Help me trouble shoot my engine!

[weinie]

Help me trouble shoot my engine! Update pg 5

I have a universal m18 diesel in my 1987 Catalina. As the hour meter is shot, I don't know how many hours have been put on it in its lifetime. I have owned this boat for two years now and have completed redone almost every item on the boat except the engine itself (yet!)

The engine starts okay and there are no major smoke issues noticeable at the exhaust, though I seem to get a buildup of black gunk on the transom above the exhaust port.
I need to keep the idle speed set at over 1000rpm to keep it stalling while in gear at minimum throttle, especially while docking.
The maximum rpm in neutral is about 2800-2900 rpm. Should be 3200 according to the manual.
I'm getting a "gentle breeze" from the crankcase breather tube and have since routed the end of it from its location clipped next to the air intake so that now it is piped directly into it the intake itself. The cabin was also filling with fumes before I did this.
I also get some vibrations at lower rpms when not under load which may or not be motor mount related.
I don't know if the engine has ever been overhauled before.

I've never done any "major" engine work before, but I wouldn't mind learning how to do it! (I have Nigel Calder's book next to me now). My biggest enemy here is physical access to the engine. It's almost all from the front and working from the side is possible too, but tight. I'm pretty confident the engine will get me through the season, but the perfectionist in me wants it to run at its best!

I'm thinking I should run a compression test at this point.
What do you guys think?

 

[Stu Jackson]

Actually, it sounds quite good. What makes you think a compression test is necessary. The rpms being "out" should not be much of a concern, since they run off the tach which could be out of calibration at the tachometer. You can easily reset the minimum rpms right at the engine. See where the throttle cable connects to the engine? Right above that should be two screws, probably locked with wire. Fiddle around and you'll easily see which one is the stop for the minimum throttle. I have this same exact issue, could be from the cable expanding over the years. I have yet to do it, and just keep the engine at 1000 rpm when I throttle down. You are a "regular" here and i'll bet if you read all the posts during any given two week period, there will be all sorts of Universal engine questions. Read regularly, learn lots! I know, I know, some people have real lives... Good luck.

 

[kloudie1]

Check/correct all the easy stuff first, Weinie.. exhaust elbow blockage will do what you are describing. Bad fuel, plugged fuel tank pick-up inside the tank, very small air leaks in the lift pump lines. a lazy lift pump.. bad tachometer.. plugged filters..I would check all that stuff before starting to pull injectors for a compression test. It may well be that it needs an overhaul, but I wouldn't assume that right off.. Happy Hunting !

 

[weinie]

Wow that was quick. You guys must also have no wind today!

The accuracy of the tach was confirmed a few months ago with a digital "laser" tach from harbor freight. I also replaced my muffler last month and there was no major carbon buildup in the hose that concerned me. Removing the exhaust manifold and elbow looks like a project if those bolts are rusted good, and accessing the aft end of the engine is a bitch and a half. The elbow itself looks good... perhaps it was replaced by a previous owner, though I have read here that that a symptom of a clogged exhaust is black smoke and I'm not seeing alot of it here.

Fuel is probably is not the cleanest. I rely on the mesh filter in my lift pump for my primary filter as I don't have a "real" primary w/ a water separtor. (I did buy a racor from CD but I can't seem to find any convenient place to mount it). Anyway, I changed the filters when the boat was put in the water in April and the the engine performed as above. Im no expert, but I would think that if there was air is leaking into the fuel lines or the lift pump was finicky or the fuel was fouled, the engine rpms would bounce around rather than remain steady.

I figured a compression test should be easy enough to do (never done one before) and would confirm the cause of the blowby that I'm feeling from the breather tube. If compression is indeed lousy, I have read that adding drops of oil to the cylinders would indicate whether gases were leaking past the valves or piston rings.

 

[Stu Jackson]

That blowby you are mentioning is a built-in device in the engine & is not a problem.

