Diesel 101?

[Compass790]

Originally Posted by djousset

To those who encouraged me to spend time with my own engine and manuals before jumping into classes....the universe conspired to give me fire drill training today. Turned the engine over, ready to head out and no water out the exhaust pipe. After a few moments of panic I started to go through all the possible reasons...seacock, raw water strainer, hoses, belt, mixing elbow.... Got to the belt and noticed inconsistent wear on it (anyone seen this?). I replaced the belt and tightened things up and was shocked when it worked. One more box checked on my engine syllabus! Now I need to find out why that happened because there has to be a reason...

Often that fault ( no water) is the impeller so good diagnosis.
The belt wear could be just old age or insufficient belt tension but check the pulleys are inlnine. I.e. put a straight edge across them & check it touches across both faces.
Hope that helps.

[Rob_P]

If the wear is uneven, I'd suggest you get in there and pull the new belt off and hand spin the water pump pulley, the alternator, and anything else the belt powers. Wiggle and pull on them too to see if there's any movement in the pulleys/shafts.

You're feeling for any grinding or binding or slop in the bearings in those accessories. If there isn't any, and the pulley alignment is good (it doesn't have to be perfectly inline but it should be close), I'd say the old belt wasn't tightened properly and had been run that way for awhile at some point.

Just don't overtighten the belt thinking it's better too tight than too loose. It's not and you'll break something expensive. Proper tension is the only tension you should be using.

[dougweibel]

Originally Posted by Stu Jackson

The ONLY class worth taking is one that works on the engine that is in your boat.


Really, not "ideally a Yanmar." Don't even consider or bother spending any time at all on anything else or any other engine.


YOUR engine is the ONLY one you need to learn more about.

Well, I'll disagree. I took the diesel class at The Annapolis School of Seamanship. That class had us hands-on with a good number of diesel engines in the 20 to 100 hp range. One exercise that stuck with me was going around several engines and identifying about 40 different parts. I learned to identify stuff by thinking about what sort of connections it must have to different parts of the engine. With that approach when I forgot or didn't know where something was on my engine I was comfortable figuring it out.

While a class that only had me working with a Yanmar 4JH3E would have served me better initially it would not have served me as well now, as two years later I sold and bought boats and now deal with a Volvo D2-40. Not to mention I used to have a Fischer Panda generator and I now have an Onan.

[tkeithlu]

While you have an offending belt off, run a string around all the pulleys it uses, and eye-ball whether they are in line with each other. Alternators are commonly out of line, because they are mounted loose from the engine and have a variety of attachments. Get everything in line before you install the new belt.

You're getting a diesel 101 course on the forum....

[djousset]

I will definitely check out the alignment, and the condition of the pulleys themselves. water pump">Raw water pump pulley is tucked behind the alternator pulleys, sharing one. (see photo). I will also look into what the proper tension should be. In hindsight I think it may have been too loose. I am learning what needs to be checked each time aboard, each week....each month.... etc.

Thank you all for the help! Ask 4 people and get 5 opinions...and I love that. Different eyes see the same things differently and is an opportunity for growth.

[BigNut]

Just a small update, for those who, like me, consider themselves beginners in engine maintenance. You could do worse than this book:
Marine Diesel Basics by Dennison Berwick. (2017). I have no ties to author. Excellent for beginners, maybe to study before you take a course, if that is your fancy.
It is quite generic, yet delivers the message clearly with great line drawings. Couple this with a few manuals, and your uncle may well be Bob!

[Scubaseas]

Now I need to find out why that happened because there has to be a reason...

Diagnosis in 99% of the battle. From the sounds of it you may need to learn how to adjust valves and learn some basic trouble shooting/ logic tree building and probably not a lot more. You're already way ahead of most people. Do read the Calder book. Definitely read through both service manual and the parts diagrams. Take a mechanics course (not the full blown, just the basics) if there is one at a local vocational school or technical college. Even a basic automotive technology class may be helpful but really Youtube is a Godsend. EVen as a professional mechanic
with over 50 years experience and 42 years running a shop I would still have the guys watch the video sometimes.

