Great balls of fire...

[johnl]

Had an interesting experience this morning. Driving home form work in the wee small hours the engine felt less than it's usual self. It wouldn't pull at low rpm and needed a lot more rpm than usual to feel OK. Arriving home it was idling very badly with smoke coming from the exhaust. Too dark to see the smoke colour, maybe oil smoke, maybe fuel smoke, maybe steam...

After some sleep I went to work, thought maybe it might be an O2 sensor issue so had a look at the plugs. All fine except No 4, which was wet and sooty. Tried to start it up, it turned over a few times with no start then suddenly refused to turn on the starter. Not good. Four plugs out again and turned it over again, whereupon it sprayed copious liquid from No 4 cylinder. Instantly I assumed coolant and a head gasket issue, until the fluid burst into substantial flame...

After the fire was extinguished (and heart rate stabilised), very luckily with no significant damage to paint etc (or heart), just a blackening of the bonnet badge and little melting of the plastic cam cover, which appears cosmetic at this point, I lit a smoke and sat down to think this one through. My best guess is that the injector has failed wide open, and is spraying a copious pressure fed stream of fuel for as long as the pump is pumping it.

Spoke to Vlad at Arese, he's sending me a second hand injector tomorrow (will take too long to get e new one in). We'll see.

Regards,
John.

[bazzbazz]

Yup, it doesn't happen to such a degree often, but when it does, as you have found, it is usually in some spectacular form.

When you have the new injector fitted and the engine running just keep an eye out for the signs of hydro lock
damage . . . . . .if the cylinder filled with fluid to the point the starter motor couldn't turn the engine over, and you are truly unlucky, you could find you have a conrod that is less than straight, or big end bearing damage.

Best of luck & fingers crossed.

Baz

[Mick A]

what engine mate?

[johnl]

The engine is a Twin Spark.

Fingers and toes are crossed for bent rod etc. I don't think it was a 'hard' hydrolock, (if I'm lucky...).

I've never come across this before, just the occasional injector that was a little leaky, never one that had turned into a hose nozzle filling the cylinder up.

Regards,
John.

[poohbah]

Crikey John, sounds like you were very lucky to catch it before it really took hold.

As you can see from my car history, I had a similar but slightly more "illuminating" experience that ended the life of my first 156 V6.

Unfortunately for me, the loss of power and subsequent engine bay ignition occurred while I was driving home from work on the freeway. Seems fuel leaked from the fuel rail onto the manifold and up she went. By the time I had pulled off the road and opened the door, flames were already blazing across two lanes of traffic...

[bazzbazz]

Alfa Romeo + Fuel System failure = Spectacular Light Show

It's a simple enough formula to remember, didn't anyone pay attention in physics at school?   

Baz

[johnl]

poohbah,
More than "illuminating" enough for me. In all the many years I've worked on cars this is the first time I really could have done with a fire extinguisher (I'll be checking prices...). I didn't so much "catch it it before it took hold" as much as the petrol just burnt out before anything else caught fire while I was scrambling to find something to extinguish it with...

Your fireball 156 is a sad tale, but at least the car went out in a blaze of glory, the fate I understand of quite a few Ferraris some years back...

My experience has been that petrol can be surprisingly hard to ignite, I've spilled it on hot exhausts with nothing worse than a cloud of petrol 'steam', and seen lit cigarettes dropped into spilled petrol, and just go out. In this case I'm sure it was ignited from a spark from the ignition pack (with a spark jumping to earth through the droplets of sprayed fuel...?)

Regards,
John.

[bazzbazz]

Like most flammable liquid fuels (Gasoline, Kerosene) it is when they are in their gaseous state that they become extremely combustible. A pool of Gasoline is dangerous, but when it is dispersed in a gaseous or aerosol form it is virtually weaponised and will ignite with the slightest provocation, surprisingly, just like what happens inside the engine cylinder.

The spark didn't earth to ground through the fuel, it was just the minute heat source to ignite the vapour, in its aerosol form just a spark from static is more than enough, a lesson pounded into your skull when pumping 19,000Liters under high pressure into F-111s that you NEVER forget!

This is why one should ALWAYS pull the Ignition System relay from the front relay pack when doing compression tests or similar to what you were doing as it deactivates the Fuel pump, fuel injectors and the ignition system.
(Now he tells me I hear you say?) 

