Two-cylinder diesel: one hot, one cold!

[NevisDog]

Photo from starboard side of engine:

[NevisDog]

Geeze it's taken me an hour to upload photo!

The box along the top of the engine on the far side (right at the back) is where the exhaust gases enter a water-cooled box before exiting the exhaust downpipe at left. Raw cooling water enters from the water pump at bottom right foreground (just out of shot) through the flexi-pipe in foreground; the Tee added centre foreground allows raw water to bypass and Tee into the flow that exits top of exhaust cooling box at far right and mixes with exhaust gases at far left of photo. The red lever in foreground, bottom left, now allows me to restrict raw water flow entering engine block at bottom foreground. I can open that right up and if necessary I may have to close off the bypass.

The paper towel bottom right is to collect drips of diesel from the fuel pump on the front of the engine that drips a little, if that may be relevant?

The forward half of that water-cooled exhaust box is very hot (too hot to touch) at idle, while the aft half is cool to touch. I guess that indicates something more serious than raw water blockage.

[Cadence]

Originally Posted by NevisDog

I thought I was sooo clever, diverting half of the raw water cooling straight to the exhaust to increase running temperature, from a low blood-heat (barely warm) up to a more acceptable 80C (180F). Though this Lombardini AD290 twin cylinder has always been a slow starter, requiring six or eight attempts of the starter motor, it otherwise seems to run smoothly enough (at what seems a rather high idle) with enough power to drive us at seven knots under way, so it came as a shock this morning to discover that the fwd cylinder at idle is too hot to touch, while the rear cylinder remains almost cool.

I guess there are plenty of possible causes: blockage in cooling water to/from fwd cylinder jacket; no fuel to aft injector; lack of compression on aft cylinder; could even be the aft decompression lever is engaged... I wouldn't know. No idea where to start looking. Would Nigel Calder's book on diesel engines cover this sort of troubleshooting? Or is it possible that my deliberately reduced flow of raw water through the engine will never balance out the cooling?

Maybe I missed it? Did you reverse your alteration? If not a good place to start.

[NevisDog]

Originally Posted by Cadence

Maybe I missed it? Did you reverse your alteration? If not a good place to start.

Unfortunately my "brilliant" idea to increase running temperature above 'barely even warm' was the only thing that highlighted there is a problem - possibly a major problem. Once I identify the route cause(s) I can revert to full-flow cooling again if necessary.

[Cadence]

Originally Posted by NevisDog

Unfortunately my "brilliant" idea to increase running temperature above 'barely even warm' was the only thing that highlighted there is a problem - possibly a major problem. Once I identify the route cause(s) I can revert to full-flow cooling again if necessary.

Maybe it highlighted a problem. I would prefer to troubleshoot a problem under factory spec.. JMHO best of luck.

[NevisDog]

Just an update -
1. those decompression levers have no effect on either cylinder; presumably they are not even connected on engines without hand-crank capability fitted?
2. opening/increasing the flow of raw water to the block helps to reduce temperature of the exhaust box on top of the engine but fails to reduce temperature of forward upper cylinder jacket, which remains too hot to touch (while aft one continues fairly cool). Makes me suspect blockage??

Later today/tomorrow I'll have time to open up the water jacket covers and will post what I find; I just can't believe it can run so nicely on a single cylinder - little bit of white smoke but nothing that would concern me.

[Wulf]

Originally Posted by tkeithlu

The back woods farm mechanic who taught me diesel basics tested them by clamping one in a vise, filling it with WD-40, and then hitting it on the top with a hammer. You got a fog out the bottom or you didn't. Crude but effective.

Just a word of caution on testing injectors...although minuscule in amount the fuel coming out of the tip is at high pressure and velocity. It can easily penetrate skin and if that happens consequences are dire and may even result in death. Loss of limb not uncommon. I knew a machinist who passed away from resultant complications just 6 months after receiving a shot of hydraulic oil in his hand even though he immediately sought medical attention.
Keep fingers, hands etc clear at all times.
It’s easy to have a lapse or unknowingly place a finger over a pressure port thinking it’s not functioning, then....surprise! Life changing experience.