[BigNut]

Originally Posted by Scubaseas

Diagnosis in 99% of the battle.

Ya'know Scubaseas, I think I get where you are coming from, and I agree (perhaps, I am too inexperienced to really know) with your statement in response to the specific question.
BUT
For idjits like me, coming to a new field of expertise, this is exactly what leads us astray, I think.
For someone who doesn't even know how to change, say, an impeller, diagnosing a valve issue is simply a bridge too far. That will surely need to be filed away for a while or farmed out to someone who knows what they are doing.

Learning how to adjust valves may be simple for an experienced person (is it, I wouldn't know?), but not for someone at the 101 level?

Personally, I came from a non-mechanical background, but had a lot of basic DIY, and also had taken a small engine course some time in the foggy past.
For me, the issue was separating the wheat from the chaff. Knowing what is important to know. And what is rare and beyond what a beginner should realistically expect of themselves.
For me, even before the ever-importance of "diagnosis", comes "recognition of the normal, the abnormal, and what is in my scope of practice."
Just today, I rerouted an exhaust hose because the piece in place before made it difficult to access the saildrive and impossible to install the breather tube mod. For me, THAT was an achievement, lol! In fact, the biggest challenge was cutting the wire in the hose, my sidecutters balked, so I used a Dremel. I had never done that before, and had never seen anyone else do it either. Is there a better way?
This is the level at which us beginners operate, what can I say? Or perhaps it is just me

[longjonsilver]

Originally Posted by Rob_P

If the wear is uneven, I'd suggest you get in there and pull the new belt off and hand spin the water pump pulley, the alternator, and anything else the belt powers. Wiggle and pull on them too to see if there's any movement in the pulleys/shafts.

You're feeling for any grinding or binding or slop in the bearings in those accessories. If there isn't any, and the pulley alignment is good (it doesn't have to be perfectly inline but it should be close),

Yes! Good advice.

Originally Posted by tkeithlu

While you have an offending belt off, run a string around all the pulleys it uses, and eye-ball whether they are in line with each other.

A string won't do the job very well. Use a straight edge from each point of belt attachment to every other and see if things are in alignment. A pulley could be too far in/out or at an angle.

i am considering buying a boat with a bad engine (Perkins M30), so i might be living this soon, and in preparation i am swapping in a supercharged V6 instead of a 4 banger into my car..... i had to do a lot of custom building of parts for the two belts and get them in alignment.

[BigNut]

Originally Posted by longjonsilver

Use a straight edge from each point of belt attachment to every other and see if things are in alignment. A pulley could be too far in/out or at an angle.

I just read this in the Berwick book.

So, in practice, is it usually the alternator pulley that is out of alignment? How would the crank pulley even get out of kilter?

[BigNut]

Originally Posted by Rob_P

Proper tension is the only tension you should be using.

All well and good, but what IS proper tension? The book I am reading is to put “firm” pressure on the midpoint and read the deflection from a straightedge in the middle of the belt. There is then a table to correlate the distance between the pulleys. It reads differences as small as 1/32” but starts with “firm pressure”.
That just doesn’t compute for me?
How do folks who know do it?

[longjonsilver]

Originally Posted by BigNut

How would the crank pulley even get out of kilter?

The crank pulley is your reference point - everything has to align with it.

[Scubaseas]

For someone who doesn't even know how to change, say, an impeller, diagnosing a valve issue is simply a bridge too far. That will surely need to be filed away for a while or farmed out to someone who knows what they are doing.

Learning how to adjust valves may be simple for an experienced person (is it, I wouldn't know?), but not for someone at the 101 level?

