Common Rail Diesels - Experience

[goboatingnow]

Originally Posted by mabowers

I don't disagree re: focusing on a single failure mode, but I don't want to introduce additional ones.

Just owning a boat introduces a whole lot of single failure modes. The ecu is likely to be the least of your engine worries

[noelex 77]

It is not just problems with the electronic ECU that are a concern. Common rail diesels use a much higher pressure system and are therefore more sensitive to poor quality fuels.

Poor quality diesel is unfortunately an issue for a long distance cruising yachts.

We do everything possible to ensure clean diesel such as using a polishing system, a day tank etc etc, but installing an engine that is fundamentally more vulnerable to water and dirt etc in the fuel system I think is best avoided while the legislation allows this.

[NBs]

Hi,

more on this topic here. lots of good perspectives to think about.

at best i think maybe how many speakers on mechanical dies have special tools to repair / adjust the injectors, mechanical fuel pump and in addition spare parts for these. how many of you could do this job?

Few people can troubleshoot a diesel engine or repair the engine far and wide.

https://www.cruisersforum.com/forums/f54/common-rail-marine-diesel-engine-v-standard-202707.html

Turbos are already about s 100 years old in marine engines and even more so are feared🥵

NBs

[Symphony]

Originally Posted by Scubaseas

I think your biggest issue would be getting anything related to the common rail system serviced. Both diagnosis and repair may entail factory tools or pricey after market ones plus a mechanic that has them and knows when to use them I have a business that uses Yamaha outboards and while we have aftermarket software and a code reader to use a laptop to replicate the factory diagnostic tool none of the local "talent" has any clue of how, when or why to use it.

This is true, but mechanical systems use injectors, and if those are damaged or fail you won't be rebuilding or repairing with hand tools in your galley. You need a shop with equipment. So, if you plan to be away from industrialized seaports, it's more reliable to bring along a pre-programmed plug-n-play ECU than injectors and pump.

IN my experience both types of diesel have been very reliable.

[goboatingnow]

Originally Posted by Symphony

This is true, but mechanical systems use injectors, and if those are damaged or fail you won't be rebuilding or repairing with hand tools in your galley. You need a shop with equipment. So, if you plan to be away from industrialized seaports, it's more reliable to bring along a pre-programmed plug-n-play ECU than injectors and pump.



IN my experience both types of diesel have been very reliable.

Correct. Focusing one one aspect , the ecu, is quite ridiculous

[waterman46]

Originally Posted by Symphony

This is true, but mechanical systems use injectors, and if those are damaged or fail you won't be rebuilding or repairing with hand tools in your galley. You need a shop with equipment. So, if you plan to be away from industrialized seaports, it's more reliable to bring along a pre-programmed plug-n-play ECU than injectors and pump.

IN my experience both types of diesel have been very reliable.

The injector on an ECU engine, being an electro-mechanical device, must be inherently less reliable than a dumb mechanical injector.


And I don't understand why replacing a failed injection pump with a known exact replacement is a less reliable process than replacing a pre-programmed ECU. Messy perhaps, more difficult perhaps, but no less reliable as long as you know the process.

[RaymondR]

It's nonsensical to suggest that the old, purely mechanical diesel fuel systems cannot be repaired in the field with hand tools commonly found in a mechanics toolbox. They have been for centuries.

[donradcliffe]

I delivered a boat with Cummins common rail engines. The first day I went to start them, all I got was red triangles on the display with a note to call the dealer. I checked everything and tried again, and they ran fine for 1200 miles. The ECU was just telling me who was in charge.

I now have an RV with a Mercedes Benz 6 cylinder diesel. It used to be a good reliable and economic engine, but now it has Diesel Exhaust Fluid, Particulate Filters, and more unreliable crap hung on it. The ECU has about 48 terminals One of them runs the windshield washer motor, and it decided not to. Rather than take it to a MB dealer for a new ECU, I ran my own wire to the washer motor.

[Dieseldude]

Originally Posted by RaymondR

Don't do it.

There are few complex mechanical devices more reliable than the older diesel engines with entirely mechanical fuel systems and with the engine in a boat if you really need the engine you really need it.

Agree! Well designed and well manufactured mechanical injection systems are the most reliable, and most easily repaired fuel systems. They are not reliant on a complex computer and sensor system. Common rail systems can certainly be more efficient. But they introduce needless complexity that can be very difficult and expensive to troubleshoot and repair. If considering a common rail engine, one important item to research is the cost of a spare fuel pump compared to one for mechanical injection. Also the cost to overhaul both. Fuel system parts in general can be much more expensive than those in mechanical systems. Plus there is the multitude of sensors and the computer control system.



