Engine revs in the millions

bubber · Post by **bubber** » 28 Oct 2008, 13:14

Hello all,
I have a '92 405 TD with inter cooler. The other day it decided to rev to the point of explosion. I have never seen a car rev that high, the whole street disappeared in black smoke. It is not a sticking cable but seems to be the injection pump.
Car starts as normal, ticks over fine and then whoosh it's off again.
I am a little worried that such high revs may have caused other unknown as yet damage.
Any help and advice would be very welcome.

P.S. It is an old 'un but in OK condition, 70,000 , new cambelt at 45,000.

Many thanks

Post by **CitroJim** » 28 Oct 2008, 13:18

You are right to be worried

How did you stop it?

It's more than likely consuming its own engine oil. A mechanical injection pump very rarely causes such a problem although it can.

The most likely cause, and from your description, is failed valve stem oil seals. Does it smoke a bit of blue smoke if idling for a while and then opened up?

No damage will have resulted. The engines are built like tanks...

bubber · Post by **bubber** » 28 Oct 2008, 18:35

Thanks for reply,
It does smoke a little but not excessive, no more than it has in the years I've had it.

The only way to stop it is to turn off, even then it runs on of it's own momentum.
The amount of fuel that must be being injected to rev this high is scary and the amount of smoke, is fog like, I did check engine oil and the level seems normal.The engine sounds like a pneumatic drill when it happens.

jgra1 · Post by **jgra1** » 28 Oct 2008, 18:42

it has to be oil burning ...
if the start solenoid was iffy it would idle a bit after you switch off, but it wouldnt rev as well..

maybe oil has filled up the inlet pipes, filter?

on a different note, just went into a motorbike workshop and commented on how nice and warm it was

chap said the space heater was running on waste oil,

went outside to my running xanita, and I said it was too .. he said it shouldnt be

meaning burning oil

was a big pause when I explained it really was running happily on waste oil

wheeler · Post by **wheeler** » 28 Oct 2008, 23:17

Have you checked the oil level ? Could well be the turbo seals failed sucking up oil & squirting it straight into the intake.

uncle buck · Post by **uncle buck** » 29 Oct 2008, 09:57

When a diesel engine runs on it's own oil turning the ignition off to stop it won't work ....the only way to stop it is to stall the engine.... try to stall it as soon as you can or the engine will suffer damage if you just let it go

Check the Oil level & make sure it hasn't been over filled...the level should be half way between the MAX & MIN.

As wheeler mentioned failing Turbo seals is a common cause of this problem on TD engines.

bubber · Post by **bubber** » 29 Oct 2008, 18:36

Many thanks you guys,
I will follow your advice and check turbo seals and oil level again.
As a matter of interest how difficult and how much to do seals if that is problem?

Thanks again, it is very much appreciated.

uncle buck · Post by **uncle buck** » 29 Oct 2008, 22:07

The seals aren't a DIY job.....you will have to fit a second hand/ recon or new Turbo to sort it out if that's the problem.

Take the intercooler off & if its got loads of oil in it, it will show if the seals have gone....a thin coating of oil in the intercooler is normal.

Post by **CitroJim** » 30 Oct 2008, 08:21

If the seals had gone to that extent, I would have thought you'd see clouds of white/blue smoke, not black.

I'm a bit puzzled. If a diesel starts to consume its own oil, usually it's a runaway problem and it will not stop on the key. Only way to stop it is to stall it or deprive it of air.

I've known a 306 1.9TD that had failed valve stem seals. This manifested itself as a knock and minor runaway when coming off an extended period of idling. A big puff of blue smoke out of the exhaust. I proved it was this by effectively bypassing the turbo by disconnecting the hose at the intercooler so the engine was effectively running as an NA. It still did it.

A good thing to check on the oil side is the crankcase breather system. If it's blocked, exces crankcase pressure might force oil where it should not be.