Personally, I came from a non-mechanical background, but had a lot of basic DIY, and also had taken a small engine course some time in the foggy past.
For me, the issue was separating the wheat from the chaff. Knowing what is important to know. And what is rare and beyond what a beginner should realistically expect of themselves.
For me, even before the ever-importance of "diagnosis", comes "recognition of the normal, the abnormal, and what is in my scope of practice."
Just today, I rerouted an exhaust hose because the piece in place before made it difficult to access the saildrive and impossible to install the breather tube mod. For me, THAT was an achievement, lol! In fact, the biggest challenge was cutting the wire in the hose, my sidecutters balked, so I used a Dremel. I had never done that before, and had never seen anyone else do it either. Is there a better way?
This is the level at which us beginners operate, what can I say? Or perhaps it is just me

Valve adjustment is easy on an even number cylinder engine, i.e 2cyl, 4cyl, 6cyl cylinder. And it's a normal maintenance thing. Nothing is broken. or shouldn't be.

For a 4 cylinder take valve cover off. (see youtube -YT) turn crank by hand until first cylinder valves BOTH rock (see YT) and adjust the two loose valves on the last cylinder For a 4 in line engine you get the 1st and 2nd set of valves rocking, go to the 7th and 8th valves and adjust those. The rotate the engine so the #7 and #8 valves are rocking at the same time and adjust #1 and #2 valves. The engine will be at TDC when either cylinder 1 (valves #1 ad #2) rock at the same time. Same for the #4 cylinder when it's valves (#7 & #8) are rocking. It's easier to rotate the engine by hand if the decompression levers are depressed or the glow plugs are out. Do the same process with cylinders #2 and #3 with the exception that the crank will be at BDC when you adjust #2 and #3 cylinders.

This forum is a great resource for fixing stuff. If you can't figure it out and the hive mind here can't it'll break eventually and then you'll know for sure. Or at least you then know enough to call in an "expert". Plus what is available these days on YT is pretty amazing.

Pushing a wrench isn't rocket science. I agree with you it may not be for everyone but you never know until you try. I owned a busy foreign car repair shop for over 40 years. I always encouraged people to take a course just so they knew where everything was, what it was called and hopefully how it sort of worked. You would be surprised how many things got fixed over the phone just by walking the client through the process. Some one held the phone up to the car in Yellowstone and we worked together to get them home. I also have a dive shop that breaks boats on a regilar basis. Most of the time we can diagnose and fix a probem remotely over the phone or via email. While it may be unfamiliar it does not mean it's undoable, Or for a large part anyway.

A lot of times there will be some signs there is a problem. Noise, over heating,leaking, etc. Not always but if it sounds different or isn't quite right you might want to find out why.

Your hose? Whatever works but a good set of diagonal cutting pliers should be in your tool kit. Pull the wire straight out the end of the hose about 1/2" then cut the wire close to the hose. The wire will then go right back into the hose and you won't draw blood next time you go near it from the jagged edge. If Dremel worked, then Dremel worked, hopefully you stuffed a rag into the end of the hose so the grit , rubber and wire dust didn't fall into where it doesn't belong?

[longjonsilver]

Originally Posted by BigNut

All well and good, but what IS proper tension?

This is something you learn from experience. Newer car motors (with a serpentine belt) have a tensioner that gives you (supposedly) the right tension. Older cars have to be adjusted by hand and feel. The newer serpentine belts are vastly better, but it depends on what you have on your motor.

[Scubaseas]

Originally Posted by BigNut

All well and good, but what IS proper tension? The book I am reading is to put “firm” pressure on the midpoint and read the deflection from a straightedge in the middle of the belt. There is then a table to correlate the distance between the pulleys. It reads differences as small as 1/32” but starts with “firm pressure”.
That just doesn’t compute for me?
How do folks who know do it?

Other than years of experience.... There are such a things as a belt tension gauge. Several designs actually.



Firm pressure is maybe 5lbs to 8bs force for a 1/32" deflection. Another way is if you can turn the belt 90* with your two fingers over a long span and it takes about as much twist as opening a screw top beer is also about right. If you can turn it past 90* it;s too loose. Can;t turn it to 90* it's way too tight. Recheck tension after running it for 1/2 hour as some belts will stretch when new.