Perkins 4-108 Smoking enigma

[avazquez]

I have a Perkins 4-108 on my Beneteau 456. The engine was overhauled by the previous owner. New pistons, liners, rebuilt, fuel pump etc etc.

The engine smokes upon startup with gray smoke. When in gear and running at crusing speed the smoke goes away and the engine runs fine. The temperature barely reaches 180F It usually stays aroung 160 to 170F during cruising which is around 2200 to 2400 RPM. As soon as you put the engine in neutral and it goes to lower rpms it begins to smoke gray again. Actually if you accelerate in neutral it still smokes but if it is in gear it stops smoking as soon as you accelerate.

I already took the injectors to have them checked and cleaned...reinstalled them and no change.

Replaced all diesel fuel lines and filters with a new Racor.

Cleaned fuel tank and filled it with fresh clean diesel.

Checked the timing of the fuel pump.

Still smoking

Any suggestions would be apreciated

[CSY Man]

Hmm, gray smoke?

It is either blue, (oil), black (Un-burned fuel) or white (water or coolant)

Hopefully not a combo...?

Some smoke after start-up is normal in any diesel however. Same with acceleration.

[Jesse Holden]

I'm wondering if the rings are seated yet? How many hours on the rebuild?

[Alan Wheeler]

Jesse has asked a very good question. Of course, it's a little hard to answer you problem without knowing just how bad the smoke is. These engines do smoke a little and I imagine the engine is just fine. When you start the engine, make sure you get it into gear ASAP and warm it up under load. Do not allow it to idle out of gear to warm up.

[avazquez]

It has maybe 20 hours.

It runs fine under load.

One doubt I have with the timing of the pump:....In the manual it says that the marking with the letter "A" (or the K ) corresponds with static timing, 18 degrees BTDC.

When we placed the engine in top dead center......the marking in the pump corresponded to the letter "A" or K. Could it be that the timing in the fuel pump s incorrect????

[avazquez]

Also....I noticed that it takes a while for the engine to reach 170F. When the load is removed from the engine it looses temperature kind of fast and drops to about 145-155F.

Could it be a thermostat issue???

[avazquez]

Also I would say the smoke is more white in color......

[Maddog]

Originally Posted by avazquez

Also....I noticed that it takes a while for the engine to reach 170F. When the load is removed from the engine it looses temperature kind of fast and drops to about 145-155F.

Could it be a thermostat issue???

Wait a minuet. We are concerned about a perkins running cool? I would be more worried about the gauge. Have you checked that?

I checked the perkins manual, Section "D" Fault diagnosis and it does list blue/white exhaust can be caused by cool running.

My question is, "Is this a problem?"

[avazquez]

I don't know?

I just purchased the boat four months ago and I got concerned about the excesive smoke.

Then the question would be, what is the normal operating temperature for this engine at idle?

I suspect there might be something goin on with the thermostat since it takes so long to warm up under load and then it drops temperature rapidly.

Should I replace the thermostat? If so....are there any options in terms of temperature or is there only one type of thermostat for these engines???

Thanks

[CSY Man]

The thermostat is a b1tch to replace on my 4-108.
Perhaps easier on other models: Low Line, New or whatever they call the various versions.

Try to change the gauge and sender/wire first.

I did that 5 years ago, used these people:

WEMA USA, Inc. Home Page - Boat fuel, water and holding tank level sensors and related instruments

[Maddog]

My Perkins runs nicely at 180 warmed up, at idle and under load. The manual says it should start to open at 175-182 and that sounds about right. Get a thermostat This is the easiest and simplesest changes to make. Then you know for sure what you got. I would do this and change the coolant at the same time. Then you know where you are starting from.

[Maddog]

Originally Posted by CSY Man

The thermostat is a b1tch to replace on my 4-108.
Perhaps easier on other models: Low Line, New or whatever they call the various versions.

Try to change the gauge and sender/wire first.

I did that 5 years ago, used these people:

WEMA USA, Inc. Home Page - Boat fuel, water and holding tank level sensors and related instruments

CSY - That looks like good stuff. I am going to redo all my engine gauges in the near future and was going to go with the Teleflex Heavy Duty line. Any thoughts?

[CSY Man]

Get a thermostat This is the easiest and simplesest changes to make

Hmm, ya must have a different model 108 than me:

I seem to remember having to remove the exhaust manifold and the coolant tank to get to the thermostat.

I changed it anyway and saw no difference in working or max temprature.

Mine run about 185 degrees and is stable under all conditions except when I cruise above 2500 RPM or so, then it slowly but surely climbs into the red.

[CSY Man]

CSY - That looks like good stuff. I am going to redo all my engine gauges in the near future and was going to go with the Teleflex Heavy Duty line. Any thoughts?__________________

Don't know anything about Teleflex, probably good stuff however.

The reason I went with WEMA is that I know the owner of the company and get my stuff for half price..

Good products however, I have 6 WEMA gauges on the boat and they never gave me a problem.

[hellosailor]

A note about thermostats, thermo senders, and other tiny dictators and terrorists.

If you are going to replace any of them--test the new one. The thermo sender is easy to test in situ on the engine. Most of them are standard termistors that you can test with an ohm meter. They will read somewhere between 0-40 ohms when red hot, 200-240 ohms when the engine is cold, and someplace in between at normal temperatures. Anything close is usually good, when they go wrong they tend to go VERY wrong.
You can also remove the sender, place it in a pot on the range with a kitchen thermometer, and check the temperature versus resistance there. You unplug the sender wire, attach an ohmmeter where it was connected, and then measure the resistance to the block or ground or exterior of the sender.
Similarly, even a new thermostat should be checked in a pot of water, sometimes they are DOA. They usually work when a tiny hydraulic cylinder filled with thermal wax expands/contracts to power the whole works, and that wax can leak, or be mis-filled when new.

So, first check the little critters that love to drive humans crazy, and only THEN assume the temp readings are right. ~140F is right for a raw water cooled engine, ~180F for a closed-water (radiator) engine. When the engine is working right, and the cooling system working right, tmeperature should not change much, if at all, from idle to load.

I think we've had some other threads about how you really need to check the whole cooling system, from intake to exhaust, for all the "I shoulda seen that" things that can cause problems like this. Hosings, fittings, filters, intake clogs, lost impeller blades...