Detroit Diesel (DD671N) Questions
 

"Wayne.B" wrote in message
...
On Tue, 24 Jan 2006 19:17:09 -0500, "Eisboch" wrote:

Ain't boats fun?

Eisboch (grandkid #5 is a girl!)

Congratulations! We are still at #0 but both sons are engaged so
that's a good start.

Yes, small air leak is a possibility under consideration. This issue
is fortunately not at a critical state yet but I like to stay on top
of things so I don't get a failure when I'm in the boondocks
somewhere.


Are your 671s turboed or normally aspirated? It's funny when you get to
know how the various engines sound. I can identify the sound of those 671s
anytime I hear them start up.
A friend has a pair of normally aspirated 671s in a 1972 Hat 38 - actually
a conversion from original gas engines. They have over close to 10,000
hours on them and run like a top. Great engines.

Eisboch

Detroit Diesel (DD671N) Questions
 

Wayne.B wrote:

On Wed, 25 Jan 2006 00:31:55 +0100, "Steve Lusardi"
wrote:


I think you should identify symtoms,
if you want meaningful help.


It's a 1981 Johnson & Towers marine conversion, supposedly rebuilt
within the last 1,000 hours or so by the previous owner.

My port side engine is taking longer to cold start than it used to,
sometimes needing 8 to 12 seconds of cranking. It used to start on
the first or second turn even when stone cold, and the starboard
engine still does. If it has been run within a day or two it still
starts very quickly. There is very little exhaust smoke at startup
even when cold, and what little there is goes away quickly. The
engine is running well and making full power as far as I can
determine.


Change the fuel filter, and if that doesn't help, look for a leak in
your supply lines.

--
"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

Detroit Diesel (DD671N) Questions
 

Eisboch wrote:

"JohnH" wrote in message
...

Eisboch (grandkid #5 is a girl!)


Congrats! So what's the score now. I've got 4 grandsons, 1 granddaughter.



Three girls, two boys. Need one more to even up the score.

Eisboch


The M5 makes it an even score!

Dan

Detroit Diesel (DD671N) Questions
 

On Tue, 24 Jan 2006 19:50:34 -0500, "Eisboch" wrote:

Are your 671s turboed or normally aspirated?

Naturally aspirated.

It's funny when you get to
know how the various engines sound. I can identify the sound of those 671s
anytime I hear them start up.

You and all of my neighbors. :-)

It's like having a pair of Greyhound busses idling in your backyard.

A friend has a pair of normally aspirated 671s in a 1972 Hat 38 - actually
a conversion from original gas engines. They have over close to 10,000
hours on them and run like a top. Great engines.

They have a reputation of lasting almost forever and can be totally
rebuilt in place with new cylinder sleeves, bearings, pistons, etc.

It's my understanding that in commercial generator service they
frequently go 20,000 hours between overhauls although 4 or 5,000 hours
is more typical for marine service.

Detroit Diesel (DD671N) Questions
 

"Dan Krueger" wrote in message
ink.net...
Eisboch wrote:

"JohnH" wrote in message
...

Eisboch (grandkid #5 is a girl!)


Congrats! So what's the score now. I've got 4 grandsons, 1 granddaughter.



Three girls, two boys. Need one more to even up the score.

Eisboch
The M5 makes it an even score!

Dan

Ah! The other "baby". Still working on the mandatory 1200 mile break in
procedure.
Pretty much got the hang of driving a manual without a clutch pedal though.
During break in you have to limit max RPM to 5500, so shifts are done around
4000-4500. After the break in period, max RPM is 8200 RPM with shifts around
6500 - 7000 which is getting into the engine's powerband. Can't wait to try
the "S6" mode. This car is going to get me in a lot of trouble.

Eisboch

Detroit Diesel (DD671N) Questions
 

On Tue, 24 Jan 2006 20:15:54 -0500, "Eisboch" wrote:


"Dan Krueger" wrote in message
link.net...
Eisboch wrote:

"JohnH" wrote in message
...

Eisboch (grandkid #5 is a girl!)


Congrats! So what's the score now. I've got 4 grandsons, 1 granddaughter.



Three girls, two boys. Need one more to even up the score.

Eisboch
The M5 makes it an even score!

Dan

Ah! The other "baby". Still working on the mandatory 1200 mile break in
procedure.
Pretty much got the hang of driving a manual without a clutch pedal though.
During break in you have to limit max RPM to 5500, so shifts are done around
4000-4500. After the break in period, max RPM is 8200 RPM with shifts around
6500 - 7000 which is getting into the engine's powerband. Can't wait to try
the "S6" mode. This car is going to get me in a lot of trouble.

Eisboch


Go visit Montana. I understand they're pretty lenient on speed out there. I
rode across the state and didn't get a ticket. That's proof.
--
John H

******Have a spectacular day!******

Detroit Diesel (DD671N) Questions
 

On Tue, 24 Jan 2006 18:59:06 -0600, dazed and confuzzed
wrote:

look for a leak in
your supply lines.

