Diesel diagnostics help...PLEASE

[Allure2sail]

Hi:
This M12 in my 27 has been a struggle from the day I bought the boat.
At first it would overheat so I changed the following:
Thermostate replaced (twice) rated at 165 degree
Heat exchanger (boiled out and tested to be clear)
Raw water pump replaced with a rebuilt Sherwood
Raw water strainer replaced with a new Groco
END RESULT:
Motor now ran to cold actually never above 130-135 degrees
The bigest problem then was that the motor above above 2100 rpm started to spew allot of black smoke.
I was told by two diesel mechanics that the injectors were bad and it was dumping to much raw fuel when I throttled up and that it was actually cooling off the cylinders with the extra fuel that was not being burnt off. Over the winter I removed and had the injectors tested and they were junk as expected. Bought two new injectors and also glow plugs (why not!!) and the motor temperature wise now runs at 175-180 degrees as it should....great. Problem I still have is the black smoke above 2200 rpm. I was told that the injector pump might be out of time or perhaps the mixing elbow on the exhaust might be carboned up. When I took a close look at the mixing elbow I could tell it had been replaced recently.....so that is low on the probability list. As an added piece of info I did add some LUCAS injector cleaner last fall before I pulled the injectors and it did make the engine run hotter, 160 to 170 degrees. I have purchased a diesel compression tester but have not tested it yet, was told the compression should be at least 300 psi (but per ferably in the 325 to 350 psi range). As far as the injector timing has any one on this site gotten into timing or at least checking the timing of the pump? Anyone out there got any knowledge on these symptoms?
Thank you in advance for any help you may render.....
Bruce

[breeze]

Bruce,
The black smoke is often from the diesel being over loaded leaving unburned fuel in the cylinder.
Will the diesel run above 2200 rpm without smoke with no load?
If so you might need to take a 1/2 pitch out of the prop to let the rpm's come up.
David

[Allure2sail]

Hi:
It will rev above the 2200 but it starts to smoke and it just looks nasty. The prop is a 12 x 9 but I do have a 12 x 8 that is on my "parts boat". Interesting.....do not know which is the proper prop for this combination. Does one half or one degree really make that much of a difference? What do the other 27's with the m12 engine have for a prop from the factory? Did not think it was worth changing the props for one degree less pitch......perhaps I was wrong. Anyone know what is the proper pitch?
Bruce

[bob lamb]

Bruce;
  Here's a web site that may have some answers for your problem: 
   http://forums.torresen.com/sailing/

BobL

[Craig Weis]

"Let me wade in here. I am not diesel smart so expect any of this to be wrong...based on some basic diesel knowledge let me say this about that." That is my disclaimer!!

1~At "2,200 [engine rpm ] but it starts to smoke and it just looks nasty" Yep your making the churn do too much work trying to turn that prop [through the reduction gear] at what ever the prop rpm is.

You ought to endeavor to calculate the engine and prop rpm through the whole range. How fast are you turning the engine, how fast is the prop turning? What's the reduction? How many lb of thrust, or tons of water are moving to move the CP-27 through the water? And at what speed? About hull speed? Bare in mind that for every lb of thrust at the keel about 15 lb of thrust is generated by the sails. So says my Naval Architect Tim Graul.

There is a basic physical reason why propellers will never be driven through a speed changing automatic transmission, like on a car. If that were even remotely possible our 107 ton, 150 foot Palmer Johnson Yachts would have been fitted as such rather then fitted with Twin Disc reduction gear boxes. Our Mann Twin V-16, 4000kw [13,648,000 btu, or 1,109 hp] engines could be more fuel efficient.

I cut grass with a New Holland TS 110 tractor with 21 foot Alamo flail mower. And when I hit the dense grass she barks, and belches black smoke as the turbine pumps in a bit more air/fuel mix to maintain 1,900 rpm.