[a64pilot]

OK return cooling to factory spec.
The manufacturers had no emissions to meet etc and no ulterior motives not to make the cooling correct, in fact I’d bet they knew what they were doing
You are almost certainly running on one cylinder, the high lumpy idle is one clue, the hard start another, but being cold is a dead giveaway.
It could be an injector or the injection pump, or it could be a busted piston etc.
Easiest way to confirm a dead cylinder is to loosen the “B” nut to the injector about a half turn, a little fuel will leak out each compression stroke, put a rag around it, it’s not much fuel, but with the line loosened there will be no fuel being injected. I suspect loosening one will do nothing, and loosening the other will cause the engine to die.
Loosen one at a time of course.

Things like cylinders and heads etc expand and contract based on temperature so if an engine has spent years and thousands of hours running at X temp, you don’t want to change that temp, you want to keep it running the same temp it always has.

Don’t test your own injectors unless you know what your doing, too cheap and easy to have someone do it and you really can’t test an injector as pressures when it opens and closes are important, and you can’t tell that smacking one with a hammer.

[NevisDog]

Originally Posted by a64pilot

OK return cooling to factory spec. They manufacturers had no emissions to meet etc and no ulterior motives not to make the cooling correct, in fact I’d bet they knew what they were doing
You are almost certainly running on one cylinder, the high lumpy idle is one clue, the hard start another, but being cold is a dead giveaway......

All great information. The brilliant (er, stupid) modification was intended to compensate for not having any thermostat (nor anywhere one could be fitted). I think lack of thermostat is just what was done on all the older-generation small engines I've come up against, not something that was intended to improve performance. This one runs stone cold, normally - not something I really want on any engine but I take the point about precipitating salt at high temps.

Inside the water spaces is a precipitous growth of tiny barnacles, so next thing is to clear out the waterways, regardless of what's causing this particular issue. I have a small electric pump somewhere I can use to run vinegar or some proprietary cleaner through for next 24 hours or so, then look inside again. Not a pretty site at the moment; this amount of muck may block up even more when it is loosened, so I'm not expecting this part to be easy.

Next I'll fire her up again and crack the fuel pipe to the cooler cylinder to see if that makes no difference (then do same with hot cylinder to see if it dies completely). You've all bin a great help.

[jimbunyard]

Couldn't find much information on the Arona AD290, but some assumptions can be made from your picture.

See below for reference.

If 1 is the raw water pump outlet; it should be plumbed directly to 2, the water manifold that feeds the engine cooling water.

I'm assuming that the hose with the tee that you have running from the r/water pump loops around and feeds into the 90 el at 2, the water manifold?

If so, the water is going to take the path of least resistance and go mostly right out the exhaust elbow via the hose 3. The pressure from the r/water pump will also try and back feed through the exhaust manifold, cutting off any coolant flow through the engine.

There is probably a t'stat somewhere, under the exhaust manifold is a likely place (as in you have to remove the manifold to get to it).

You could put the valve you have now between 1 and 2, with no tee or hoses anywhere else, and control the flow of water through the engine that way, though, as previously advised, with a raw water cooled engine you want to stay below 160 F.

The 90 elbow (4) on the front end of the exhaust manifold should be hooked directly to the exhaust elbow (5) on the opposite end, though if you wanted to bypass a certain amount of water overboard to reduce flow through the exhaust, this is the traditional place to do it, after the water has done its job cooling the engine...

And finally, certainly a fuel leak can cause hard starting, among other things. Best to get that sorted out, though hard or prolonged starting is, often as not, a case of slow starting (rotational) speed, usually because of bad connections or slightly flat batteries...