If someone has a vessel that was built before strict emission requirements were introduced, they would be well advised to stay with an engine that has mechanical injection. If this means overhauling their old engine, or purchasing a professionally overhauled mechanically injected engine, it would be more reliable than a modern common rail engine. Mechanically injected engines are very much an asset. Common rail engines can be a costly liability when they fail.

[Dieseldude]

Originally Posted by donradcliffe

I delivered a boat with Cummins common rail engines. The first day I went to start them, all I got was red triangles on the display with a note to call the dealer. I checked everything and tried again, and they ran fine for 1200 miles. The ECU was just telling me who was in charge.

I now have an RV with a Mercedes Benz 6 cylinder diesel. It used to be a good reliable and economic engine, but now it has Diesel Exhaust Fluid, Particulate Filters, and more unreliable crap hung on it. The ECU has about 48 terminals One of them runs the windshield washer motor, and it decided not to. Rather than take it to a MB dealer for a new ECU, I ran my own wire to the washer motor.

Engine and vehicle designers have gone mad with computerization. When these systems were first introduced, they were computerized engines. Now they have become motorized computers. Making a peripheral device such as a windshield washer reliant on an engine control computer has to be the ultimate in needless complexity. Why would the engine need to control the windshield washer? All that should be required is a switch and a perhaps a relay.

[goboatingnow]

Originally Posted by Dieseldude

Engine and vehicle designers have gone mad with computerization. When these systems were first introduced, they were computerized engines. Now they have become motorized computers. Making a peripheral device such as a windshield washer reliant on an engine control computer has to be the ultimate in needless complexity. Why would the engine need to control the windshield washer? All that should be required is a switch and a perhaps a relay.

Because it’s cheaper and more reliable then a relay it also means you don’t need full wiring looms , wiring is more expensive then electronics. Usually wipers are controlled by the body computer , using the ecu for this is unusual

[Dieseldude]

Originally Posted by goboatingnow

Because it’s cheaper and more reliable then a relay it also means you don’t need full wiring looms , wiring is more expensive then electronics. Usually wipers are controlled by the body computer , using the ecu for this is unusual

Just because something is cheaper initially does not make it less costly over time. Old basic switch and relay controlled devices are much easier to troubleshoot, having few components. Wire is not a factor in cost. Wire is still needed to get from the switch to the computer, and from the computer to the washer pump. Computers are not high current sources, so a relay is still required. Why would a vehicle require a "body computer"? Body mounted electrical devices have existed for decades with no computers. Switches, relays, and wires are very reliable, and much simpler to troubleshoot and repair. Needless computerization introduces higher repair costs.

[Dieseldude]

Originally Posted by noelex 77

It is not just problems with the electronic ECU that are a concern. Common rail diesels use a much higher pressure system and are therefore more sensitive to poor quality fuels.

Poor quality diesel is unfortunately an issue for a long distance cruising yachts.

We do everything possible to ensure clean diesel such as using a polishing system, a day tank etc etc, but installing an engine that is fundamentally more vulnerable to water and dirt etc in the fuel system I think is best avoided while the legislation allows this.

Good point about the increased pressure and problems with poor quality and dirty fuel. Old mechanical injection systems are much more robust.

[bcboomer]

OT, but.
Body controllers are used for things like intermittent wipers, rain sensors, automatic temperature controls, automatic locks, blockage sensing power widows, cruise control, automatic headlights, daytime running lights, backup cameras, etc., etc., etc.


You can't do this stuff without a computer.

Yes, there will be an adjacent relay block for high load items.

[Dieseldude]

Originally Posted by bcboomer

OT, but.
Body controllers are used for things like intermittent wipers, rain sensors, automatic temperature controls, automatic locks, blockage sensing power widows, cruise control, automatic headlights, daytime running lights, backup cameras, etc., etc., etc.


You can't do this stuff without a computer.

Yes, there will be an adjacent relay block for high load items.

I have a late 90's Dodge Ram that has intermittent wipers, power locks, power widows, cruise control, and daytime running lights. And it has no body computer. Back up cameras can be independent of computer control. A computer for these is a needless complexity. If some people want the needless extras, then they should be free to have them included. But burdening all purchasers with needless expenses is not necessary. Auto manufactures have gone computer mad.