Re-reading the description, it looks like the pump might be at fault and because the smoke is black, it suggests it is diesel being burned, not oil. However, assuming it's a Bosch, I cannot see what is causing the problem as the centrifugal governor should step in and bring things under control. The Bosch pump is pretty much failsafe in respect to runaways. It's hard to see how the pump governor or the spill sleeve could fail such that the engine ran away. Potentially a blockage in the HP plunger could cause this and due to the design of the pump, the stop solenoid will eventually bring the engine to a stop but not immediately.

On a Lucas pump, should one be fitted, there are circumstances when air leaks on the fuel supply side can cause strange behavious but again, the mechanical governor should bring everything under control.

Odd. Keep us posted on this..

bubber · Post by **bubber** » 30 Oct 2008, 08:22

Unclebuck,
Will do, many thanks for your reply,time and advice.
re-con turbo and work sounds expensive and tricky, car is at that point of whether it will be cost affective. These things can soon become a money pit.

Many thanks, all the best.

Post by **CitroJim** » 31 Oct 2008, 07:57

Last evening I critically examined a Bosch pump to see if there was anything that could cause the governor to fail and cause an overspeed. Essentially, the governor is gear driven from the main driveshaft in the pump. The governor has four weights that throw out on increasing speed and as they throw out they push a plunger that works directly on the throttle plate and spill sleeve. It's such a simple and robust device, failure is almost impossible. There is just one possibility. The drive gear on the main driveshaft is flexibly coupled and picks up drive through two small rubber blocks, a bit like a motorcycle "cush drive". It is possible, but highly unlikely, that the two rubber blocks could have broken up and as a result, positive drive to the governor is being lost. It is about as likely as England winning the Word Cup though, unless the car has, at some time, run on some strange fuel that has dissolved the rubber blocks.

Does the car in question use any oil at all?

bubber · Post by **bubber** » 01 Nov 2008, 13:04

Hi all,
Having asked around a bit, everyone is as confused as to the cause of this problem. It seems that being able to switch off at the key rules out several causes, as you say with the turbo.
I have checked engine oil and I have never overfilled it, level is correct now and it has never used oil. Someone has suggested the dump valve???
One thing I have noticed is that at times it feels like it is only running on 3 pots as it is very lumpy. Maybe there is a sticking or damaged valve? but would this cause the over revving?
I showed a semi mechanical friend the prob, car started fine ticked over lumpy for 30 secs, settled down to normal, let it tick over 2 mins more and then whoosh, it was off and so was he.
He said he'd never seen a car rev that high, you couldn't do it from the pedal cos of the external governor.
Left to run this engine would undoubtedly explode.

Many,many thanks for your time and help.

Post by **CitroJim** » 03 Nov 2008, 10:17

It really looks like the pump is duff. Get it swapped as soon as possible. A scrapyard should provide relatively cheaply but try to get a pump off a recently scrapped car as over time, all sorts of nasties happen to diesel pumps that stand with diesel in them. Have a look in the Blogs section of the forum to see what can happen to a long-standing pump!

Any pump from either a Citroen or Peugeot 1.9TD of the period will do.

If you do swap the pump, I'd be interested in your old one to discover what went wrong with it.

Where are you located?

bubber · Post by **bubber** » 21 Jan 2009, 19:19

Hello citrojim and all,
Bit of a late reply but I have just found out the problem with car.
It is pumping fuel into the intercooler. I'm told it is the valve on the underside of the (Lucas) pump.
As the car is 18 years old ( but with only 100k), I am deciding whether the cost of repair is worthwhile.
Anyway if I do it will be for the Mrs as in a mad fit I've gone and bought a 2000 Citroen dispatch 2.0 hdi, which after 3 weeks has a turbo problem, cars don't you just luv 'em?
See you on the citroen forum. LOL

Thought I would just let you know pug problem for any future reference.
Many many thanks for your time and help

AndersDK · Post by **AndersDK** » 21 Jan 2009, 19:56

Ahhh -

I belive that would be the map compensator pod on the pump that has a punctured membrane.
Thats a cheapo and easy repair AFAIR.
No adjustments or tunings to do, just replace membrane and you are flying again.