Monday, February 24, 2014
Sunday, February 23, 2014
RUNAWAY DIESEL
Ever since I was a kid,
I've been fascinated by things that blow up. When I was barely a teenager, I
blew up the garage. I was unsupervised and messing around with some powerful
chemicals. As a parent, I can see clearly now that I should have never had
gotten my hands on them. One rainy day, in my garage laboratory, I was mixing up
combinations of powders to make a home-made bomb. The Potassium Chlorate is very
unstable stuff. The result was a blown up laboratory and permanent injuries. Now
I confine my fascination to store-bought fireworks.
I may like explosions,
but there's one kind that I hate, and that's when an engine blows up. And,
exploding engines can be very dangerous to life and limb. They can throw large
masses of metal with great force. Everyone in car racing knows about a scatter
shield. One of the most feared truck engines with the worst reputation is the
Detroit Diesel which has massive flywheels that have been known to fly
off.
Actually, it happens in
three states. First, a linkage problem throws the engine into an uncontrolled
free rev -- full throttle. The linkage for the rule rail is very tricky. This
can easily happen when the fuel rack control rods jamb -- holding the fuel rack
wide open. The first thing a student in diesel truck school learns about this
engine is the importance of the fuel control rods.
If you get them installed
wrong, they will jamb the throttle resulting in a ran away. And because this
engine has this tendency, it comes fitted with a "Slam Door" and a big heavy
metal door that is built right into the intake air box. If the engine starts to
run away, you can crop the slam door and close off the incoming air, and kill
the engine. At least, that's the idea.
But, it doesn't always
work. They don't call them oil burners for nothing. By having the habit of
feeding on its own oil, the Detroit
engine is one of the worst offenders. The reputation partly comes about because
that engine is a two-stroke. It has ports on the sides of the cylinder lines for
air intake.
This is important here,
because it provides a place for the oil to be introduced into the engine. If the
air box gaskets are weak, they will be sucked right into the screaming engine.
This unwanted source of air will allow it to keep running away. Then it begins
feeding on its own oil as superheated oil, which is being pumped past the rings
into the combustion chamber, fuels the fire even more.
Finally, it runs out of
oil and seizes up. That's what launches the flywheel, the crankshaft suddenly
stops turning and something's got to give! The flywheel bolts shear off, and the
massive fly wheel comes crashing right out of the bellhousing.
But that's nothing new to
race fans. Exploding clutches have brought the requirement for scatter shields
on race cars. I guess it took enough severed legs to find out the need for this
protective 'device. But there is nothing to protect you from the flywheel off a
runaway Detroit Diesel. I've heard that the massive flywheel will go through
concrete walls.
And what a noise it
makes! It's one of the most terrifying sounds in engine can make. When I say
screaming, a runaway Diesel is louder than a speeding train engine. And, at the
same time, it belches smoke like a blast furnace. I happen to know firsthand,
because I had an opportunity to witness one that ran away. It happened while I
was attending night school for heavy-duty mechanics at Sequoia Diesel
Institute.
One of the students
jammed the rack levers on a Detroit Diesel and the engine went full rev as soon
as it was started. The teacher pulled the lever for the slam door, and the
engine slowly died. But for one terrifying moment, it. screamed and roared like
a metal monster gone amuck. That's when I first heard the story of the runaway
Detroit Diesel flywheel busing through walls. The teacher saw it happen. The
engine ran away, exploded when it seized up. The flywheel came off and went
through three walls before coming to a stop halfway into a fourth.
And that was where I
learned about CO2 fire extinguishers. The teacher explained that in case the
slam door didn't stop the runaway, we should use a CO2 fire extinguisher to stop
it.
Since CO2 doesn't burn,
it stops the engine dead in its tracks by starving it of oxygen. It's quick,
efficient and works every time.
Years later, while I was
wrenching for a Mercedes-Benz dealership in Palo Alto, I was instructed on the
MBZ way of shutting down a diesel engine. According to factory protocol, the
proper method is to open the fuel injector high pressure supply lines, starving
the engine of fuel. While this worked okay, it was really messy and takes up
valuable time. And when an engine is at full-rev, every second counts. First,
you had to find the correct wrench size for the injector fuel lines. Then you
had to break them open one by one, which creates quite a mess. Diesel fuel
spurts over the entire engine compartment.
You're probably wondering
why MBZ diesels run away. First, they rarely throw off their flywheels and
seldom explode. But, it can happen in one of two ways. The first is when the
throttle linkage sticks. This isn't much of a problem as long as you keep the
ball-sockets properly lubricated. MBZ fits the engine with a shut-down lever
that looks like a choke knob. Also, located right above the injection pump, is a
manual fuel cut-off device. But, modem MBZ diesel engines use a shutdown system
that's operated by the ignition key. A small vacuum motor mounted on the rear of
the injection pump performs the shut down.
