Entabeni
WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
From Entabeni: 2006 Pajero 3.2 DiD LWB GlS Auto Gen3.

As far as I can establish piston failure is a common problem with these motors (as well as some Isuzu motors). The cause appears to be 'over-fuelling' by the injectors when they grow "old", i.e. over 100,000 km. Then a very hot (and possibly off-centre) flame can develop which over-heats the point it strikes to the extent that it can melt the alloy. Furthermore, a specialist diesel and turbo firm in Worcester says that they have seen pistons completely shattered by explosive burning caused by over-fuelling. This may well explain the 'pinging' sound which I and others on the Forum have heard.

These direct-injection injectors have to cope with the extremely high pressures of the burning mixture during the power stroke and are mechanically complex. They say that the various operating pressures on mine were way out. It cost just over R 4000 to have them reconditioned! Nevertheless, take action before you find yourself stuck in some remote place, for that would cost a lot more! It is just damned lucky that mine failed 20 km from home so that I could drive it back without further serious damage.

With mine stuck in a carport behind our house in Robertson I have relied on the Haynes Repair Manual for Pajero models 1997 to 2009 to guide me. In the section dealing with possible repairs with the motor in the vehicle, they include removal of pistons. It has taken me four weeks to get to that point, even though I have done this kind of thing many times for more than 50 years with a variety of more conventional petrol vehicles! The Haynes manual does not get everything right and glosses over many procedures that require cranked spanners not to speak of cranked wrists. Difficulty of access is the main problem. I will post further items on the Forum, with photos, describing some of the procedures. Meanwhile here are some photos of my failed piston No 2 with its crack and possibly a minute amount of melting. (Have failed to upload them --- will try again)

Finally, does anyone have new pistons for sale?

Entabeni.
WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
What you describe is an injector problem, not a piston problem!

The injector is the problem / cause, the piston is the victim / result!

With your permission, I will change the title of your thread to "PISTON FAILURE due to FAILED INJECTORS".
Gerhard Fourie
If you want to shoot somebody, make sure you aim at his head, not your own foot.
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andrew.ashton
WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
There is a fascinating book about piston failure here: Piston damages - Description, assessment, causes.

Unfortunately I can't cut and paste from it (it is a secured pdf), but section 3.4.2 is headed Material removal / fusion due to melting on the piston crown (diesel engine).

In essence an injector that cannot maintain pressure after the normal injection process has ended can reopen because of injector line pressure transients. The extra fuel, now in the absence of oxygen (because all the oxygen got burned in the normal diesel ignition cycle) ends up flowing towards the outer edges of the piston and forms glowing spots of burning fuel. The material under these spots softens and the force of combustion gasses drags off small particles, finally ending up in a holed piston.

There is also a section 3.4.3 Cracks in the piston crown and combustion bowl recess. Again these can (not always) be caused by faulty injectors resulting in high localised thermal cycling.

I guess when you have these hot spots, there is the likelihood of precombustion (pinging/knocking). Although that can be caused by other factors such as mechanical pump timing etc.

I think the lesson is that if you hear pinging on your diesel powered vehicle you must consider it abnormal and get it attended to by a knowledgeable diesel operation ASAP.
Entabeni
WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
From Entabeni,
Another try at uploading photos of the crack in my piston.
Attachments:
Rear gudgeon socket 25%&20x.jpg
Piston rear 25%&20x.jpg
Piston top 25%&20x.jpg
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WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
Eina!

Those injectors don't fail as often as you would think.

Mimmo posted this a while ago


___________


I had my pump and injectors tested by Alan Black at 650,000 km for the first time and they apparently are within specifications. The paj does not smoke and the fuel consumption is the same as when it was new,
approx 10.5 to 11 liters per 100km.........

Mimmo

____________

and also

____________

I have always used 500ppm diesel ( mostly BP ), additives never used , fuel filter replaced every 20,000km ( original mitsubishi filters always used ).Engine oil used is Caltex delo 400.

Mimmo

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WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
How would you describe pinging? (ie how different is it to turbo whine?)

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Karl

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WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
Gemaskerde Tuinvurk wrote:How would you describe pinging? (ie how different is it to turbo whine?)

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Pinging oin a diesel better known as diesel knock.

Start an old isuzu 280 in the cold and that rattly sound of the diesel knock is what pinging sounds like.

Almost sounds like there is a nut being thrown around in the combustion chamber.
Re: WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
On my 2001 LWB DID it sounds the same as for a petrol engine. Mine has been doing so from day one when you put foot and labour the engine, specialy with a trailer in tow. When you ease off on the foot it dissapears. Does not sound like diesel knock as from my Toyota D4D when cold, for me pinging is not the common diesel knock I know, it happens whwn the engine is warmed up, could also be when cold but I doubt if you would hear it.
Entabeni
Re: WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
Gemaskerde Tuinvurk wrote:How would you describe pinging? (ie how different is it to turbo whine?)

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From Entabeni,

Thank you for your reply G-T,
The sound is not a whine at all but more like a hammer hitting an anvil, when going up a medium gradient --- but the sound is not quite as sharp as that. I found that going out of cruise control or lifting my foot slightly off the accelerator pedal stopped the sound. Hope that helps.
Re: WARNING: DiD PISTON FAILURE DUE TO FAULTY INJECTORS
Entabeni wrote:
Gemaskerde Tuinvurk wrote:How would you describe pinging? (ie how different is it to turbo whine?)

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From Entabeni,

Thank you for your reply G-T,
The sound is not a whine at all but more like a hammer hitting an anvil, when going up a medium gradient --- but the sound is not quite as sharp as that. I found that going out of cruise control or lifting my foot slightly off the accelerator pedal stopped the sound. Hope that helps.
I have a sound (for the past 70k kms) like that, but I've asked Mitspro and Allan Black about it and they reckon it's the normal turbo whine...

You blokes make me worry! :p

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Karl

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