The heat of compression fires the diesel fuel so when started cold she ought to be exhausting a grey colored exhaust till the combustion chamber warms up and atomizes the fuel, then she ought to be 'clean burning' with little visible signs of soot [smoke] until pressed into service. Think about those unlimited tractor pulling beasts. The only limits on these are the amount of fuel/air that can be pumped into the chamber. And the exhaust is so thick you'd swear that anyone could walk on top of the cloud of black smoke. Point being...she works, she smokes. There is no unburned fuel in black smoke. Just a rich mix to make power and upping the temperate of the motor. Interestingly enough because the Germans had limited oil in WW II, but a lot of coal, they actually flew a four engine aeroplane bomber on pulverized coal. The experiment was a failure only because the delivery of this 'powder' to the engines was never satisfactory perfected.

2~No need for a compression tester. It either compresses till fired or not. No need to clean out the down stream exhaust unless the internals are wet and greasy, that makes the carbon. She either flows or it does not.

3~Fuel pump injector timing is all crucial and is variable as to rpm just as firing is variable with engine speed in a gasoline engine. That shows up as a sweat running engine or a bear that seams to want to pound it's way out of the bottom of the hull.

4~Temperature; I'm just thinking out load here but I'd try a thermostat on the engine AND on the heat exchanger. Variables are the water temperature of the sea you floating in, and the work the engine is doing. My 1959, SCCA-A Sports Race-Austin-Healy 100-6 with the Ford V-8 289 race motor and T-10 transmission had a Hewey helicopter engine oil cooler on it and that was fitted with a thermostat. So the running temperature was rock steady under all load conditions. One of my dad's houseboats was fitted with twin 383 cu in engines and velvet drives 'tween the churns and outdrives. These were cooled with a engine water heat exchanger and a engine oil heat exchanger. To be honest I can't say if the coolers had thermostats but I know the engines had normal engine thermostats. Our biggest cooling problem was stopping to remove the enormous number of used protectives [rubbers] that plugged up the raw water filters in the Chicago River, dammed up and made to run backwards into the Illinois River and into the Mississippi to the Gulf. Well at least some people in Chicago were praticing safe sex.

5~Change the prop. Probably over propped.

skip. 

[Salty19]

Like skip, I know little about diesels. 

But I think his suggestions are very good ones.

Look into the duty cycle of the injectors. This is the amount of time the injector nozzles are open for every instruction by the electronics to open.  Longer duration duty cycles will spew more gas for every time the nozzles open. 

Also if the fuel is under higher than specified pressure in the lines, more diesel will flow through the injector even if the duty cycle is correct. So fuel pump pressure is another thing to check.

Does the fuel pump really have "timing"?  To me that implies it raises and lowers fuel pressure for every injector open/close event.  That doesn't sound right to me. The pressure should be consistent I would think, allowing the injectors to perform the open/close timing.  They are made for this rapid opening and closing to control fuel flow. Seems like a consistent flow would be too hard to control if the pump cycled up and down, in this case 18 times per second at 2200rpms AND the injectors had to syncronize with fuel pump.  I could be wrong.

If this was my problem, I would however first swap the prop as others suggested. A 9 to 8 pitch change is not insignificant, reducing the load considerably.  Then I would use some very strong diesel engine cleaner and inject it directly into the intake (there may be a vacuum line to use on the intake). Run it while injecting cleaner (it will be horribly nasty fumes for a short time), shut it down for an hour to let the cleaner soak into the carbon, then run the engine a hard as you can for at least 15 minutes. That will clean out the carbon.   If no difference, I would look into the injector duty cycle and fuel pressure.   Keep in mind that a computerized control unit controls the duty cycle, not the injectors themselvs. A "black box so to speak has to tell the injectors to open and close

[Salty19]

Some good info here:

http://www.cruisersforum.com/forums/f54/m12-black-smoke-under-load-9365-2.html

This was started on by our own bmiller with the same boat and motor.

Change your prop!

[Craig Weis]

Does the fuel pump really have "timing"? Yep, timed to open as the piston travels up on the compression stroke. Faster piston travel opens sooner. The extra time is needed to inject extra fuel to make extra power. A function of faster crank and piston speed.
And the duration that the injector is opened can be electronic [Bosche] or mechanical [Alfa Romero].

