Turbo cut-out

[maysons]

Just to say sorry before I start, but I’ve bought a caravan! My problem is, whilst towing with my recently purchased 01, E320 CDI saloon, the turbo seems to cut-out and the car reverts to a standard diesel engine, with plenty of power low down but no top end. I have been told that a restart will reset the turbo but mine doesn’t cut in again until after a couple of days driving without the van. Any Ideas out there?

 

[television]

As far as I know there is no turbo re set, how do you know that the turbo is not working, are you sure that the fault is not more MAF related.
I think that you will have to get the fault code read out to be sure on thid one.

Malcolm

 

[maysons]

Turbo

Thanks for reply. The turbo is quite noticeably absent when it does go down, and it only happens when towing, I don’t push the car but we have an immediate steep hill to climb to leave home. When the van is unhitched at destination and we are using the car on its own, the power is just not there, and the "whistle" / "whine" is also gone, when it does come back on after a couple of days the performance is back to amazing.

 

[television]

I will see if I can find something later in the day.

malcolm

 

[maysons]

Tubo E320 CDI

Cheers Malcolm. I’ve decided to book it on to my preferred MB dealership`s diagnostic on Monday morn to see if a code comes up. I will post the outcome as soon as the fault is diagnosed / rectified. Regards. Richard.
ps. just enjoyed last 15 years with a F reg 260E saloon

 

[aaron6155]

hi there it will depend on what fault codes are found but there are a few common things we have found with that engine, the main cause we find is the egr valve sticking and the turbo is then not controlled fully so it gets shut down, the fault code though can be very deceiving in saying "mass air flow sensor".

 

[psmart]

A number of possibilities here, firstly, get the fault codes, BUT these may not tell you the whole truth:

A fault code can lead you to a particular device, but here are some of the main areas too look at:
a) the Boost Pressure Control Valve Transducer. This is a device which controls the Turbo's actuator which in turn controls the amount of exhaust gasses which are directed on the VNT and thus regulate the boost pressure. This device sits near the left hand sidewall of the engine compartment and has two small pipes feeding into the top, two wires lower down and has what looks like a fuel filter at the bottom.
b) the EGR valve transducer. As per a), an almost identical part, but sits on the bulk-head and regulates the opening of the EGR valve.
c) Boost Pressure Sensor - this device sits on the intercooler at the inlet manifold side and tells the ECU the air pressure being fed into the engine. This is used to work out the amount of fuel etc.
d) The Mass Air Sensor (MAS/MAF) not sensing the correct airflow.
e) A leak in the vacuum system, thus not letting devices in a) or b) function correctly.
f) A leak in the post Turbo to Inlet Manifold ducting/piping/Intercooler. You should normally here a whistle or wheeze, but with this condition, the ECU will sense that there is insufficient boost pressure for the amount of actuation of a) and shut the turbo down.
g) Exhaust system has clogged up, causing the Turbo not to spin-up to the correct speed, and in combination with a) and c), the ECU will sense an out of parameter fault and shut the turbo down.
h) A gearbox fault, such as overheating etc, which will shut the turbo down.
i) Almost any electrical fault which puts the engine into Emergency mode.

As the problem is only occurring when you are towing, ie. putting the engine on extreme load, then it looks like you are going into the boundaries of ECU parameterisation, and any one thing slightly old or worn or out of spec could cause the problem. Another possibility is that the Turbo is not able to give the correct boost pressure required by the ECU whilst towing due to the Turbo being worn or its actuator mechanism being out of spec. The latter can easily be corrected by a turn on the actuator arm adjuster.

With you saying that the symptoms still persist after you have un-hitched for a couple of days, then b) or g) sound the most likely.

Post the fault code and dont authorise Mercedes to do any work, as it could be a simple 10 minute job for you to rectify.

For instance, the 'air filter' units on a) and b) can get clogged, they did on mine, and these in turn can affect the transducer operation, leading to the ECU shutting it down.

Ill just add to this, on these engines, it is impossible to actually shut the turbo down. This is because they are using a Variable Nozzle mechanism to direct the flow of exhaust gasses over the turbine. The turbo uses a much smaller compressor blade than a waste gate type turbo, and thus the airflow into the engine is highly restricted, so if the turbo were to stop, the engine would most certainly die due to lack of air. On the actuator arm, there is a minimum stop position, adjusted by a thread locked screw, so when the ECU de-activates the Boost Pressure Control Valve Transducer (or there is a vacuum failure) then the actuator goes to the minimum position pre-set by this locked screw. This thread locked screw setting is critical, as it sets the minimum speed at which the turbine/compressor will spin for a given in-rush of exhaust gasses. Should this screw be set too low, then a condition called surge will occur, where the pressure in the inlet manifold is higher than the pressure the Turbo turbine is producing, causing the blades to stall and possibly shear/damage the bearings (this condition normally only occurs when the engine is under heavy load, ie. towing, so this perhaps is another possible area for your fault).

