Diesel Engine Won't Stop

aardvark0

Hi,

I have encountered a novel problem with my L reg diesel Peugeot 205 this evening. I arrived home, turned the ignition key as though to turn the engine off, and pulled the key out of the ignition.

I then did a great double take as the engine failed to stop. The revs dropped fairly significantly, and the battery not charging light came on, but the engine kept going.

Putting the car into gear and stalling it with the brake on seemed to sort the problem, but probably not a good long term solution:p . Does anyone have any ideas what the problem might be? At least my problem is not with starting it, so getting it to a garage tomorrow should not be an issue!

Thanks.

bartman

I've no experience of a Peugeot diesel, but the problem is almost certainly due to a solenoid operated fuel switch not closing when the electriciity supply to it is cut (ie when you turn the ignition off).
Unlike a petrol engine, it doen't need an electrical supply to a spark plug to keep the engine running, and if the fuel supply doesn't get cut off when the key is turned, it will just keep going, the fuel pump being mechanically operated by the engine!
It shouldn't cost too much to fix, although it might if you take it to a main Peugeot dealer!

withabix

Don't leave it in gear if you park it on the road, as it could start if someone nudges your bumper!

aardvark0

Thanks for that! It may be useful to get to the garage armed with a little knowledge tomorrow!

Thanks for the tip regards not leaving it in gear. :eek: I am sure it would make for an interesting insurance claim!

epninety

As Bartman says, it's likely due to the diesel shutoff solenoid sticking. That is usually a fairly easy fix (on older diesels) for a diesel technician (swap it out or clean it).

However, on high mileage engines the reason that it sticks is often due to a build up of swarf caused by wear in the fuel injection pump, which isn't going to be cheap to fix.

That doesn't mean 'run away' as it could go on for a lot of miles without further trouble, but you might want to bear it in mind before spending any big money on other repairs in the future.

oldagetraveller

There should be a manual spring loaded stop lever on top of the injection fuel pump. Usually has "stop" and an arrow stamped on it. Might be better than stalling in gear until the fuel solenoid is replaced. That's probably on top of the fuel pump as well with a single wire attached. Quite simple to change, it just screws out using a suitable ring spanner after disconnecting the wire.

aardvark0

Thanks for the tips everyone.

I took my car to a local garage this morning. The mechanic tested the solenoid and declared that there was nothing wrong with it. He has advised me to take it to a more specialised garage not so local for further diagnosis of the problem. I will do this this afternoon.

Looks like this could get expensive - so it may soon be time to look for another car.

I'll let you know how I get on.

bartman

When he said there's nothing wrong with the solenoid, did he mean that it was in fact operating when the ignition is turned on & off? If so, how did he explain the fact that fuel is obviously getting past it when the ignition is turned off?
I would be very interested to hear the outcome of this!

aardvark0

I found the stop lever on the fuel pump - it even works - thanks for that!

All has become clear! What mechanic # 1 failed to spot this morning was that the rubber plunger that cuts the fuel supply had a slight tear in it. Thus although the solenoid was working perfectly well from an electrical point of view, the fuel supply was not being completely cut off.

A new stop solenoid has now solved the problem.

Thank you everyone!

bartman

Glad to hear that you had a successful outcome!

OrangeProse

Hope it's sorted by now, but there's a possibility it might be 'runaway diesel'.

Runaway diesel can happen on a diesel engine where the crankcase breather pipe feeds directly into the air intake. When the engine starts to wear out, gas can blow past the sides of the pistons and directly into the crankcase, along with oil mist, which then obviously feeds back into the air intake.

The engine will run on this 'mist', increasing the revs. As the revs go up, so does the pressure in the crankcase - drawing more oil mist-laden air with it as it goes, creating a vicious circle.

Ultimately the engine gets to a point where it is running itself, a grim kind of perpetual motion if you like, and turning off the ignition won't stop it.

It will keep running faster and faster until the engine explodes.

The general advice with this is that if it happens, get out of the vehicle and get as far away from it as you can, and wait for the engine to blow up.

Apparently it does occur occasionally on 1.9 PSA diesels, although it is pretty rare. There are warning signs - car using a lot of oil, black smoke, refusing to start easily.

Just something to watch out for.