The second way is when
the vacuum motor diaphragm ruptures. The owner find that the only way to shut
down the engine is to get out, open the hood, and press the manual shut down
lever. Not the sort of thing that MBZ owners could be likely to do, huh? Well,
the replacement of the vacuum motor can be tricky. It has a small tang on it
that must catch in a notch on the injection pump rack. If it doesn't, it'll jamb
the rack in a wide-open-throttle position and bingo, "Runaway
Diesel."
And it happened right
next to me at the MBZ dealership where I worked in Palo Alto. The tech next to
me was installing a vacuum motor and didn't' get the tang right. This launched
the engine into a screaming fit as soon as he started it. And while he was
making a mad dash for his toolbox to find a wrench to open the injector lines, I
grabbed the CO2 fire extinguisher from the wall and shot it into the air intake.
The engine's screaming died right away, even before he got the
wrench!
He stood there amazed.
And when the engine stopped, so did all the work in the shop. You could hear a
pin drop. Everyone was looking at the two of us as we stood there. Me with the
fire extinguisher in my hands and the tech with a wrench in his. That's when the
stop foreman got involved.
He came storming over
shouting, "What the hell do you think you're doing?!" I replied in as calm a
voice as I could muster, "Just a trick I was taught a Sequoia Diesel." "Oh
yeah?!" he shouted back at me. "You just ruined this motor with that stuff." he
said as he began removing the air filter, expecting to find it full of
something. When he lifted the metal cover, it revealed what looks like snow
piled up going into the air filter -- nothing more. He reached over
and touched the frozen
CO2 as it rapidly disappeared into wisps of smoke. He said in a caustic tone as
he turned and walked away, "Well that may be so, but we don't do that
here!"
The only diesel to run
away on me happened when I was working at Larry's Autoworks. And it scared me
big time! I was doing a major service on a Peugeot 504D. It's a pretty
straightforward diesel engine, there isn't much that you can do to hurt it. But
I did find one Achilles heel. The air filter uses foam that resides in an
oil-bath housing. The foam stays wet by the oil bath, which is an old method
used by trap dirt.
And when I cleaned the
foam, I make a big mistake. Unknowing, I cleaned it in the parts washer solvent
and didn't dry it before installing it. Oh sure, parts solvents works really
well at removing grease. But, it became trapped inside the foam. Since it was
combustible, it caused the engine to run away for a brief moment. I remember
standing there, not knowing it happened. It was over so quickly.
But, for just a brief
second, I thought the engine would explode and I would be killed. And it was all
over, and after careful checking, there appeared to be no damage. I didn't say
anything to the owner, for fear of losing my job. Well, I thought I had gotten
way with my mistake until the next day, when the Peugeot showed up on a tow
truck. When I saw it, my heart sank. I feared the worse: a blown engine.
Actually, it only wouldn't start.
The compression was
excellent, and nothing mechanical appeared to be amiss. Further checking
revealed that all four glow-plugs had been burned up by the solvent's fiery
blast. Because it had warmed up when I worked on it, the problem didn't show up
until the next day, when it was dead cold. Here's when I needed the glow-plugs
to start. All it took to fix it was a set of glow-plugs.
But by far the worst
story I know about an exploding engine happened on a diesel-powered car. Those
of you who have been around the diesel engine trade know about the horrible
automotive diesel engine that GM made. They modified the 350 gasoline engine to
run on diesel. Big mistake. It was never designed to hand that kind of
compression or torque. When trying to get one to start, a mechanic was shooting
ether into it. The engine exploded, blowing off of the cylinder heads, which
dismember one of the mechanic's arms. But that's another story.
Monday, February 17, 2014
Saturday, February 15, 2014
THE 308 TIME BOMB
bomb." It would run perfectly for several months and then, boom! It would blow
the catalytic converter right off the back end of the vehicle. When the catalyst
exploded, it would do so with such force that nothing but the header pipe would
be left. The rest of the fragments would become roadway shrapnel, never to be
recovered.
The foreman who was assigned to the problem had seen it through the first three
catalytic converters. The car was still under the five year/50,000 mile
emissions warranty, so the dealership kept having to replace the catalysts.
There never was enough of the catalyst left behind to give a clue as to what
caused the explosion.
