Diesel Running Problem

Hi, I have a Chrysler Voyager CRD 2.5 Diesel. It runs fine when stationary, both on tickover and when reved up. It drives fine upto about 60 mph, but when I take it over that speed it starts knocking juddering and omitting lots of black smoke. Dropped back to 30 mph it takes about 10 minutes to clear and run normally again, with no knocking and no black smoke.

I had a diesel engineer try and diagnose it and reckons spening £1200 on a new set of injectors may help, but he cannot guarantee it will cure the problem.

Check all hoses for signs of softness and collapse pre turbo- sounds line one is sucking flat under boost.

Tim..

Get a different diesel engineer? That doesn't sound like injectors. Find someone local with a rolling road & run it up on that.

If there's no sign of collapsed hoses (also check the air filter), could be the EGR valve. Easiest way to eliminate it would be to block it off.

And even if it was injectors, a decent diesel place will be able to test them out of the car before writing them off.

Hi, I have a Chrysler Voyager CRD 2.5 Diesel. It runs fine when stationary, both on tickover and when reved up. It drives fine upto about 60 mph, but when I take it over that speed it starts knocking juddering and omitting lots of black smoke. Dropped back to 30 mph it takes about 10 minutes to clear and run normally again, with no knocking and no black smoke.

I had a diesel engineer try and diagnose it and reckons spening £1200 on a new set of injectors may help, but he cannot guarantee it will cure the problem.

Whats year, mileage, and past history of maintanance / previous problems?

tim.

Hi and thank you ll so much for offering your suggestions, and thank you for asking for more information Tim.

The vehicle is a 2001 Chrysler Voyager CRD LX with 2.5 Diesel with manual gearbox. It has now done 105,000 miles it has service history upto about 60,000 miles but as I only recently bought it I don't know much else about its history or any of its previous problems.

I had the car in at Chrysler main agents for computer diagnostics and they said that the alternator and diesel pump were showing fault codes, but also said they didn't think there was anything wrong with the alternator.

The diesel engineer also did computer diagnostics and came back with the fault 'p1130 rail monitor leakage'.

He also showed me 4 small 2 inch high pots of diesel which he said were results of an injector test, each pot had a slightly different level of diesel in it which, according to him signified injector problems.

Thanks again - David

Well that implies your injectors are worn, but I still doubt that's whats causing your problem. You should be able to find a Bosch dealer who'll rebuild your injectors much more cheaply than the main dealer.

Right, firstly common railer injectors are not rebuild-able, as a rule.

Unless you have poor cold starting, uneven running or misfires then you can pretty much discount a problem with the injectors.

I would agree you probably are looking towards replacement injectors fairly soon (roughly 100-130k is the norm) due to the slight difference in volumes produced by each, but the spray pattern they are producing is *far* more important than a minor variation in quantity expelled. Your enginneer didnt make any reference to this??

You may have a slightly weepy one way valve in the HP pump which is flagging the leakage monitor, but this will just extend cranking time slightly before it fires up nothing more.

Sudden black smoke and lack of power whilst under load has just got to be the air supply being cut off for one reason or other.

Tim..

How about a pipe with a split which only opens up at high boost - the ECU thinks the boost is high and increases fuelling, but the increased pressure escapes through the split resulting in overfuelling and black smoke out the back.

/jk

No, invariably the ECU measures boost pressure at the manifold AS WELL as montoring air flow in via the AMM, and will notice if there is a descrepancy and then react by pulling back on the fuelling, possibly entering LOS mode, and illuminating the MIL.

Tim..

The only "ECU" on my Pug 306 reads the transponder chip in the ignition key fob and supplies 12v to the stop solenoid on the diesel pump...

/jk

Hi and thanks again for all your contributions.

I will make efforts to have another diesel mechanic to carry out your suggestions in order to try and rectify the problem and let you know if things improve.

In addition, another contact of mine has suggested either cleaning or replacing the Mass Air Flow Meter.

Any other thoughts before we proceed please?

David

Yes, the problem is not the AMM.

Could you please check the oil level as well, i've just re-read your OP and the symptoms are also that of oil-self-sufficency. Causes are the oil level too high, excessive blow by, or a blocked / restricted PCV system - oil is being pushed out of the breather into the turbo and the engine is running on that when under load. In this case the car will want to keep accelorating even when backing off the accelorator; if you dipped the clutch the engine would race out of contol.

Tim..

Could be the timings out!