[NevisDog]

Originally Posted by jimbunyard

... ...
If 1 is the raw water pump outlet; it should be plumbed directly to 2, the water manifold that feeds the engine cooling water.
I'm assuming that the hose with the tee that you have running from the r/water pump loops around and feeds into the 90 el at 2, the water manifold?

Yes, that loop has always been there.

If so, the water is going to take the path of least resistance and go mostly right out the exhaust elbow via the hose 3.

Yes, that set-up allowed me to increase engine water temp from cool (not registering on temp gauge) to 80C, by setting red-handle ball vv to approx half-closed.

The pressure from the r/water pump will also try and back feed through the manifold, cutting off any coolant flow through the engine.

I estimate half the flow goes each way with vv fully open, closing vv half-waay got me the temp I wanted.

There is probably a t'stat somewhere, under the exhaust manifold is a likely place (as in you have to remove the manifold to get to it).

That raw-water heat-exchange box around the exhaust is the exhaust manifold. It has two entry points for raw water, one from each cylinder jacket, with nowhere in between that a single thermostat could divert flow. Pretty sure there's no thermostat.

You could put the valve you have now between 1 and 2, with no tee or hoses anywhere else, and control the flow of water through the engine that way, though, as previously advised, with a raw water cooled engine you want to stay below 160 F.

I wanted to maintain full flow of raw water to exhaust - don't want to restrict total flow from pump.

The 90 elbow (4) on the front end of the exhaust manifold should be hooked directly to the exhaust elbow (5) on the opposite end, though if you wanted to bypass a certain amount of water overboard to reduce flow through the exhaust, this is the traditional place to do it, after the water has done its job cooling the engine...

Yes, water exits from front end of manifold through hose to exhaust at opposite end - can't think of any reason to reduce raw water to exhaust.

And finally, certainly a fuel leak can cause hard starting, among other things. Best to get that sorted out, though hard or prolonged starting is, often as not, a case of slow starting (rotational) speed, usually because of bad connections or slightly flat batteries...

Yes, I attributed hard starting to fuel leak. Start battery is good.

Yes, must try to sort out that fuel drip, but it wasn't a priority, but noticing one hot and one cold cylinder has suddenly made me sit up and do something. It's gradually become more noticeable over past three starts, if that provides any clues. Started off a little bit of temperature difference, next time the difference was enough to get me wondering, but now it's extreme and I have to find out why.

[Wotname]

Originally Posted by NevisDog

Yes, must try to sort out that fuel drip, but it wasn't a priority, but noticing one hot and one cold cylinder has suddenly made me sit up and do something. It's gradually become more noticeable over past three starts, if that provides any clues. Started off a little bit of temperature difference, next time the difference was enough to get me wondering, but now it's extreme and I have to find out why.

Possibly a new fault developing and nothing to do your "cooling /heating mod".

Even so, as others have suggested, it is better (easier?) to troubleshoot with the mod removed. Reinstate it once all other issues are sorted or at least fully understood - fuel leak, temperature difference, slow starting.

[Wotname]

Originally Posted by GILow

Strangely similar to descaling a coffee machine.

This had me scratching my head for awhile until I twigged you referring to Adelaide coffee machines...

[NevisDog]

The 'raw water bypass' mod: I can see how the reduced flow pressure through the water jackets would likely exacerbate any blockage, lower flow allowing easier crud buildup and allowing things to get worse more rapidly, assuming the main cause is the build-up of crap in there. Now I know high temperatures and raw water cooling are incompatible, I'll likely remove the mod entirely. Engine is now filled with white vinegar; tomorrow I'll pump it through for an hour or two, look inside again and clean what I can, then see if temperature difference is any less. If not then on to Plan B: see how it runs with each fuel line cracked open. Final part of job will be overhaul leaking fuel pump. Oh well, at least I know where we're headed now. Why am I destined always to own engines from previous centuries?