Any advice on how to do that?

Detroit Diesel (DD671N) Questions
 

Wayne.B wrote in
:

Not having made any significant displays of ignorance lately
that I
know of, thought I'd give it a try:

Is there any way to measure compression without removing
injectors or
other major components on DD671s?

Nope. The way to tell if the compression is good is expressed
by:

"Will it start?"

If it starts on all cylinders...compression is great!

Second question:

Since the DD671 is a 2 cycle engine, I'm assuming there are no
moving
valves, just fixed intake and exhaust ports in the cylinder
walls.

No valves. Intake ports and exhaust ports open as the piston
passes over them near BDC when the blower recharges the air and
blows out the dead gases. Piston rises cutting that off,
approaches TDC, cam rack in the head opens injection just as
compressed air reaches 1200F and KAPOW!, we're on our way down
again after this god-awful loud knocking noise also indicating
compression is great, making enginemen smile...(c;



Anyone know if that is correct?

If so, I'm also assuming that any loss of compression would
have to be
from worn rings and/or cylinder bore. Also correct?

Worn rings, cracked cylinder head, cracked cylinder sleeve
usually starting at the port opening. Look at the exhaust. If
it starts steaming after it warms up, the head or block is
cracked allowing pressurized water into the cylinder, which turns
to steam on the hot piston. It always starts cold with white
smoke from incomplete combustion. 2-stroke DDs aren't
"environment friendly"....but owner friendly. Shrimp boats
running 4-53s may not have any rings at all and they're still
shrimping...(c;

You can tell when the rings are "too worn". It starts running
away when lube oil from the crankcase splashes past the worn
rings that are supposed to be wiping it off the cylinder walls
before the big bang....and the 2-stroker just runs away wild on
its own lube oil! Most exciting...black smoke for miles behind
boat...shutting down injection pump makes it go faster! Only way
to stop it is shut off its air supply by plugging up the intake,
which is very exciting on an engine that may explode in shrapnel
any second....(c;

But don't let that prospect bother you putting off that ring job
another year....

At least it'll never have a turbo-charger fire....

Aboard USS Everglades (AD-24), a nice old 6-71 powered a big DC
generator putting out 440VDC for the after gun turret from 1952
that had long since been removed for the stupid DASH helo deck.
(We were better off with the gun because at least it worked.)
The calibration laboratory I worked in needed a stable AC power
supply, even when the ship's AC was awful, so a DC to AC motor-
alternator set, 50KVA was installed and wired into the huge,
black bakelite DC power panel with the huge knife switches no
safety bureaucrat would ever approve of. (The lab actually ran
its lighting off a secondary 110VDC, NOISELESS, winding on the
genset.) The 6-71 drove the AC M-G set to 1800 RPM (60 Hz - 4
poles) any time we weren't parked against Pier Papa in
Charleston. (We used to turn back the speed on the M-G set to 50
Hz so the TV didn't wobble in the Med, under threats of "YOU FIX
IT IF YOU BREAK IT" from the Chief Electrician..(c; That 6-71
had over 12,000 hours on its meter on the panel and would almost
crank by hand! They are really great engines...

Oh, diesel fuel? No problemo. It sucked fuel oil from a 90,000
gallon tank.

Detroit Diesel (DD671N) Questions
 

Wayne.B wrote:
On Tue, 24 Jan 2006 18:59:06 -0600, dazed and confuzzed
wrote:


look for a leak in
your supply lines.


Any advice on how to do that?

visual first, are they wet?
Check all nuts for tightness.
Clamps for tightness,
hoses for leaks or cracks.

It could be as simple as a banjo bolt washer that has compressed....

As I cannot see your installation, I can only give generalities.

I've seen it be as simple as a fuel filter gasket with a small pit in
it. The seal worked under pressure, but left a bit of air into the
system when everything cooled off and the pressure dropped.

Do you have any high points in the system where air could collect?

Do you have a mechanical fuel supply pump or an electrical one?
Hoses or hard pipe from the tank(s)?


If you have a leak, it is currently a small one from your symptoms. If
it was major, you'd have real trouble starting at all.

--
"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

Detroit Diesel (DD671N) Questions
 

"Wayne.B" wrote in message
...
On Tue, 24 Jan 2006 18:59:06 -0600, dazed and confuzzed
wrote:

look for a leak in
your supply lines.

Any advice on how to do that?



Thinking about it, why not just fire up the hard starting engine then, using
a small container of fuel and an acid brush or similar, lightly wet each
fitting on the fuel lines from your Racors forward to the last fitting you
can get to on the engine. Watch for *suction*. Sort of the opposite of a
pressure bubble test for leaks. I don't know if this would work, but it
might. Or, talk to someone who, unlike me, knows what he is talking about.
:-)

It seems logical though that if that engine is otherwise running fine, you
are getting your RPMs and you are not producing smoke more than the other
engine, that a compression problem due to rings or valves is not likely.

Eisboch