I rely on the mesh filter in my lift pump for my primary filter as I don't have a "real" primary w/ a water separtor. (I did buy a racor from CD but I can't seem to find any convenient place to mount it).

Don't do that, OR check that small filter very often. You really should find a place to install the primary, and it should go before the lift pump.

You might be interested in these which are mostly for M25 engines but are pretty applicable to yours

http://c34.org/bbs/index.php/topic,5078.0.html

http://www.c34.org/wiki/index.php?title=Diesel_Engine

All the best,

Stu

 

[Stu Jackson]

More engine stuff

You might also be interested in this:

http://www.ericsonyachts.org/infoexchange/showthread.php?10244-M25XP-Air-Intake-woes

One of literally dozens of posts by Maine Sail on this subject.

 

[kloudie1]

OK.. then you've covered lots of the easy stuff.. so ya might be correct in going for a compression check.. usually a low compression engine would consume a good bit of crankcase oil (ya didn't mention if it was ) and it might be harder to start.. Messing with the injectors on an old engine (to get compression check access) is usually a lot more difficult than it would seem to be. A governor reset might be in order.. to allow the engine to get to max RPM in neutral .. and as Stu noted, set up the idle stop a little. again, Happy hunting..

 

[stevec22206]

Weinie, I just completed the installation of the racor filter Thursday. We have the 87' model. We have a electronic fuel pump mounted inside the engine compartment on the left side. I mounted the racor just aft of the pump, just above the opening for the quarterberth access panel. Replaced all the hoses, new clamps, removed the pickup tube from the tank and found the screen sock coated with snot from the bottom of the tank. Removed the screen sock and discarded it. Also cleaned the fuel pump filter, ours has a stone filter. Will try to take some pics when I back at the boat.
Steve

 

[weinie]

Weinie, I just completed the installation of the racor filter Thursday. We have the 87' model. We have a electronic fuel pump mounted inside the engine compartment on the left side. I mounted the racor just aft of the pump, just above the opening for the quarterberth access panel. Replaced all the hoses, new clamps, removed the pickup tube from the tank and found the screen sock coated with snot from the bottom of the tank. Removed the screen sock and discarded it. Also cleaned the fuel pump filter, ours has a stone filter. Will try to take some pics when I back at the boat.
Steve

Hey Steve,
I was going to mount the unit there but I was concerned about blocking off access to the engine. That and the filter was screwed on so tight that I was concerned that twisting it off would crack the thin fiberglass that the top of the unit would be bolted to there. I thought of making a backing plate, but there is still not much room above that wood access door for one.

I will definitely check out that screen "sock" asap. I didnt know there was one there!
ok ... stupid question... How do I get to it?!?!?
btw, 1987 here too.

 

[JK_Boston_Catalina310]

I have one other easy item to check. The air filter. A clogged air filter will also give u black exhaust. If you still have the metal mesh, consider upgrading to a K&N. Should cost about $50 and can easily be cleaned and recharged.

Good luck

 

[stevec22206]

As part of the racor installation I replaced all the fuel hoses. The pickup tube is attached to the fuel shut off valve on the fuel tank. Disconnect the hose at the valve fitting. I unscrewed the valve from the elbow fitting that threads into the tank and then unscrewed it (the elbow) from the tank. The pickup tube is attached to the elbow fitting. Ours has a solid tube about 8-10" long with a short piece of fuel hose attached at the bottom. The screen sock was fitted to the end of the hose. Removed it from the end of the hose and cleaned the hose/tube combination, then reinstalled it. As far as the racor install goes I installed a 1" wood backing block between the fiberglass and filter. It provides a little offset and a better foundation for the filter. As noted on a previous thread I disassembled the filter kit and lubed the gaskets for the bowl and filter before installing it. Hand tightened. I had to put the racor into a vice to remove the filter and bowl. Would never have gotten it off later if installed out of the box. The filter itself hangs just at the upper level of the access panel frame. If necessary, I could easily remove the filter to gain total access to that side of the engine.

