Diagnose my 2QM15?
 

Hi all,

Recently I asked for advice here on my 79 Yanmar 2QM15. Based on advice
here I had the head gasket replaced. A shop inspected the head, but
didn't Xray it, or whatever it is they do. The guy who replaced the head
gasket is apparently at the limit of his abilities, so my next plan is
to have it looked at by a shop. I was hoping I could get some good clues
from the diesel experts here first.

I'm not sure how long the problem I am about to describe has existed but
there may have been versions of the problem present since I bought the
boat a year ago. It has been somewhat intermittent, but seems worse
since the head gasket replacement.

The motor starts hard, but instantly with a squirt of starter fluid. It
runs with a knock at almost all RPMs, but no knock at full throttle with
a little black smoke. After about 5-10 minutes, the power drastically
decreases. It will keep running in neutral, purring like a kitten at all
RPMs, however a fair amount of black fluid pours out of the exhaust, to
float on the water, not much smoke.

Any ideas?

Stephen

In article ,
Stephen Trapani wrote:

The motor starts hard, but instantly with a squirt of starter fluid. It
runs with a knock at almost all RPMs, but no knock at full throttle with
a little black smoke. After about 5-10 minutes, the power drastically
decreases. It will keep running in neutral, purring like a kitten at all
RPMs, however a fair amount of black fluid pours out of the exhaust, to
float on the water, not much smoke.

Sounds like low compression (hard starting) and injector mis-timing.

The black fluid is simply dissolved soot, which could indicate the need
for at least resetting valve clearances when you're not pulling
significant power. Could also mean a burnt valve. Either could cause
hard starting.

Looking again, the new head gasket would require readjusting the valves,
so make sure that's been done.

Using starter fluid is dangerous.

The hard starts could also be from undersized battery or cables, or
slightly corroded connections. We have 1/0 and 2/0 cable runs of less
than 6' and can start with 11 volts. When we had smaller and longer
cables, it took at least 12v when everything was clean and tight. Years
ago, my car wouldn't start due to an extra ohm or two resistance in a
cable connector. Simply squeezing the connector in a vise fixed it for
almost 15 years (Mom's car).

The drastic power decrease after a few minutes could be a mostly-blocked
fuel filter, fuel tank pickup or vent. Change filters, clean the bowls
and see if it still happens. Then open the fuel fill. If still no joy,
pull the pickup out of the tank and see if there's a screen at the
bottom. Remove if there is. Once, I had so many dead critters in the
tank that a straight tube clogged. Siphoned the fuel out of the tank
through a Baja filter (West Marine has a good variant) to give the
filters a break. Luckily, we had less than 5 gallons onboard at the time.

I'd also suspect overheating at full power, except that the alarms
aren't going off. Any change in the reservoir level, day to day?

If those steps don't solve it, I'm afraid you're looking at a rebuild,
but don't start worrying until you've exhausted alternatives, as that's
a remarkable engine from what I've heard.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Stephen Trapani wrote in
:

Any ideas?

Stephen



I assume it has a heat exchanger, not raw water cooling. Fill the fresh
water side with coolant. Leave the cap off the fresh water heat exchanger.
Start the engine and idle it until it warms up a little, but not hot. A
little coolant will naturally escape as it expands. Watch the level with
the cap off. See any massive bubbling, indicating there are hot gasses
escaping from the cylinders into the cooling passages in the head and
cylinder walls? This'll tell you if the head is cracked or is warped
enough to let gasses bypass the head gasket into the cooling system. Not
rocket science, but reliable. No computer is necessary...(c;

Also, note if the engine runs smoother with the pressure cap off it.
Sometimes small quantities of pressurized coolant squeeze their way into
the cylinder as it sucks in fresh air, compress and EXPLODE INTO STEAM
inside the cylinder head as the piston comes up over TDC, making a bad
knocking sound, too! Are you losing coolant for no apparent reason? This
may be why if you are.

Flush out the bilge with fresh water after midnight when the greenies
aren't watching to get the little coolant out of the bilge...(c;

No fun....

--
Larry

It's risky and often counterproductive to look for unseen second
guesses, expert or otherwise, when you are not doing the work yourself
& a shop is about to assess it firsthand. Unless they are grossly
incompetent, the best you may do with other input is to prejudice their
thinking & delay them in locating the real problem, or maybe **** them
off. If you don't trust them you shouldn't call them aboard. BTW a
disassembled & cleaned head is easily & inexpensively inspected for
cracks or similar flaws by penetrant dye-checking, requiring no x-ray.

Larry wrote:
wrote in
oups.com:

maybe **** them
off

You must admit, though, it _IS_ fun to point out the separated wires
leading to the run solenoid....seconds after you look in the hole he's been
pouring over for the last 3 hours...(c;

I suppose if one's idea of fun is a 3 x $80.hr = $240 additional cost
for a small joke, I should be looking for work with these generous,
rich people too. Please send email & plane tickets, I will handle the
rest. ;-)

I have found both as a ship fleet manager/Owner's rep and now a
part-time lowly yacht bilge contortionist, that the very best thing the
Owner or his rep can do in his own interests, is go away after initial
instructions and stay away or shut up until either asked for something
or until the work is completed. Then, if there are 3 hours of excess
charges on the draft account or preliminary bill slip for finding a
fooken wireG, it is dealt with THEN and refused. He who has the gold
makes the rules, not the process. This also avoids all problems or
claims of split responsibility. (i.e., "You are the yard or expert and
I don't think you will prevail in an arbitration over taking 3 hours to
find a solenoid wire with no interference by the Owner and no requests
for further information; I could trace out & draw a whole vessel's
wiring in 3 hours and you owe me dinner for telling you this along with
the reduction, too, plus another $100 for insulting me with your piece
of **** account.") :-)

This works all over the world, and builds good relationships - even
though you will not get the $100, dinner may be a hamburger, and you
know it.