Since the fuel pump is a positive driven gear pump with constant volume delivery the pressure is established at an idle speed and maintained at speeds above idle speed by dumping volume and pressure via recirculation back to the fuel tank. Like on my 12 cylinder Jaguar, the fuel rail was pressurized and controlled by a fuel pressure dump valve.

Some injectors open the same amount and time and deliver the same amount of fuel but open more often when more power is called for. Pulses per second. Think the Oldsmobile Cutlass Cale Quad four. A car that went like a raped ape but lasted like bananas on the counter top. Of course the engine was made by "RONOL, a product of France" as I found out when mine spun a conrod big end bearing and locked up with a full sump of oil.
You can only move incompressible liquids through an orifice at X feet per minute. There is a time when adding more pressure will not inject more fuel unless the 'hole' is made larger. For water it's about 33 fpm.
Speaking of water, I posted this on another site:

Water is the universal solvent. Given enough time water will dissolve your Model A as well as the wife's crystal glass set. Water doesn't burn and becomes a product of combustion and water has tremendous weight yet floats in air. Water flows and bends but can not be compressed and given the latent heat of condensation, stores energy in unbelievable amounts. Water is the best insulator of temperature change and absorbs heat and gives up heat in a constant rate. Water is the chief moderator of temperature. A falling barometer indicates a storm yet the air molecules are pushed so far apart by water the air has less weight and the mercury pushed up a tube by air pressure falls. And yet very dry air indicates high pressure. Air without water. Air without water weighs more than air with water. So why does your model 'A' run better on a cool dampish day? Anyway, way off the reservation here.


If your NOT loosing coolant;
Your making steam. For every 1,000,000 btu's burned about 100 lb of water vapor is condensed within cold tail pipes. That's the part you don't see.

Additionally upon exiting outside the pipe into cooler air you are condensing water vapor and making water and that's the part you do see coming out of the tail pipe.

To help save the black iron [steal] exhaust system from rusting out so fast the manufacture usually drills a weep hole in the muffler to let the water out.

When the wife's Datsun 310 blew a head gasket idling at a rail road crossing on the very day that John Lennon was shot and killed I thought I was driving a Stanley Steamer!

There is about 180,000 btu in one gallon of gasoline and just for poops and grins the world is surrounded in roughly a constant water vapor weighing approximately 700-trillion-billion metric ton of water vapor according to N.A.S.A..

Just because L.A. in California is out of water doesn't mean that the world is drying up since the weight of vapor remains a constant through out our 82,000 foot of atmosphere. It just means L.A. is and has always been a desert. Some places are so wet they wish they were a desert. And antipersonnel munitions do impact and detonate on rain drops.

skip.

[Salty19]

Seems like the fuel timing is or should be the injector solenoid (controlled mechanically or via a black box) instructing the injector to open/close and alter timing based on crankshaft speed/position. It just doesn't make sense to me that a fuel pump raises and lowers fuel pressure.  But as I said, what do I know about diesels! 


Regardless, I think you're overpropped, Allure sail.  Will you let us know what the outcome is?

[CaptRon28]

The Horizon with the 1GM10 Yanmar comes with a 2 blade 12x12 prop. Mathematically, I think I'd be better off with a 13x10 and I may change it one day. I don't think he's overpropped with his 12x9 on the 27. A 12 x8 would be getting into gas engine territory where the motor is usually doing over 4,000 rpm while cruising. With the higher midrange torque of the diesel and the limited rpm range, a 9 or 10 pitch is probably more in order. Unfortunately, the best way to find out is to attempt to get the motor up to redline (3500 rpm ?) in gear. If he can't, then lower the pitch. Remember that diesels MUST have a reasonable load on them to stay healthy. Too much or too little will both cause trouble.

I'd look elsewhere for the problem. A compression test would be the next thing I'd do.

[Allure2sail]

Have the time tomorrow to give it a compression check. I will bring the engine to operating temperature range and check by way of the the glow plug holes, (I have the adaptors). Hoping for 325 psi or above when hot. Both cylinders should be close to that number if healthy. I will let you know the results.
Bruce

[Craig Weis]

Healthy if the cylinder pressure is great enough to fire the fuel [if it runs it is] and with about 8~10 % of each other, me thinks.

skip.