BX Diesel engine revs on its own !

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David.Cox
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BX Diesel engine revs on its own !

Post by David.Cox » 10 Mar 2002, 00:29

Today my BX 17DTR was quitely ticking over while I waited in a traffic line, when it suddenly started to rev very hard. It sounded like a generator starting up on the building site I was next to, but it was me, and a cloud of smoke out the back. Went home; looked at the linkages on the diesel pump - acc cable etc, and could see nothing wrong, though it was possible something stuck. A short time after it did the same.
I think I probably have to lubricate some of the lever bits on the diesel pump perhaps. However, as far as I recall I was not pressing down the gas pedal when it suddenly revvd up. Had it stayed at high revs after I had got it there I would have understood.
Any tips from anybody about whether there might be something more complicated behind this ???. I seem to remember something about lubricating something on the diesel pump, but Haynes manual only talks about taking the thing apart.
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Dave Burns
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Post by Dave Burns » 10 Mar 2002, 20:52

I think your problem will be mentioned here. (near the end of 3rd block of text)
http://www.tramontana.co.hu/citroen/engine/diesel.html
A good time to aquaint your self with the manual stop lever on the pump.
Good luck
Dave
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Dave Bamber
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Post by Dave Bamber » 11 Mar 2002, 00:53

Is your engine worn? If so, the crank case fumes could be excessive and the engine might be running on these instead of diesel. Is the throttle pedal fouling on the interior carpet, or any mats?
Edited by - Dave Bamber on 17 Mar 2002 17:54:30
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David.Cox
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Post by David.Cox » 17 Mar 2002, 18:25

Rather tardy reply, but thanks to all those who put in posts to help on this one. Have not started looking yet, but will come back with any results in due course, or if there is any further clarification needed.
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David.Cox
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Post by David.Cox » 19 Mar 2002, 06:55

Well, I took fate in my hands and had a look this weekend. stripped down the air cleaner and all the air piping up to almost to the turbo. Aid cleaner was ok, aopart from small amount of oil at the air intake side, which has been normal in the past. inaspected inside all the tubing and could find no obstruction. Small amount of oil in the tubes, in the area of the fuel filter, again nothing unusual, at least not from past experience with this vehicle.
Very cautiously starter engine - ready to stall it if need be. Started a bit lumpy, and was like that for slsightly longer than normal. almost as if it was still getting rid of something like oil on the injectors. Gently drive it down the road, and then it became its nromal smooth self. Then went for bust and did a ten mile run. Turbo responding well. No repetition of the revving.
It occurs to me that in the week prior to the spontaneous revving I had done a failry fast run of nearly 300 miles in extremely windy conditions. Is there any chance that an accumulation of a small amount of oil in the pipes got forced by wind pressure down the pipes and into the manifold, and then got used up. Remember that when it did over rev it did stop of its own accord, indicating that only a limited amount of oil got thru the system.
Have read the article that David Burns pointed to. Engine has always had good oil changes with good quality flushing agents. No signs of excessive wear.
any further commenets folks, as I need to sue the car to do a long run up north in a couple of weeks. Or should I take it to a specialist to check over ?
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David.Cox
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Post by David.Cox » 23 Mar 2002, 08:14

Any thoughts out there ? <img src=icon_smile.gif border=0 align=middle>
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Dave Burns
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Post by Dave Burns » 23 Mar 2002, 15:24

Hi David, don't know if you read the passage that says:
"CAV pumps are incredibly sensitive to air in the fuel uptake: this is because they use hydraulics to transfer certain forces within the pump, most notably to the speed regulator assembly and the turbo boost membrane. It uses the fuel for this, relying on its uncompressibility. Of course, if the fuel has air bubbles in it, they together become compressible which completely screws up the hydraulic stuff. The results are very annoying such as sudden shutouts, getting stuck at 2000 rpm, oscillations (sometimes really bad—from 1000 to 5000 rpm and back, once every second or so), even engine runaway. Very nasty indeed".
Check the leak off pipes for splits and fuel pipe union's, it sound's like it is pulling air in from somewhere.
A diesel wont run on crankcase fumes, at all, since these are mostly combustion gasses that have got there due to piston blow by.
A diesel will run on engine oil, once one start's to do this because of an internal fault or overfilling with oil which causes the crankshaft to dip into the oil and throw large amounts up the bores with some of it getting past the piston's, engine runaway then takes place, and it doesn't stop by its self, switching it off does not stop it either since it has aquired another fuel source.
I once worked for a bloke who broke the dipstick on his 83 Audi 80 TD, he grossly overfilled it as a result and suffered engine runaway whilst driving it, it had to be stalled to stop it.
So I think your engine running on oil can be discounted.
Good luck
Dave
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David.Cox
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Post by David.Cox » 27 Mar 2002, 04:25

Dave, thanks for your suggestions, as it narrows the field a bit.
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