Steve

 

[Stu Jackson]

FWIW, you only need to hand tighten the filters. They may come locked up from the factory. Do NOT use a strap wrench to tighten them.

 

[weinie]

Decided to dive into my fuel tank today...and lo and behold... there was the crudded up screen at the bottom of the pickup tube. I pulled it out with some pliers and re-installed the tube. Glad I did it, however, no improvement as far the above complaints.

 

[anchorclanker]

A diesel in a sailboat sees so little use, and from what im reading almost zero maintenance, its amazing so many run so well, or at all. However, they are generally very robust engines that could, under proper care, run 10's of thousands of hours.

While a compression test would tell you its current state, it will not tell you why its in that state. Rings will get all gunked up from poor running and lack of regular oil changes. And yes, gunked is a word. If you dont like gunk, try carbon mixed with grease. In any case it makes the rings stick and they dont work properly. The cylinders can become carbon polished, also leading to low compression. Unless the engine wont start or run, a compression test may not tell you much.

I would begin with a thorough tune up. I would start by putting a quart of MMO (marvel mystery oil) into the crankcase for every 4 quarts capacity. Find some diesel purge, tap it into the fuel supply, and run it through the fuel system (fast idle only, not driving) while the MMO works on cleaning the insides. When the purge runs out, shut it down and drain the oil.

Next remove and clean the injectors. Service the cooling system. Clean the fuel tank. Check injection timing by reading the service manual. Change all the fuel filters, and listen to the guys who tell you you need a good primary filter with a water trap. Once all this is done, when you put in new oil (and new oil filter), replace one quart of oil with MMO. Now take the motor out and run it HARD. Full throttle, wide open. I would plan on running it hard for several hours at a minimum. While your running it, slow it down or stop it as needed to check oil, see how its idling, make any adjustments needed, and go back to running it.

If the motor has led a lazy neglected life, it could take several or many hours of hard running to blow the gunk out of the rings and burn the carbon off the cylinders. Only after all that would I bother with a compression test. You may well find the engine is now running like new, and with care may run well for another 20 years.

 

[weinie]

Anchorclanker,

Will clogged injectors cause the blowby or the difficulty I have stalling at speeds below 1000rpms? Then there is the belief that injectors should only be removed by "the pros".

I know some people swear by MMO and I suppose it won't harm anything at the next oil change. I would imagine if the rings and valves were carbonized as you say, there could be added friction which would explain the both the stalling at low speeds and the lack of top end speed.

Also, to the posters above, the air filter is new and I do not have any significant oil loss, though it does turn dark rather quickly.

Of course, I don't know squat about engines, so this is all an attempt on my part to get other people posting their ideas!

 

[anchorclanker]

Anchorclanker,

Will clogged injectors cause the blowby or the difficulty I have stalling at speeds below 1000rpms? Then there is the belief that injectors should only be removed by "the pros".

I would imagine if the rings and valves were carbonized as you say, there could be added friction which would explain the both the stalling at low speeds and the lack of top end speed.

Of course, I don't know squat about engines, so this is all an attempt on my part to get other people posting their ideas!

These engines really are not very complex, and a good service manual, as well as a good book on basic mechanics will go a long ways toward helping someone figure out minor problems. You certainly dont need to have knowledge of complete engine overhaul, just some basic ideas of how they run and how to make basic adjustments. In many cases the guy who would come out to fix your engine may not know any more than you, and occasionally less.

No, the injectors will not cause blow by. Blow by is from the crankcase, its the high pressure combustion gasses that are escaping past the piston rings. The pressure is being generated after the fuel exploded in the combustion chamber, at the top side of the piston. Those gasses are to push the piston and in turn, turn the crank. There shouldn't be much if any blowing into the crankcase or out the oil cap.