And by the way, you're certainly not the first, and definitely won't be the last to fall to this little scenario . . . . .

FYI - One of THE most powerful non nuclear weapon in the US arsenal is the FAE - Fuel-Air Explosives disperse an aerosol cloud of fuel which is ignited by an embedded detonator to produce an explosion.

Check Six
Baz

[johnl]

Baz,
If I had thought about it for a moment (I didn't), and had I suspected the liquid on the spark plug to be fuel (I didn't, though the possibility should have at least crossed my mind), then I would have disconnected the injectors and the ignition. I couldn't smell petrol on the wet plug, but then I'm suffering a bit of rhinitis at the moment, can't smell all that well.

Though I've seen a lit cigarette harmlessly dropped into a petrol puddle (not by me I hasten to add), and spilled it on a pretty hot exhaust manifold without a resulting inferno, I am still very careful with it, recognising some degree of good luck in the above scenarios...

I do know (when I take the time to think about it...) that it's the fumes from the petrol (et al) that ignite and burn rather than the liquid. The idea of a spark jumping to earth through a series of airborne droplets was just a random thought, dismissed as unlikely almost as soon as I had posted it. I'm fairly sure petrol (like all / most hydrocarbons?) is a very poor electrical conductor, even discounting the unlikelihood of an electrical pathway existing in a train of droplets...

Regards,
John.

[bazzbazz]

Though I've seen a lit cigarette harmlessly dropped into a petrol puddle (not by me I hasten to add),

Yes, when things like that happen, everyone tends to HASTEN in all directions as fast as they can . . . . . .

I gotta be honest, I just had a little cartoon pop into my head of you standing there next to the smoking car, face all blackened, hair on end with wisps of smoke rising up from the tips and a little thought bubble containing "Well . . . that was clever!"

Damn I wish I could draw.   

Good luck with the new injector, look on the bright side, at least it's not a JTS!   

Check Six

Baz

[johnl]

... look on the bright side, at least it's not a JTS!   

That's because I did some research before I started looking at 147s, the same reason why I never considered a selespeed gearbox...

Regards,
John.

[kaleuclint]

FYI - One of THE most powerful non nuclear weapon in the US arsenal is the FAE - Fuel-Air Explosives disperse an aerosol cloud of fuel which is ignited by an embedded detonator to produce an explosion.

Check Six
Baz

Oh yeah Baz!!  Not taken on board by the US but employment of SLUFAE definitely part of AS doctrine:
http://www.military-today.com/engineering/slufae.htm
Also handy in the (secondary) infantry role as an improvised direct fire system  .

You wouldn't want it under the bonnet...

[poohbah]

John (et al), you'll be pleased to know that the very first thing I did after acquiring both my GTV and my current 156 was to purchase a fire extinguisher for each vehicle and install it within easy reach under the front of the front passenger seat.

Once bitten, twice shy!

[johnl]

Still waiting for the replacement injector to arrive, hopefully tomorrow. Anyway, pulled the suspect No 4 injector out a few minutes ago, and I can blow through it, so suspicion confirmed.

Also bought new oil and filter. The oil smells a bit petroly, and I have no idea how much fuel ended up in the sump, so new oil is a wise move I think...

Regards,
John.

[johnl]

It was remiss of me neglecting to report that replacing the injector did actually fix the problem.

Vlade at Arese Spares told me that injectors fail so rarely that he doesn't even keep them on the shelf (no-one ever asks him for injectors), so I was more than surprised to have exactly the same thing happen two nights ago with the number 2 injector (first to die was number 4). Same symptoms, the engine lost power (especially at lower rpm), wouldn't 'blip' properly for downshifts, needed higher rpm to perform reasonably OK, and was producing lots of black smoke.

This time I didn't try to turn the engine over until I'd pulled out four plugs, so avoided a hydrolock, and I disconnected the the lead to the coil packs, so avoided setting fire to the fuel when I pumped it out of the cylinder! I also electrically disconnected all the injectors in order to avoid injecting fuel, but stupidly forgot that if an injector is acting like a stuck open hose nozzle it will make no difference whether or not the wire is connected...

Long story short; last time when I ordered a single injector to replace the first dead one, I (eventually) ended up with four still attached to a fuel rail, so more than luckily I still had three good used injectors on hand, so it was quick and easy to get the engine running properly again.

Regards,
John.