R320 CDI Engine Suddenly Stalled

[mitaka]

oh trust me there are many other ways to stop a diesel. cam sensors when they get overheated etc., my pump was fine and I got stuck three times...They never figured out my problem exactly...that's wh I am driving R350 now

[Wayne Wu]

Well, after a week of triaging by the mechanics as well as back and forth with their German head office, as expected, they said it is the fuel pump. As such, they put in a new one and that is the end of the story.

The take away on this is, who the hell designed and manufactured this pump? The failure rate is way too high and it is not fault prove or tolerant. This piece is mission critical and I expect a premium piece since I paid premium price for the R Class CDI.

Here is what I learn from this incident when a diesel engine stalls ...
#1. Fuel pump relay heating up and failing.
#2. Ignition coil heating up and failing.
#3. Fuel pump failing.

Need fuel pressure monitored until it fails. Check resistance of ignition coil.

LOL

[willyjp]

on a diesel?

what function does that have?

[Wayne Wu]

BTW, they claimed they changed both fuel pumps both the small one in the gas tank and the high pressure one. No problem yet, so far ...

Diesel engine does not have a spark plug but a glow plug which you need some kind of coil for induction heating.

[Wyatt_Earp]

Mikata and others:

Diesels generaelly don't stop without 1 of two things. 1, lack of air or 2 lack of fuel. So, breaking that down and not knowing exactly what transpired at the shop for $800 it would seem that you are suffering from common air in the injection pump.

If anything fuel related, including a fuel filter was changed in that service you can stall the car very easily with air bubbles in the IP either during start up (after the filter change) or upwards of 60 minutes after. This isn't much to worry about and is a simple fix.

This is not to say that it couldn't be something else but unless there is a code thrown it is doubtful that the CPS or TPS or even the rail pressure sensor is out of range causing a cascading effect of falling on its face dead.

If a crank position sensor is faulty you would first witness hard starts, poor mileage and even some smoke under hard accleration. If the rail pressure sensor is out of range from a malfunction or a tuning box perhaps, the car would knock, surge under cruise control and generally act funny. This is common in the case of poor computer hacks that sell you a plug and play box that adds too much fuel and raises the rail pressure beyond 27,000 psi. Assuming that is not the case then it is also unlikely that it would be the TPS (throttle position sensor) since this is controlled by the ECM which unless fooled somehow is generally bullet proof unless the IP is going out on you which I find a really tough sell on a BENZ.

So, my experience would tell me that it is just a little air in the high pressure fuel system (ie between the injection pump or IP and the injectors themselves).

This can easily be solved by purging the air from the fuel filter, the inlet to the IP (be careful not to do anything on the HP side as it can seriously hurt you!!) or even the HP lines to the injectors themselves.

More often than not anything other than purging the air from the filter should be done by someone who is qualified or at least has some diesel know how.

[Wyatt_Earp]

Originally Posted by Wayne Wu

BTW, they claimed they changed both fuel pumps both the small one in the gas tank and the high pressure one. No problem yet, so far ...

Diesel engine does not have a spark plug but a glow plug which you need some kind of coil for induction heating.

What you are describing here is something that I haven't ever seen on a modern comon rail diesel that is un-modified. The in-tank lift pump (it isn't a fuel pump) is designed to push fuel to the high pressure or injection pump. If you had crap in the tank you can get the inlet screen plugged and cause the injection pump to burn out under the heat of having no fuel to lubricate itself with. Seems simply enough right? Well it is and it isn't. The high pressure side is designed by bosch if I'm not mistaken and is generally regarded as the best in the business for the common rail application.

Although I don't know what the exact pressure is at the IP it can be easily tested and would be somewhere south of 11 psi I would think. On the high pressure side it would be as discussed around 24,000 to 26,000 psi or so.

The most common failure beyond having the in-tank pump plug and die would be to have a poor quality or too high a micron rated fuel filter in the OEM canister. Again, it would be important to determine what the specification on the micron rating is but if it is finer (higher) then 6um you will run into problems on even ULSD if this is the primary filter. As say with a 3 um the filter will plug too fast resulting in little fuel travelling to the IP which makes the unit heatup and break apart from the inside.