Also, c) above, when I was fault finding and swapping parts from a 220 to a 270 I discovered that the Boost Pressure Sensor was loose on the 220. Although no fault had been seen on the 220 (rarely goes above 70mph), boost air would have been leaking past it, so it is a possible check area, as perhaps these sensors are not well secured.

Sorry to keep on adding to this post, I keep on recollecting more info. Another device, although less likely, is the Charge Air temperature sensor, located on the Intercooler at the headlight side, top right hand side. This device tells the ECU how hot the air is going into the inlet manifold. If its faulty, could tell the ECU that it is pumping very hot air (or very cold air) into the engine, which would be outside of parameterisation, thus emergency mode would be engaged.

 

[maysons]

Thanks for the advice. As a very junior member I didn’t realise the wealth of information and knowledge available out there. As I have only had the car for 6 months I presume the work will be under the used car warranty, my reason for asking for help was to try and avoid making several lengthy trips to the dealership to sort the problem out.
I remember a fault on my last Merc, an 88 Auto 260E. At traffic lights, or in a queue of vehicles on tick-over, the engine used to suddenly rev. trying to push you into the back of the car in front, quite unnerving, and then it would be ok for weeks. I lost count of the journeys to the MB garage. In the end they gave me a loan car and a technician used mine for a week or so, wired up with gauges until the fault reappeared or rather manifested itself. It was the engine management unit at fault and they only charged for the parts as a goodwill gesture. (Dalesview, Clapham, North Yorkshire, no longer MB. shame.)
I will post the outcome.
Regards Richard

 

[OlafMaxwell]

I had a similar problem. It was the MAF, its not an expensive item and is easily fitted. Mine was replaced somewhere about 95/90k but i know many have failed sonner than that.

 

[psmart]

I had a similar problem. It was the MAF, its not an expensive item and is easily fitted. Mine was replaced somewhere about 95/90k but i know many have failed sonner than that.

As most of these problems are down to the MAF, it sounds feasible, due to the increased demand for airflow over it whilst towing, but what doesnt make sense is that it takes 2 days to recover. aaron6155 sounds very feasible with the sticking EGR valve, also with these transducers, as they are needle valve based and could stick.

What gets me though is that there are all these MAF failures, but the MAF lives on the clean side of the air tract, before the Turbo, before the rocker/crankcase breather etc, whereas the Boost Pressure Sensor lives in a hostile, hot, high pressure environment with oil mixed in and doesnt seem to fail all that often. Also the Charge Air temperature sensor lives in these same conditions.

 

[Uncle Benz]

Just to add my 2p to these excellent suggestions. I have heard of, but not seen, a fault with a flap in the plastic inlet manifold that comes loose and restricts airflow, mainly under heavy load, and then randomly drops away again, sometimes much later. A local garage brought a car to me with this type of fault, but I was very busy so they took in to main dealer who found the cause and replaced the inlet manifold.

 

[television]

As most of these problems are down to the MAF, it sounds feasible, due to the increased demand for airflow over it whilst towing, but what doesnt make sense is that it takes 2 days to recover. aaron6155 sounds very feasible with the sticking EGR valve, also with these transducers, as they are needle valve based and could stick.

What gets me though is that there are all these MAF failures, but the MAF lives on the clean side of the air tract, before the Turbo, before the rocker/crankcase breather etc, whereas the Boost Pressure Sensor lives in a hostile, hot, high pressure environment with oil mixed in and doesnt seem to fail all that often. Also the Charge Air temperature sensor lives in these same conditions.

The EGR valve cannot effect the genral running of the engine, if stuck open ,or part open the idle will be rough, but will not affect the turbo or normal driving.

I was going to say earlier on that this should be the MAF, but dismissed it on the time taken to recover, but there are some bits in this thread that remind me that it could very well be that.

Deisels do have some oily fumes and as can be seen here, the deisel MAF's only go half the distance of a petrol before cleaning or replacement is required. the turbo is operated through the airflow through the engine, maybe with the van on tow the air flow can get reduced.

Let us say that your MAF is on the point of needing replacement or cleaning and towing just brings that about, clearing after two day could be accounted for by the extra clean air passing over the MAF. Don't forget here we are talking about a hair like wire 25mm long,that need to be clean.

It has to be the MAF.

Malcolm

 

[psmart]

The EGR valve cannot effect the genral running of the engine, if stuck open ,or part open the idle will be rough, but will not affect the turbo or normal driving.

I was going to say earlier on that this should be the MAF, but dismissed it on the time taken to recover, but there are some bits in this thread that remind me that it could very well be that.

Deisels do have some oily fumes and as can be seen here, the deisel MAF's only go half the distance of a petrol before cleaning or replacement is required. the turbo is operated through the airflow through the engine, maybe with the van on tow the air flow can get reduced.

Let us say that your MAF is on the point of needing replacement or cleaning and towing just brings that about, clearing after two day could be accounted for by the extra clean air passing over the MAF. Don't forget here we are talking about a hair like wire 25mm long,that need to be clean.

It has to be the MAF.