As to the friction, there would be much more if the rings were holding pressure. The problem your seeing is the energy to spin the engine is being lost past the rings, rather than doing all the work as intended. The pumping losses as well as the propeller drag are what are making it quit. There simply isnt enough power available to overcome the losses. Increasing the compression by fixing the rings and cylinders will restore the designed power back and the engine would run properly again.

Diesel generators in RV's have the same troubles. Rather than run at maximum power, they often loaf along producing only minimal electrical power to run low wattage appliances. Unlike a boat prop, they may be governed to run at 1800 or 3600 rpm constantly, but they arent doing enough work. Just like these sailboat engines, the cylinders become glazed, the rings begin to foul with unburned fuel and coked up oil, and compression begins falling off, the engine begins smoking and you start noticing blowby at the oil fill cap. Only by running them HARD, at full rated load, is there any hope of them healing themselves, and then only if it hasnt progressed too far. And your boat engine is likely in the same boat, no pun intended.

If you cant get it to come back your then going to have to dig into it. If you remove the head, youll be able to measure the cylinder wear. If none exists, which would be my guess, you could likely get by with a simple re-hone on the cylinder/s to break the glaze, put in new rings and run it another lifetime. And if there really in no cylinder wear or piston wear, you could re-use the rings (after thorough cleaning/decarbonizing. But I would run the snot out of it as long as makes reasonable sense before I tore into it. Run it for two days real hard. If its still the same after that, youll have to tear into it. If the engine is running better and has less blow by after that time, even if its still not perfect, keep running it hard a while longer. If the oil goes black right away, change it. Youll need good fresh oil to scrub the internals clean. The MMO will also help, its highly detergent.

 

[anchorclanker]

Oh. Taking the injectors out isnt rocket science either. Read the manual, use the right tools, and be careful. You can disassemble them and clean them in mineral spirits, again being careful and reading the manual, making sure to re-assemble them correctly. If you have them in your hand, most automotive diesel garages will test them for you for spray pattern and break pressure, and leakage. Years ago it was considered part of tuning up a diesel to clean injectors. Checking injection timing is not generally difficult either. Most any special tools you might need can usually be made quite easily if you use your head.

 

[Richard19068]

Is the stalling a fairly new symptom?

have you checked to see that nothing is wrapped around the prop or shaft anywhere?

Just a thought that I haven't seen addressed so far in this thread.

 

[weinie]

Is the stalling a fairly new symptom?

have you checked to see that nothing is wrapped around the prop or shaft anywhere?

Just a thought that I haven't seen addressed so far in this thread.

When I had the engine idle speed set at a more normal 8-900 rpm range, the boat would often stall when maneuvering back to the dock with minimum throttle; the worst possible time! And other than the engine coming up 400 rpms short of the manufacturer's spec for maximum rpm, it performs ok otherwise (save a bit of vibration) and gets the boat up to hull speed even against a brisk wind.

Also, the hull was scraped to the gel coat over the winter and new prop shaft, coupling, and cutlass bearings were installed too. As I had the same problems with the engine last year before this work was performed, it is clear that there is no unusual, external load that would cause any issue.

 

[weinie]

As to the friction, there would be much more if the rings were holding pressure. The problem your seeing is the energy to spin the engine is being lost past the rings, rather than doing all the work as intended. The pumping losses as well as the propeller drag are what are making it quit. There simply isnt enough power available to overcome the losses. Increasing the compression by fixing the rings and cylinders will restore the designed power back and the engine would run properly again.

I think you confirmed it for me. I can't think of any other reason why the engine would have the symptoms it does! I would think the compression test would have indeed verified what you have just said.

It looks like a closer examination of the piston rings is in the near future, probably at the end of this season. At that point, I suppose a full rebuild might as well be undertaken.

That's why I think, at this point, it might be wasting time to mess with the injectors and the rest of the fuel system, lubrication, and coolant. I'm not saying cleaning the injectors and fuel isn't necessary, I'm saying that it's probably not the cause of the problems I am having and would all eventually be addressed with a rebuild.

... or is my thinking overly fatalistic?