It's actually a flywheel from, of all things a Japanese ( not Chinese ) engine.
Over here in the U.K. they are becoming more and more prominent and are now appearing for various overhauls in our workshops.
You can see the balance drillings, ringear and the Spigot location hole in the photograph.
So this engine runs ok for several days and then goes down to Limp O .
It's a high speed diesel so you would think that by going onto Limp O the fault should be pretty obvious.
So out with several types of FCR and attempt to fault code read the set up to at least show the area in which the fault lies.
NCS, no codes stored on any of the FCR used.
Where to go from here?
Anything show here?
Goes onto Limp O mode when?
Initial start up?
No load situation?
None of these but someone remembers apon initial start up rev. counter works initially then packs up.
Ah you think.
Rev. Counter piggy backs off the CAS. ( crank angle sensor )
So let's start with that.
Scope it, it's the Hall effect waveform pattern, i.e. Square waveform depicted.
Funny pattern displayed where the reluctor plate gaps are, not normal pattern showing.
Some of the square waveforms where dropping to earth show a ragged line instead of a clean right angle cut off.
Out with CAS and observe resin type face containing fine windings is chipped, but how is this?
What's happened here then?
Further investigation reveals the 24 V starter motor has recently been changed.
It's a two stage bendix and the outer one has let go the Bendix.
Looking at the old motor ( made in China says the badge ) I see the spring steel circlip ( actually a C clip ) has let go.
This sits in a machined groove around the inner shaft where it secures it to the armature rotor output shafting.
Being spring steel the clip bouncing around in the bell housing has obviously done some damage.
Camera in the CAS hole doesn't really show a lot with the injectors out and barring the engine over slowly.
So off with the new starter and barring it over the end elevation of the reluctor plate teeth show damage and maybe some missing as the teeth gap seems large.
Not done this operation on a Japanese engine before so really not quite sure about this and how wide the reluctor plate gap should be.
Contacting the dealer for exploded view of the reluctor plate and separate ringear to shrink on he doesn't know what I am talking about.
Bolt on reluctor plate?
Shrink on ringear?
Don't know about this he says, have to come back to you, got to do some research on this, haven't had this happen before.
I make the decision to remove the flywheel and all is revealed.
There is no bolt on reluctor plate.
There is no shrink on ringear.
It's a one piece machined jobby.
The missing teeth are part and parcel of the flywheel reluctor teeth, no sprocket as the teeth are not sprocketed to take a chain but square so the CAS can count them whizzing by and supply the necessary info into RPM, injection timing and so on.
Got to buy the whole lot. No wonder the storeman can't ID it all, it's not available separately.
Complete with Spigot bearing, lock device and new torq bolts.
No of teeth missing I can't believe it even ran at all never mind not throwing up any fault codes.
So button it all up, erase the non existent codes and flash it up.
Runs ok so job done.
Two days time MIl ( management indicator light) comes on and it's down to Limpo mode again.
I have long gone past the "can't believe it " stage with all this common rail stuff, as I have always said you never, ever say that's it, job done guaranteed unless you want to commit financial suicide.
Back to the ship, FCR it and although no fault codes were present at all on the previous visits up comes P242
Now P242 means DPF problems ( Diesel Particulate Filter ) and the oxy sensors in the exhaust system indicate " excessive ash buildup in bank One. "
Off with the exhaust and uptakes shearing off nearly every nut/ bolt in the process but luckily none in the Exh. Manifold.
Observe it's really choked and the backpressure must have been way excessive.
Beat and bang it and like the old days decoke it all without damaging the No One Exhaust bank.
Back together, new studs/ nuts / bolts and joints, flash up, knock out the MIL light and although this was a week ago no MIL light on and no Limpo Mode present. ( as yet anyway )
Now why were these symptoms not present first time round?
Why nothing and yet clearly displayed the second time around?
Research indicates that this system has an automatic DPF set up and it will retard the injection timing and lift the RPM up to overheat the engine and blow all the crap out of the uptakes when excessive back pressure is indicated.
Delving further into the why's and wherefores all is revealed.
The CAS doubles up as a Rev Counter and as the Rev Counter only flicks up on the initial startup then drops to zero the engine requires a working Rev Counter to complete the DPF cycle and no Rev Counter equals no DPF operation.
As to why it didn't show first time round?
Nothing unusual here, it's Common place with all this CR diagnosis for one defect to hide behind another.
So one defect caused another, again symptom V cause situation.
So well done to DW and BP, could be a opening here for you?
But it's a new type of windup technology here and not, as I have observed many times popular with many fully skilled people particularly members of the old school who don't like to be associated with " repeat " jobs or indeed " since you " jobs accusations levied by people whom really don't know what the score is with CR or indeed understand how it all works.
So to the criticisers / disbelievers slip the cover off the ECU just after shut down and pass them that Capacitator with a straight face.
Should keep them fully charged all through the next day to say the least.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.