Dave wrote:

On 19 Jul 2005 16:46:14 -0700, said:


Owner or his rep can do in his own interests, is go away after initial
instructions and stay away or shut up until either asked for something
or until the work is completed.

Yes, but it isn't it a very good idea to instruct the mechanics to ask
you what to do you when they know what's wrong and tell you what they
think should be done and what it's going to cost?

And at that point when they ask you that, isn't it a good idea to have
some idea of the likely problems and options? I know I've been in these
kinds of situations before with exactly this boat, I've regretted not
having enough information, and I've loved every time I'd previously had
advice from experts like some of the guys here, and been able to either
trust the mechanic to go ahead with what he thinks, or stop him!


Stephen

Jere Lull wrote:

In article ,
Stephen Trapani wrote:


The motor starts hard, but instantly with a squirt of starter fluid. It
runs with a knock at almost all RPMs, but no knock at full throttle with
a little black smoke. After about 5-10 minutes, the power drastically
decreases. It will keep running in neutral, purring like a kitten at all
RPMs, however a fair amount of black fluid pours out of the exhaust, to
float on the water, not much smoke.


Sounds like low compression (hard starting) and injector mis-timing.

The black fluid is simply dissolved soot, which could indicate the need
for at least resetting valve clearances when you're not pulling
significant power. Could also mean a burnt valve. Either could cause
hard starting.

Looking again, the new head gasket would require readjusting the valves,
so make sure that's been done.

Using starter fluid is dangerous.

The hard starts could also be from undersized battery or cables,

Yes, I have a low battery bank. Old batteries and it turns over fairly
slowly. Once the engine is warm, it starts in a second or two every time.

or
slightly corroded connections. We have 1/0 and 2/0 cable runs of less
than 6' and can start with 11 volts. When we had smaller and longer
cables, it took at least 12v when everything was clean and tight. Years
ago, my car wouldn't start due to an extra ohm or two resistance in a
cable connector. Simply squeezing the connector in a vise fixed it for
almost 15 years (Mom's car).

The drastic power decrease after a few minutes could be a mostly-blocked
fuel filter, fuel tank pickup or vent. Change filters, clean the bowls
and see if it still happens.

I did this all once. Maybe the Racor needs changing? I had the tank all
the way out and cleaned by two mechanic friends.

Then open the fuel fill. If still no joy,
pull the pickup out of the tank and see if there's a screen at the
bottom.

I'm going to call him and ask about the screen at the bottom.... He says
no screen at the bottom.


Remove if there is. Once, I had so many dead critters in the
tank that a straight tube clogged. Siphoned the fuel out of the tank
through a Baja filter (West Marine has a good variant) to give the
filters a break. Luckily, we had less than 5 gallons onboard at the time.

I'd also suspect overheating at full power, except that the alarms
aren't going off. Any change in the reservoir level, day to day?

Reservoir?

If those steps don't solve it, I'm afraid you're looking at a rebuild,
but don't start worrying until you've exhausted alternatives, as that's
a remarkable engine from what I've heard.

Would a diesel needing a rebuild run hard for ten minutes, then lose RPM
and pushing power?

Stephen

Larry wrote:

Stephen Trapani wrote in
:


Any ideas?

Stephen




I assume it has a heat exchanger, not raw water cooling.

It's raw water.

Fill the fresh
water side with coolant. Leave the cap off the fresh water heat exchanger.
Start the engine and idle it until it warms up a little, but not hot. A
little coolant will naturally escape as it expands. Watch the level with
the cap off. See any massive bubbling, indicating there are hot gasses
escaping from the cylinders into the cooling passages in the head and
cylinder walls? This'll tell you if the head is cracked or is warped
enough to let gasses bypass the head gasket into the cooling system. Not
rocket science, but reliable. No computer is necessary...(c;

Also, note if the engine runs smoother with the pressure cap off it.
Sometimes small quantities of pressurized coolant squeeze their way into
the cylinder as it sucks in fresh air, compress and EXPLODE INTO STEAM
inside the cylinder head as the piston comes up over TDC, making a bad
knocking sound, too! Are you losing coolant for no apparent reason? This
may be why if you are.

Flush out the bilge with fresh water after midnight when the greenies
aren't watching to get the little coolant out of the bilge...(c;

No fun....



--
Stephen

-------

For any proposition there is always some sufficiently narrow
interpretation of its terms, such that it turns out true, and
some sufficiently wide interpretation such that it turns out
false...concept stretching will refute *any* statement, and will
leave no true statement whatsoever.
-- Imre Lakatos

Stephen Trapani wrote in
:

It's raw water.



Sorry............................Yecch.

--
Larry