After the car came back with its fourth exploded converter, the foreman was told
to assign the job to another mechanic. The foreman, Willis, didn't want to give
up the car, telling his co-worker that he never could make it happen. "I drove
it and drove it. It never acted up. I think the owner is nuts. I think he is
taking it out and going over a hundred when it happens. I can never find enough
road to get it over 60, at least not around here."
It was true. Traffic on the busy Hollywood 101 freeway made it nearly impossible
to attain speeds above 60. Why did the car have it in for converters? It was as
if the car was a wild stallion that refused to be tamed by a catalyst. The 308
engine had a continuous fuel-injection system with two separate ignition
systems, one for each bank of cylinders.
Ace, the next mechanic on the shop totem pole figured the problem had to be
related to the ignition system. He remembered how Dan, his high school friend,
used to get going about 50 mph and turn off the ignition. Just before the engine
died, he would turn it back on. Bang! It would make a terrific explosion and
scared the daylights out of the girls. Finally the muffler blew apart.
Systematically, Ace went over each connection in the primary ignition system. He
tested every connection and everywhere he looked everything was in perfect
order. He was looking for something that was loose, or a connector that had
backed out of its holder. He reasoned that vibration was causing a harmonic to
develop in the car and the wiring harness was breaking down somewhere.
Finally he worked his way back to the car's computer, which was located in a
side panel in the trunk. As he removed the computer from its moorings, the
engine faltered for a second. Every time he wiggled the connector to the
computer, the engine faltered. Aha! It must be a faulty wiring harness.
He proudly showed the foreman what he had found and was told to order a new
harness. Before he placed the order, he decided to test the multigang plug on
the computer side of the harness. It was just a hunch. Maybe the connector on
the computer was the cause, not the harness. Ace's hunch was right on the money.
The computer connector had a cold solder joint and was making intermittent
contact.
When the driver got the Ferrari going fast enough, a harmonic vibration was
created in the rear end that was sufficient to cause the connector to open up.
When it did, the ignition system would shut down. Since the car had a mechanical
continuous fuel-injection system, fuel continued to flow. In the time it takes
to blink your eye, the catalyst would fill up with a perfect mixture of fuel and
air. When the computer made connection again, spark came back and the engine
started firing again. Nanoseconds later, flames from the exhaust would hit the
converter and BOOM!
"But why couldn't we duplicate the problem on a test drive?" asked Willis, the
shop foreman. The owner finally came up with the answer, "Because it always
happened late at night when I went from San Francisco to Palo Alto... at speeds
between 100 and 150 mph."
Monday, February 10, 2014
Sunday, February 09, 2014
The Salesman and his Magic Beans
Many things have shaped my career as a mechanic. I remember when I took a
job in the only sports car shop in town because I was tired of turning a wrench
on ordinary cars. Or maybe it was because I had fallen in love with a '58
Afla-Romeo-Giuliette-Sprint-Veloce and my Bertone-bodied mistress lured me into
the world of exotic cars. Anyway, this is a university town and there are plenty
of rich kids with sports cars. And a large number of tweedy college professors
who bought weird cars in Europe and shopped them home. I was challenged by the
Alfas, Austin Healys, MGs, Jags and all the rest. It seemed pretty classy to a
twenty-year-old used to working on 36 HP Beetles for $3 an hour.
I still remember that rainy, damp, bone-chilling morning. The weather was giving
me a real feeling of what it must be like to live in England. I struggled to get
the engine and tranny out of a Sprite in order to change a 2-dollar carbon T/O
bearing, when a 50's Port Hole Buick honked its horn to enter the shop.
Little did I know that my whole life was about to change. When I opened the
door, the mist and fog swirled around the old Buick as it rolled inside. The
driver was a little old man with skin so yellow and thin you could almost see
inside him. He reminded me of one of those visible anatomy plastic models.
Barely taller than the rear-view mirror, he couldn't have weighed more than a
hundred and ten pounds--but he had the loose of a salesman.
"Hiya, boys!" he said as he plucked a cigar as big as a grease gun from his
mouth. "I wanna show you boys a few products that are gonna make you some
money." Oh no! He was a salesman, and I had let him in! Dave, Carl, and Don
walked over to stand beside me, all of us instantly mesmerized by the appearance
of this little man.
"I was a mechanic myself once," he said as he tossed a yellow plastic thing with
wires toward us. I instinctively moved to one side as Dave picked it out of the
air. It looked like one of those Mausers that all the bad guys carry in old
movies.
It was shaped like a pistol, with a trigger, a couple of switches, and some wires
with alligator clips on the ends. It was the kind of thing that would get you
thrown in jail if you took it through airport security. The little guy reached
back into the old Buick and brought out a small plywood box. He walked around
front and placed it by the right wheel. In a flash, he was on top of the box
with the hood up. Then he snapped his fingers twice. Crack-Crack! The sharp
reports rattled off the shop roof like shots from a .38!
