It's Dead - Autopsy 080308
Turbo Mini Forums

Gasket looks fine. I don't think that it ever hydrauliced.

There is some very slight damage to the inlet valve seats. Some swarf was left in the manifold after the machining and there was some sitting on top of the pistons. Because the plenum is effectively a closed pipe, it is impossible to get every last trace of swarf out.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I have the same prob with my NA MG 1275. It's blowing between 2 and 3 to the point that it won't start but once it's running it isn't too bad. Head gasket is fine, bores and head is fine but I think my block has gone a bit porus on the deck between the bores.

The valve seats:



The bores:



Still oil in no. 4 after 2 hours.

Edited by Paul S on 1st Mar, 2008.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

is it just an illusion with the oil in the bore that 1and 4 pistons seem at different heights in the bores

cam / chain - valves open so no comp . hard to turn over .

when you revd it and shut off did it back fire etc

There's about 3mm of oil in no. 4. I can assure you that they reach TDC together.

No back fire when I shut it off.

Sturgeo reckons that something is broken in the bottom end as it is so stiff. Even with the plugs out it does not spin as fast as the others with the plugs in. But I would not expect it to get 50 psi oil pressure on the starter if the crank was damaged.

So tomorrow we are going to start getting the engine out.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by robert on 1st Mar, 2008.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

That is really strange...
As there is nothing obviously wrong with the top end or bores, I would make one wild guess from what I can see and those compression readings...
Failed camchain (or even broken camshaft) so the valves were stationary when you did the compression test.
I've only ever seen it once (years ago) but on an A series that had seriously overheatead, but same symptoms.
I hope I'm wrong.

Rod.

Schrödinger's cat - so which one am I ???

No, the valves were moving OK, I had the rocker cover off last weekend and checked, plus the oil pump was getting pressure up.

I don't believe the compression tester - cheap ebay crap. But it tried it 3 or 4 times and got consistent readings. Odd.

I going to check for a broken crank before I take the engine out!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Even stranger....
I'd missed the point about oil pressure so my broken cam chain/shaft is obviously out the window.
Unless the compression tester was totally f****d (so the readings weren't really as low as they seem), the only other thing I can think of that could give seriously low compression readings with all valves moving, no bore damage, no valve damage, head gasket OK etc., is if the timing chain had jumped a few teeth (or one of the keys sheared and allowed the sprocket to move) so the valve timing is way out.
Seen it on a Renault and a Citroen with chain cam drive but never on an A Series.
Clutching at straws really.

EDIT
Can't you try the compression tester on another engine before you go any further to confirm if it is crap or actually telling the truth ???

Rod.

Edited by Rod S on 1st Mar, 2008.

Schrödinger's cat - so which one am I ???

Stating the obvious but when was the last time you checked the tappets? Too late now the heads off but if there was no clearance they could hold the valves slightly open.

Just a guess.

Rob, thanks but I did check the tappets last weekend.

Engine will be out on Saturday.

I still do not know what the problem is. I had convinced myself by Saturday night that the crank was broken, but it seems OK.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Bit of a long shoot but do you have a vernier cam sprocket? if so is there a chance that the locking bolts could have come loose causes in the cam timing to move to the point of unusable?

No, it's basically a standard engine with an SW5 and slightly modified head thrown together on the cheap just to get the car in use and test the EFI.

To make the compression low on 3 and 4 would need the crank to break on the centre journal!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Well I'm out of ideas, looks like you'll have to open the box & see what you've got so to speak.

Have you tried the compression tester on a know engine (as you suspect it may not be brilliant) ???
There is nothing from those photos to say low (next to zero) compression unless the cam timing is way out, well not to my mind anyway..

Schrödinger's cat - so which one am I ???

Paul,

I'm still not convinced it's the crank, having stripped an engine with a two piece crank (didn't know the crank was in two pieces until after it was removed for the engine although knew it wasn't a healthy engine) I can't see how a broken crack would effect the compression test, unless when you turn the engine over only two pistons go up & down, but this can't be the case as when you removed the head pistons 1 & 4 where at the same height as were pistons 2 & 3. Before you rip it to pieces try turning it over by hand, do all the piston move as they should? (I know they did on the aforementioned engine) Therefore if the pistons are moving correctly & the rings are healthy I can see how a broken crank can effect the compression test. Doesn't help much but it may stop you from pulling the engine for no reason. Have you thought about a leak down test? You'll have to put the head back on but that's hardly rocket science? If you've got a compressor you can butcher your cheap compression tester & make a leak down tester for free.

Rob

does this is 20w50 oil you used to test rings?
what does it do if yo put fuel in it instead?

... in fact
I read again the whole thread , and don't think that rings are in fault,
the wrong thing happened when you reved it hard, then cut it,
can you check your cam timing?on your crank pulley 106° is 111 mm from the tdc mark , so your inlet lobe on 1 should be at full lift when this line up with 0°timing teeth on your timing chain cover, this will confirm if you can have jumped your timing chain.
if that's right
then have you a dizzy for test? that's the first thing I would try, plug a dizzy, set it at 20° , it should fire
(if the dizzy drive isn't in place , be very carefull not to let it drop in gear case..., I use a long bolt (lower radiator braket) that I screw in to be sure that it can't fail) .
if plugs are wet and you have a good spark, it's necessary to run, even if you have to put some fuel by hand in the plenum, then you'll know if it's electronic or mecanic related

Bugger, just wrote a long reply and the it did not post. I'll try again later - must go.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Try Again!

Thanks for all the input guys.

The engine is nearly out, just need a couple of sky hooks to lift it clear. Hence, there will be no more testing.

It was haemorrhaging oil and the 998 turbo sits there waiting to go in anyway.

I will carry out a full autopsy and report back.

My theory is that the crank is fractured at the centre main. Under the torque from the starter, the fracture allows some slip, hence, 3 & 4 get to TDC as the inlet valve closes and no compression. The engine then tightens as the crank pushes sideways against the outer main bearings. When the starter stops the fracture returns to its original position.

This engine has always exhibited a high level of vibration. The fact that the Minispares lignhtened steel verto flywheel was not balanced could be the reason why. I guess one too many sessions at high revs broke it. It had been up to 6000rpm regularly doing the siamesed code testing.

This could all be bollocks but I like guessing.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Will be interesting to see what you find Paul, a ball ache for you though.

I'm still not convinced.

But if you've got no compression in cylinders 3 & 4 there are only two options:

1) The engine isn't sucking air in in the first place.
2) Air is leaking out.

It should be quite simple to tell which it is with a leak down test. Got to be easier than pulling the engine.

Rob

PS. You need to treat this from a systems engineering approach. First you need to identify all the items that for the "engine network" then you need to identify the linkages within the network to determine the engine architecture. This won't help at all but that's what systems engineering is about.

Rob, I think that I've covered all the angles. I spent three weekends trying all I knew and the collective input of this post to get it running.

You can dress it up in fancy terms, but put simply, it had fuel and spark and would not run. Time to cut my losses and move on.

The engine was coming out soon anyway to make way for the 998 turbo.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."