Malcolm

If you disconnect the EGR control transducer, simulating a fault, the engine goes into emergency mode and disables the Boost Pressure Control Valve Transducer, which basically is stopping the Turbo from spinning up past its minimum setting. Same if you remove the vacuum to it. I went through all these scenarios with my CarSoft software whilst attempting to locate my turbo fault. Everything Ive suggested above has been tried out. You can disconnect the MAF and run the engine, and it wont go into emergency mode unless you put the engine on load.

On the 270, the MAF is located before anything which can contaminate it, other than a filtered airstream (unless the filter is broken). The crankcase/rocker breather is after the MAF and just before the turbo compressor inlet, so NO oil should be able to get onto the MAF, unless a back current is setup! Checkout my earlier threads, at 60000 miles, the MAF was as clean as a babys but!

Lets see when Maysons gets his codes read out, will be interesting to see. I cant see howa hot wire and a wheatstone bridge can take days to recuperate!

 

[television]

Yes we shall see, one must keep in mind that every MAF filter is in the clean air flow, we must not forget that breathing of the engine can find its way back, We have more threads on a dirty MAF than any other, and its the diesels much more than petrol.

The EGR valve only comes into use at light throtle and cruising.

Re the fumes or breathing of an engine. if fumes can rise from the sump to the underside of a Dizy cap and rotor arm, then they will go anywhere, and do, OK I am very happy to learn something new, But the MAF is the only vairible factor, as you say it will be nice to know, if the fault codes show everything wrong,other than the MAF, then it is the MAF. I am happy to be wrong,and learn something new.

Malcolm

 

[psmart]

Yes we shall see, one must keep in mind that every MAF filter is in the clean air flow, we must not forget that breathing of the engine can find its way back, We have more threads on a dirty MAF than any other, and its the diesels much more than petrol.

Have you felt the suction from the turbo compressor inlet, even when in the disabled mode? It can rip your skin off. Given that the breather outlet is only some 10 cm away from it, I cant see how oil can get back into the MAF. There is only one way I can see, and thats through the airfilter, if its knackered, and then its oil scum from other vehicles.

Could be different diesel/turbo diesel design where the oil gets onto the MAF, Im only quoting from the 2 cars I know intimately, a 220cdi and a 270cdi, same design and same as the 320cdi, all inline, with the basical overall design being the same.

You may learn something new, I may learn, thats what its all about, your never too young to keep on learning

 

[maysons]

Lets hope that the technicians at MB South Lakes know as much as you guys do.
I shall present all your opinions for their examination and ask for a suitable reply to post. Regards. Maysons.

 

[television]

. There is only one way I can see, and thats through the airfilter, if its knackered, and then its oil scum from other vehicles.


You may learn something new, I may learn, thats what its all about, your never too young to keep on learning

All engines need to breath, this is done by venting to the inlet, the EGR valve
also vents to the inlet.

Malcolm

 

[maysons]

Just pulled the electrical contact plug off the MAF and its very dirty, I should actually say, "wet" on the inside of the terminal block with a thin black oil. The surrounding area and hoses seem fairly clean and dry, so it does look like there is contamination coming from inside the unit as its also pointing slightly downwards. I will post the outcome of visit to MB tomorrow. Regards to all. Maysons

 

[psmart]

Just pulled the electrical contact plug off the MAF and its very dirty, I should actually say, "wet" on the inside of the terminal block with a thin black oil. The surrounding area and hoses seem fairly clean and dry, so it does look like there is contamination coming from inside the unit as its also pointing slightly downwards. I will post the outcome of visit to MB tomorrow. Regards to all. Maysons

If this is the problem, dead easy to sort out, but things to consider are that the previous owner may have had problems and he sprayed contact cleaner/wd40 onto the contacts (I have done this on all my sensor contacts, to keep them in pristine condition, using contact cleaner and then spray grease to disperse water). If it is oil from inside the air tract, then actually getting oil into the contacts, from the MAF, sounds bad indeed. I still disagree with Malcolm because I cannot see any possible way (at least on the 220cdi and 270cdi) of oil getting onto the MAF, except through a damaged airfilter, and then it would be oil scum.

The EGR on these engines works by an extra port on the Exhaust manifold, at the bulkhead, which goes through the cylinder head and on the inlet manifold side (seperate from the inlet manifold intake), it is fed into a cooling chamber before being fed to the EGR valve which sits at the entrance to the inlet manifold. The intercooled aircharge is fed into this chamber as well, so no exhaust gasses can get into the MAF.

Maybe on the 320cdi there is a slight design difference (I dont think so, because the exhaust manifold gasket is the same for the 270 and 320, you just chop off one of the cylinders gasket), or perhaps the crankcase/rocker breather is fed before the MAF, but certainly on the 220 and 270 it isnt.

 

[maysons]

Turbo Troubles

Looks like the MAF was at fault, MB South Lakes replaced it under "used" warranty and only charged me £17.20 for a new air filter as it was badly contaminated. So with luck thats problem solved, though I wont know for sure until I take the Van out again next week. I will keep you all posted. Many thanks. Maysons.