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Old 27-08-2017, 20:48   #1
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New Yanmar 4JH-CR series common rail- any firsthand feedback?

I have read and heard lots of concerns about the new common rail diesels- mainly dependence on electrical equipment and vulnerability to a lightning strike, and dependence on pristine fuel. So I think they many not be the choice for remote cruising.
But the CR technology promises to be quieter, smoother, more fuel efficient, and cleaner.
My question is- how reliable are these engines, and how suitable are they for the average sailboat cruiser who stays coastal and buys fuel from "on grid" sources? Most new boats now are equipped with these, and I am wondering what folks have experienced.
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Old 27-08-2017, 22:46   #2
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Re: New Yanmar 4JH-CR series common rail- any firsthand feedback?

Main Advantages:

1) CRDi ensures the fuel injection timing, quantity of fuel and atomisation or fuel spray are controlled electronically using a programmable control module. This allows multiple injections at any pressure at any time (within pre-defined limits), providing a level of flexibility which can be exploited for better power, fuel consumption and emission control.
Noise, vibration and harshness (NVH) are improved with CRDi as a result of the timing flexibility.
2) Your engine sounds quieter and has a better quality of sound. It also runs smoother. You will see fuel consumption benefits as well because greater injection pressure produces a finer spray of fuel (atomisation) that burns more efficiently.

3)Better combustion efficiency is a key part of meeting emission standards. Less fuel is wasted as soot or particulates in the exhaust and deposits in the engine. A cleaner running engine is good for the environment and for the cost of ownership. Cleaner running improves the long-term durability and reliability of your engine.

4) These days normally very reliable


1)Cost Disadvantage

2) A diesel engine with a common rail injection system can cost as much as twice than a diesel engine without a common rail system(But getting cheaper as more commonly used).Price is also driven up by the Electronic control unit, which is a very technologically advanced, key part of the whole Common Rail System

2) If injectors become, even slightly, fouled they can fatally malfunction.
You must hire a certified mechanic to work on a Common Rail Diesel
All the parts of a CRD are very delicate and can break more easily than conventional injectors.

3) Normally requires dedicated shop technician or plug in diagnostic device to trouble shoot,

I have never been called on to diagnose a failed ECU due to lightning strikes, radio's , electronics in general (YES) , most ECU's these days are build pretty hardy and designed to accept harsher punishment,

Today on the larger commercial engines (200 Hp up) it's really hard to find a conventional diesel as all the major manufacturers now only use Common rail systems as does nearly all car and truck engines.

For me, personally (and a bit older) I would rather have a conventional diesel for cruising applications (got to love the old GM's/Yanmars/Perkins/Fords and my favorite GARDNER)

Cheers Steve
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Old 29-08-2017, 05:02   #3
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Re: New Yanmar 4JH-CR series common rail- any firsthand feedback?

Yanmar mechanics in the West Palm
Beach area couldn't fix my common rail electronics problem. Not well trained and poor Yanmar backup.
Capt. Stuart Bell
Ranger R-25
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Old 14-12-2020, 14:04   #4
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Re: New Yanmar 4JH-CR series common rail- any firsthand feedback?

Just to resurect this 3 year old thread.

Has anyone any comments on the reliability of these Yanmar Common Rail engines, especially the JH range?

There must be hundreds installed by now. Surely someones been hit by lightning/ had dirty fuel/ damaged the wiring harness/ called out Yanmar?

Is there a practical way to read fault codes? They are listed in the engine manual.

Would be great to hear of first hand experience, thanks
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