The strange yellow device flew past my face again, this time headed in the
direction of the old guy. He caught it in his left hand, and in one fluid
motion the alligator clips popped out between the bony fingers of his right
hand. It was like watching a magician. "This boys, is a Snappy--a patented and
registered trademark. I invented it. Now I'm going to teach you how to make
money with this indispensable and highly scientific diagnostic instrument.
This is a tool no mechanic can do without."
"The red and black leads are connected to any 6 or 12 volt battery--red to
positive and black to ground--except for old Fords and English cars. The
orange clip goes on the solenoid feed wire."
"On GM cars it's the purple wire that runs across the firewall. My special
wire-piercing device on the clip allows you to connect it without crawling
under the dash. The green lead goes to the coil primary. In a minute, I'm going
to show you how to check coil polarity using my Snappy and an ordinary pencil."
He went on for more than an hour as we learned how to test for bad grounds,
locate opens, check fuses, and bulbs. It was strange, because none of us had
said a single word since he and his old Buick rolled through the door.
"Since you guys have been such good listeners, I'm going to make you a special
deal." Four left hands reached for their wallets. "No! I don't want your
money...not until I show you my newest invention, he said as he puffed his
cigar--which was now so short he had to spit it from his lips. "Sorry!" he said
as he ground out the butt with his black and white oxford.
"After many years of experimenting--Ya know, I worked for the War Department
during the big one, I have finally perfected a chemical method of replenishing
the metal that wears from the piston rings and cylinder walls of internal
combustion engines."
His eyes began to bug out, and the veins stood out in his neck. He talked faster
and faster with his arms waving as he told us the details. It seemed that the
oil companies were out to get him. They were trying to steal his invention
before he could get a patent on it. From the cavernous trunk of the Buick, he
produced a small cardboard box. It was filled with five small flat brown
cardboard packages that looked like patent medicine boxes. He slid open one of
the packages and in it were twelve big, round, bean-like capsules. They looked
like worm pills you might give a horse.
"Got an oil burner?" he asked. "A real smoker?!" I opened my mouth for the first
time in more than an hour. "The Vauxhall," I blurted.
Dave shot me a threatening glance and Carl's eyes rolled back in his head. We
all knew the Vauxhall had been run out of the water and ruined the rings on a
couple of pistons. This little 4-door car parked in a back corner of the shop
had a forlorn look about it, its narrow fenders appeared kind of hunched around
the grill--reminding me of a cowering dog.
"Start it up!" he commanded. I jump in it. It cranked real fast for a long time
before catching, and then billowed heavy blue smoke from the tailpipe. The smoke
hung heavy in the air, drifting up towards the shop roof, giving the place the
air of a Civil War battlefield. The Vauxhall panted and shivered as it idled on
two cylinders.
The little man had a smile on his face, as if he knew something we didn't. He
let it run for a minute and then instructed me to shut it off and remove the
spark plug. He saw oil fouling on #3 and #4 and shoved one of his beans into
each spark plug hole. He then asked me to start the engine. The longer it ran,
the smoother it idled, and smoke stopped coming from the tailpipe.
"The Snappys are five bucks each," he said as he threw us each one. "I'll be
back through from Chicago in a month. Try the Beans...and we'll settle up then."
He jammed another cigar in his face, jumped into the Buick and slammed the door.
I could see him stretch to reach the pedals. The starter cranked a half-turn and
the straight-eight ticked over almost silently. As he backed out into the fog, the
Buick disappeared like the Titanic, without a sound. I'll never forget that day,
March 20, 1964. A month passed. Then summer came and went. So did Vietnam. But
the little old man never came back. For the longest time I expected to see him,
just barely peering over the steering wheel, every time I saw an oval-port
Buick.
The years drifted by. Recently, I thought I saw him driving a new Park Avenue.
Have you ever noticed that when you owe someone money, you think about them? I
mean, it's unfinished business. Maybe the oil companies DID get him or was it
the cigars? I've still got my Snappy as a reminder that it wasn't just a dream.
Oh, and those magic beans? But, that's another story.
Thursday, February 06, 2014
Denso cabin air filters
Both are Denso cabin air filters that fit the same cars. Which one is new? Top or bottom filter?
Answer: Both cabin air filters in the pictures are new Denso cabin air filters that fit the same cars. The filter in photo B. is a Carbon Filter and the visible black material
is the carbon for trapping noxious gases.
Monday, February 03, 2014
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