.

Piston 1 : is a diesel engine with a concaved? piston head. half of the piston has melted and also, directly underneath the melted portion of the piston has scuff marks.

Over heated? how does diesels over heat with a fuel problem?

Piston 2 : is a two stroke piston. It looks like it has been siezed and has scuffs everywhere from top to bottom of the piston skirts.

Wrong oil/fuel mixture? or extended time of non operation leading to un lubricated bore surface?

Piston 3 : is of a 4 stroke piston and has had a valve brake off, smashing up the piston face. I am not sure if it is a crown type piston that has a combustion chamber within the piston or it has melted after a piece of the valve smashed a big hole into it

What are the causes for valves breaking ? any other than detonation? i also think this is a diesel piston as well... please ignore that hole inside the 'combustion chamber like hole' (or is it?) as it has been drilled after the piston was taken out of the block.


Any ideas or experience stories would be appreciated... I've been researching a bit and have a vague idea of how these happened but i wanted to be sure before i start writing it up...

[barryogen]

rich mixture in a diesel causes high EGT... maybe if it were really rich it'd do it?

[Truenotch]

1 looks like it's dropped a glow plug, 3 could be the same if it's diesel.

2 looks like the piston in my scooter after a friend ran it with no piston for about a month.

[Burning Angel]

1 looks like it's dropped a glow plug, 3 could be the same if it's diesel.

2 looks like the piston in my scooter after a friend ran it with no piston for about a month.

im not sure a scooter would go without a piston, maybe you mean oil?

[evil_si]

#1
over fuelling will cause a diesel to over heat,increases the combustion temputatures, leaking injector or incorrect spray pattern
the over fuelling has cause the piston crown to melt, damaging the skirt and bore, the over heating has also played a part in the scoring on the piston skirt

#2
2 stroke diesels dont run oil in the fuel for lubrication,
that particular piston just looks like its been overheated and picked up in the liner

#3
id say its dropped the tip of an injector and smashed that and broken the valve, the broken piece of valve has done the majority of damage,
and its suppose to have the big dish in the piston

[kim0663]

can they drop the injector tips ?? wow... lol i thought i had done a bit of research but clearly NOT ENOUGH ! keep it coming guys this is great

[finx]

2stroke diesels are bad ass. i have worked on a few. detroit power for the win.
all of the above sounds pritty accurate to me.
i have seen damage done to pistions like no 1 due to people running a dicent mix of petrol in the fuel as well. stuffs with the cetain level and the diesels abitilty to burn/ignite.

[Adamal]

First one looks like it could have been caused by detonation?

[evil_si]

from my experience diesels dont suffer the same detonation effects as a petrol engine,

would also be interesting to know the brand of engines those bits have come out of

[fangsport]

No.1 looks a lot like the last Isuzu diesil i pulled down. holed radiator, but driven till stopped. every piston melted. molten alloy on valves, through turbo and exhaust. didn't seize in the bore once cooled, but obviously tried to seize due to extreme heat.

appears to be a diesil turbo piston.

No.3 appears to have have a foreign object caught between valve and seat, and the piston has come up , made contact and broken corner off valve. the chunk of valve and 'foreign' object have been pummeled between piston top and head/valve.
N/A diesil piston

[Voyeur]

No 1 incorrect spray pattern, directed at exhaust side of piston

No 2 Too lean, faulty injector/pump, blocked filter.

No 3 Mis-timed injector pump