Utoh, I might have done a bad thing...

[lostmarbles]

so, if I plumb the breather into the intake, are we thinking run-away is a risk, or no? ..............

.....But you'll be fine with a breather routed to the intake......

But I have heard of diesel engines self-destructing after roll-overs (by sucking in their own engine oil and revving to their limit until something breaks or until bearings seize.) So under what circumstances does this happen???? (Or did I just imagine hearing of these events?)

I have just proven for myself that "foot-off-the-accelerator" (closed butterfly valve in the intake manifold) does NOT prevent my diesel engine revving up to its limit. (I did this simply by momentarily removing the vacuum hose from my injector pump diaphragm while the engine was idling.) So a diesel certainly doesn't need much air to achieve combustion.

Furthermore - Turning off the ignition key (moving the arm on the injector pump to the fuel-shut-off position) won't stop it either if it is breathing in engine oil.

So - If my vehicle were to roll onto its RH side where my breather is located, and I had plumbed it into the air intake...... Would I not run the risk of the rollover causing my engine to self-destruct?



If I rolled my BJ I would probably be happy for it to self-destruct anyway cos I wouldn't want it anymore. (I've already rolled one 4x4 and I never managed to get its body panels to fit properly after that.)

 

[Dougal]

But I have heard of diesel engines self-destructing after roll-overs (by sucking in their own engine oil and revving to their limit until something breaks or until bearings seize.) So under what circumstances does this happen???? (Or did I just imagine hearing of these events?)

An engine running inverted will kill itself quickly anyway. Probably siezing due to the oil being in the wrong place, but if it takes a large volume of oil into a cylinder then it'll hydraulicly lock, damaging itself and stalling.

The only risk of runaway is a continual feed of a fuel volume large enough to provide enough to provide power, but small enough to not lock the engine.

 

[amaurer]

I can't quite get my head around how a diesel can run off of fuel in the air stream to begin with; seems to me if you add fuel on the intake stroke its just as likely to ignite before TDC as afterwards. You'd be relying on crank momentum and slow burning fuel to keep things moving; is the right combination easily achievable? It seems precarious to me.

 

[Dougal]

I can't quite get my head around how a diesel can run off of fuel in the air stream to begin with; seems to me if you add fuel on the intake stroke its just as likely to ignite before TDC as afterwards. You'd be relying on crank momentum and slow burning fuel to keep things moving; is the right combination easily achievable? It seems precarious to me.

You are correct.
The preignition results in heavily advanced timing which makes the engine run really rough and vibrate lots.
If you've run propane into the intake of an idling engine, it gives exactly the same symptoms, but the propane is slightly worse as it's a faster burning fuel.

 

[lostmarbles]

........The only risk of runaway is a continual feed of a fuel volume large enough to provide enough to provide power, but small enough to not lock the engine.

And it would be quite possible for this "metered quantity" of oil to be fed into a diesel's air intake by an "engine-breather-vented-into-the air-intake set-up" while the engine is lying on its side ---- would it not Dougal?

(Well this is the scenario that I think is possible anyway.)

Can anyone vouch for having seen this happen???



PS. Perhaps this is yet another reason why "positive air shut-off" is now considered a better way to "kill" a diesel than "fuel shut-off".

PPS. We already know that fumes near oil wells can provide an alternative source of fuel (for a diesel motor to run out-of-control on)and that laws usually require "positive air shut-off devices" to be fitted to diesels operating in those environments.

 

[Dougal]

And it would be quite possible for this "metered quantity" of oil to be fed into a diesel's air intake by an "engine-breather-vented-into-the air-intake set-up" while the engine is lying on its side ---- would it not Dougal?

If a vehicle is lying on it's side, most oil breathers would be running uphill or downhill.
If it's uphill for oil to get to the engine then the engine won't get much.
If it's downhill then the engine will probably get a lot.

Any volunteers to test these theories.

 

[lostmarbles]

Hey thanks for this thread Amaurer. It has had a very positive spinoff for me.

Ever since we bought our "used Japanese import" Nissan car it has leaked oil on our driveway. Since it was leaking at either end (both the front pulley and bellhousing drain hole) your thread made me start thinking about "excessive crankcase pressure". So I tracked down a hose that leads from the rocker-cover into the air-filter box. Sure enough - a felt pad (through which the fumes enter the airbox) was almost completely clogged with oil and carbon/soot.

I've cleaned that out and enlarged the entrance hole. And I'm pretty sure I've greatly reduced the drip rate. (Too early to say whether I've eliminated it completely.)

And that car has messed up our driveway for years now!

Call by for a free beer or two as your reward

 

[eleblanc]

Did your catch can had a opening to the atmosphere? you can't send blowby into a sealed can obviously. And IMO that can seems just too small.

 

[amaurer]

glad to hear it marbles!

eleblanc, yes, it had an opening to atmosphere, also 1/8" ID. My boneheadedness DOES have limits you know...