If this remains a problem, rigging up a primary and secondary filter system would fix most of it. This can be done with a 12um or a 10um as primary and a 6 or a 3 as the secondary. I would also suggest that changing them more often, at say every oil change, is better than what the book or shop would tell you. Filters are cheap in comparision to pumps as you have found out.

In addition to all of this you can easily build a pressure gauge, complete with isolator and snub valve to read pressure in the cab while you boot down the 401. This would cost around $120 to $170 and is easily obtainable from any truck shop or diesel performance shop that carries ISSPRO gauges. The trouble is that you'd need to find a place to put it in the cab. Buying a cup holder for it is likely not an option since few people would do this to a benz but you could have one built out of fibreglass.

Let me know what you find out. I'm interested to know what the results are.

[mitaka]

Originally Posted by Wyatt_Earp

Mikata and others:

Diesels generaelly don't stop without 1 of two things. 1, lack of air or 2 lack of fuel. So, breaking that down and not knowing exactly what transpired at the shop for $800 it would seem that you are suffering from common air in the injection pump.

If anything fuel related, including a fuel filter was changed in that service you can stall the car very easily with air bubbles in the IP either during start up (after the filter change) or upwards of 60 minutes after. This isn't much to worry about and is a simple fix.

This is not to say that it couldn't be something else but unless there is a code thrown it is doubtful that the CPS or TPS or even the rail pressure sensor is out of range causing a cascading effect of falling on its face dead.

If a crank position sensor is faulty you would first witness hard starts, poor mileage and even some smoke under hard accleration. If the rail pressure sensor is out of range from a malfunction or a tuning box perhaps, the car would knock, surge under cruise control and generally act funny. This is common in the case of poor computer hacks that sell you a plug and play box that adds too much fuel and raises the rail pressure beyond 27,000 psi. Assuming that is not the case then it is also unlikely that it would be the TPS (throttle position sensor) since this is controlled by the ECM which unless fooled somehow is generally bullet proof unless the IP is going out on you which I find a really tough sell on a BENZ.

So, my experience would tell me that it is just a little air in the high pressure fuel system (ie between the injection pump or IP and the injectors themselves).

This can easily be solved by purging the air from the fuel filter, the inlet to the IP (be careful not to do anything on the HP side as it can seriously hurt you!!) or even the HP lines to the injectors themselves.

More often than not anything other than purging the air from the filter should be done by someone who is qualified or at least has some diesel know how.

Never witnessed any of the above such as hard starts, poor mileage or smoke with my CDI and yet the crank position sensors kept giving me problems. The car was running great. After normal operation the crank position sensor will overheat and and the car won't start. Engine will crank but wont start. After 30-40 min after the car had cooled off it stared as if as there was nothing wrong with it...

[Wyatt_Earp]

Well, a CPS unless faulty from the factory can't cause it to stall. It would cause it to not start because it wouldn't know where TDC is but otherwise, I would suspect you had other problems.

When you cool it down as indicated and it starts fine that is a fueling problem - very common from Dodge, VW, GMC and even big class 8 trucks. The IP doesn't like to be warm and under a hard start condition like that it isn't getting any or enough fuel and it goes into protection mode and shuts down. This could, although unlikely cause what would appear as a fault TDC reading on the CPS due only to the hard start from lack of fuel.

[AsianBlackR350]

After reading all these threads about Diesel engine problems, I am so glad that I purchased R350 gas engine which is quieter, cleaner, faster compare to R320 and have no problem so far. Gas mileage is not an issue for me.
I have to admit diesel engine last longer than gasoline engine and the torque in R320 is great for towing but I do not tow any boat or others so no need for me.

[Wyatt_Earp]

See, I completely 100% disagree. Diesel is cleaner, more fuel effecient and delivers far better return on investment then a gasser. The reason why more than 60% of new cars and trucks on the road in other countries are diesel is that they outlast all others.

Granted there are a few things that are very different with an oil burner than a gasser but once you educate yourself on those items and know what to look out for then it is pretty much a breeze. The problem in the US and CND is that there are generally few specifically trained diesel technicians in the dealerships and this makes things difficult at times. Especially if you are trouble shooting something as described here.

I'm glad you are happy with your gasser but I'll keep all of my diesels... Cheers,