Perkins 4-108 fuel in exhaust

[neoreundoer]

Here's the facts:
rebuilt engine
New injectors
New pump
runs strong but smokes heavy blue on idle
very little blue smoke from 1000 rpm on up
Good fuel
No restricted exhaust
No restricted air intake
No oil consumption
RAW FUEL IN EXHAUST

I suspect a slight timing issue. What direction do I rotate the pump to advance the timing? (Engine cyl#1 to Bow, pump on port side, mark on pump but not on block) The pump mark is currently centered on the flat area on the block. The old engine had a raised mark on the block. Help please, oil in the water no matter how little is unacceptable and embarrasing.

[Frosty]

Would you know if you had a misfire because thats all I can think of to get raw fuel in the exhaust.

To advance anything is always towards rotation but I dont think it is that.

[neoreundoer]

It runs fine. Idle a 450 RPM.

[gonzo]

I would think it is either the injectors opening at too low pressure or the end of delivery in the pump is not adjusted right

[neoreundoer]

If the end of delivery in the pump is not adjusted right what do I do to correct it?

[Frosty]

Its called phase and calibration and needs a specialist. Take the pump of and take it to one. If you want to do the job right take out the injectors and get the blow off set.

I dont think this is your problem, firstly if you getting combustion and all cylinders are firing why is there fuel in the hot exhaust.

If it was that far out the engine would not run smoothly as you say it does.

Finally how can there be raw fuel in a hot exhaust ,--it would be blowing white smoke like a leaf fire.

[FAST FRED]

Sounds like the rings haven't seated yet.

"runs strong but smokes heavy blue on idle
very little blue smoke from 1000 rpm on up"

Could still be burning oil as the rings seat.

FF

[neoreundoer]

Its called phase and calibration and needs a specialist. Take the pump of and take it to one. If you want to do the job right take out the injectors and get the blow off set.

I dont think this is your problem, firstly if you getting combustion and all cylinders are firing why is there fuel in the hot exhaust.

If it was that far out the engine would not run smoothly as you say it does.

Finally how can there be raw fuel in a hot exhaust ,--it would be blowing white smoke like a leaf fire.
Sorry for late reply, I have been sailing for the last month. The engine continues to be hard starting, (small ether shot to start). On first startup, heavy blue smoke, ( one cylinder clacks loud for about 30 seconds ) I have just installed 4 brand new off the shelf Perkins injectors, and a brand new off the shelf injector pump. I currently have about 400 hrs on engine. The engine is in a sail boat with water exhaust. After warm up, the engine still smokes (more on idle than at 1800 rpm) and the is a little sheen on the surface of the water from the exhaust.

[White Wolf]

My Perkins 4236 does the same and produces a sheen on the water when idling. As you say , it is a problem when you run it at the dock.

I have spoken with several others with older Perkins 4236 and they have similar complaints.

[kapnD]

Although its no consolation, you are not alone! Perkins owners the world over curse in unison. I know, I USED to own one.
Boatdiesel.com forums is a great place to work out your problems, and you can usually find the info you need just by searching the archives and reading. It costs $25 to join, but IMO is well worth it.

[Capchang]

My Perkins 4236 does the same and produces a sheen on the water when idling. As you say , it is a problem when you run it at the dock.

I have spoken with several others with older Perkins 4236 and they have similar complaints.


I own an old 30 ft boat wich Perkins 4236 engine, wich works in Orinoco River .I dont have trouble either temp nor any other motor problem, but when we go against current, wich is sometimes rises 6.7 knots ,sea speed is not more than 3 knots. I made some changes in structure, trying to get less displacement and so far,more speed. Somebody oppined to change propeller picht, other asume that changing gear case ratio will improve speed. The shape is like a lifeboat. :?:

[AlbaDiesels]

This is called "Wet Stacking". Usually the smoke will be white, or blue, and it "smarts" on the eyes. It is usually caused by light running. The temperature of the cooling water may also be too low. Generally, cooling water should be around 70C to 95C. Fuel pump timing is a possibility. If the timing is incorrect then fuel 'misses' the cycle and then condenses in the exhaust. I would advise checking the cooling water temperature, checking the thermostat, and checking the fuel injection timing.

You should get your pump and injectors checked every year really. If you do that you won't really have to worry about them going wrong.

[Capchang]

I though that my boat speed problem was due to, by one side its hull shape,and another side,the propeller. The engine runs well. How can I get more speed in the river.

[CDK]

At idle, injection starts too late, so unburnt fuel leaves the engine. At higher rpm the advance mechanism prevents this.
So the pump needs to be advanced a few degrees against the rotation direction.

[Frosty]

Glow pugs are a necessity in old engines. It will be a devil to start without them needing Etha or other starting methods like a hot air blower.

Heaters /glow plugs can become non operational and need replacement.

This may possibly be why you have one cylinder that smokes. One may be shot.

Some modern diesels have glow pugs that will remain on after the engine has started and may even come on if the engine senses a cold running condition.

Diesels have come a long way since the 4108 and the smoke and bad starting is one reason why.

Im sure the 4108 does not have advance mechanism, so its advance is set, consequently RPM and HP was low with smoky, noisy engines.

[AlbaDiesels]

At idle, injection starts too late, so unburnt fuel leaves the engine. At higher rpm the advance mechanism prevents this.
So the pump needs to be advanced a few degrees against the rotation direction.

Well it's the other way around. Injection timing could be spot on at idle, but as the engine speeds up the IGNITION starts to retard. This is because of the pretty much constant injection lag and ignition delay, and the fact that as engine speed increases, the time available for combustion decreases, so it appears that the point of injection is occurring later (retarding), when in fact, it's always at a constant crank angle. In effect, because of the constant delays due to injection lag and ignition lag, as speed increases the fuel ignition and combustion occurs later and later in the cycle than it should.

The advance mechanism compensates for this by advancing the timing.

Engines with pumps not fitted with an advance mechanism will generally have the timing advanced at idle, and the timing optimised for a particular speed/load. This way the timing 'naturally' retards until it's at the optimum point for the speed, whether thats 1500/1800/3600 rpm for a generator, or for cruising speed or a set speed for a CP prop, or whatever.

If the pump is fitted with an advance mechanism, then failure would cause smoking, excessive fuel consumption and loss of power.

Running the engine at idle (low loads) for periods of time can cause the problem of fuel in the exhaust (wet stacking), partly because the engine cools down. I see this all the time in engines such as Kelvins.

[CDK]

Well it's the other way around. Injection timing could be spot on at idle, but as the engine speeds up the IGNITION starts to retard. This is because of the pretty much constant injection lag and ignition delay, and the fact that as engine speed increases, the time available for combustion decreases, so it appears that the point of injection is occurring later (retarding), when in fact, it's always at a constant crank angle. In effect, because of the constant delays due to injection lag and ignition lag, as speed increases the fuel ignition and combustion occurs later and later in the cycle than it should.



I was not lecturing about diesel engines in general, just finding an explanation for the behavior of this particular one.
Believe it or not, I know quite well how engines work and so do you.

When responding to a question we have to rely on the data supplied, unless that is obviously wrong. If a rebuilt engine with only 400 hours keeps expelling unburnt fuel at idle only, the injection and hence the combustion starts too late. At higher rpm an advance mechanism will improve that. With an engine idling at only 450 rpm, the timing -when set correctly- will always be fairly late.

There are many other possible causes like a burnt or damaged exhaust valve, broken rings or an injector that doesn't close, but then the question should have started with a different engine story, like just rebuilt or a very worn, neglected one.