[jimbunyard]

Yes, that loop has always been there.

It is likely wrong and added later by someone who didn't understand the flow of water through the engine.


If so, the water is going to take the path of least resistance and go mostly right out the exhaust elbow via the hose 3.

Yes, that set-up allowed me to increase engine water temp from cool (not registering on temp gauge) to 80C, by setting red-handle ball vv to approx half-closed.

Which, as we all seem to agree is about 20F too hot for a raw water cooled engine, and may be much more, depending on where you're measuring the temperature from...


The pressure from the r/water pump will also try and back feed through the manifold, cutting off any coolant flow through the engine.

I estimate half the flow goes each way with vv fully open, closing vv half-way got me the temp I wanted.

No water should go back into the exhaust manifold jacket outlet; putting pressure into the outlet will impede (or stop) flow through the engine.


There is probably a t'stat somewhere, under the exhaust manifold is a likely place (as in you have to remove the manifold to get to it).

That raw-water heat-exchange box around the exhaust is the exhaust manifold. It has two entry points for raw water, one from each cylinder jacket, with nowhere in between that a single thermostat could divert flow. Pretty sure there's no thermostat.

Without a drawing or picture of the manifold or engine, we're both just speculating. Most engines have regulatory t'stats; on marine engines, the junction between the water cooled exhaust manifold and the head is a common place for them. There could be one or two or none.


You could put the valve you have now between 1 and 2, with no tee or hoses anywhere else, and control the flow of water through the engine that way, though, as previously advised, with a raw water cooled engine you want to stay below 160 F.

I wanted to maintain full flow of raw water to exhaust - don't want to restrict total flow from pump.

Then you need to do it as designed by the manufacturer; from the raw water pump to the water inlet manifold, through the engine to the exhaust manifold, out of the exhaust manifold to the exhaust elbow...


The 90 elbow (4) on the front end of the exhaust manifold should be hooked directly to the exhaust elbow (5) on the opposite end, though if you wanted to bypass a certain amount of water overboard to reduce flow through the exhaust, this is the traditional place to do it, after the water has done its job cooling the engine...

Yes, water exits from front end of manifold through hose to exhaust at opposite end - can't think of any reason to reduce raw water to exhaust.

On some engines it is advantageous to reduce the amount of water flow through the exhaust for various reasons, generally exhaust restriction or excessive output by the r/water pump. if you don't need this reduction of flow, don't do it.


And finally, certainly a fuel leak can cause hard starting, among other things. Best to get that sorted out, though hard or prolonged starting is, often as not, a case of slow starting (rotational) speed, usually because of bad connections or slightly flat batteries...

Yes, I attributed hard starting to fuel leak. Start battery is good.

Good cables and connections, both ground and hot, as well as the ground connection between starter and engine block, are also crucial to attaining designed starting speed...

Originally Posted by NevisDog

Yes, must try to sort out that fuel drip, but it wasn't a priority, but noticing one hot and one cold cylinder has suddenly made me sit up and do something. It's gradually become more noticeable over past three starts, if that provides any clues. Started off a little bit of temperature difference, next time the difference was enough to get me wondering, but now it's extreme and I have to find out why.

The reason is likely because, as it is plumbed in the picture, there is little flow through the engine as it was designed for, and the pressure from the raw water pump is feeding into the exhaust manifold water jacket at outlet 4.

If the engine was running 'too cool' previously, it is very unlikely that, in the short time you're been playing with it, that any nefarious blockages have developed. Agree it's best to reset to original (manufacturers) setup and proceed from there.

As the engine came from the factory, the fluid flow would be from the raw water pump (1) to the water manifold (2) up through the cylinders to the exhaust manifold, and then out through the exhaust mixing elbow (5), via the cooling water outlet (4).

At between :02 and :04 and :14 and :17 in the video below you can see the proper setup.

https://www.youtube.com/watch?v=3ecm1-RjCss