OT: Pinking Diesel Engine

[Cursitor Doom]

That doesn't actually answer the question, though.

[Andy Burns]

I think the point is the engine was designed under Rover just before the sale to BMW.

[polygonum]

And teaching it Cartesian doubt. I think. :-)

[NY]

Sounds very nasty. My first boss kept a piston from a (petrol) Rover SD1 on his desk. It was a mangled mess with holes punched in the top and the side ripped open where the piston had pulled away from the conn rod. Apparently his timing belt/chain had failed and a valve had collided with a piston. That's when I first learned that some petrol engines are "interference engines" and some aren't - ie whether the valve at the lowest point of travel and the piston at TDC overlap, a situation which never happens - unless the timing fails because of a snapped belt/chain. I'd just bought my first diesel (the Pug 306 with XUD engine) and he said "whatever you do, make sure you replace the timing belt at the stated mileage and don't leave it, because *all* diesels are interference engines: in other words it's 100% certain that the valve(s) and pistons *will* collide if the timing fails. I didn't know about the insert, though :-(

Ah, finer droplets so no glow plugs at all. I ought to have noticed that each cylinder on the HDi only has one connection to it - the fuel injector line - and not a second one - the wire to the glow plug.

I remember the XUD had a little rubber bulb in the fuel line just upstream of the branches to the injectors. It was something to do with sucking fuel manually in case of an air lock. At least with injectors, there's no way that excess fuel can get into the cylinder, unlike in the days of carburettors and petrol engines: I had a friend whose party trick was to turn off the ignition while driving, let the engine run like that for a few seconds and then turn the ignition back on. The carburettor would carry on feeding fuel and air to the engine, even without a spark, and fuel would build up in the cylinder or exhaust manifold which would be ignited all at once when the spark was resumed. It was fun to do this when you were in front of a little old lady and watch her jump through the roof as your car emitted a loud bang - and maybe a tongue of flame from the exhaust pipe. I dread to think what it did to the engine, though...

[NY]

What causes a diesel to run lumpily (one, two, three, pause, one, two, three, pause) when first started from cold, and to emit aromatic pale blue smoke for a few seconds? My wife's old Honda Civic 1.7 diesel (2002 reg) used to do this towards the end of the time she had it. Was it a failed glow plug which meant that the engine was only running on three cylinders till the engine warmed up enough for fuel to detonate in the fourth cylinder?

It made no difference how long you left the key in the ignition position before starting the engine, and it only happened when the engine was cold and was worse when the ambient temperature was low.

[Clive George]

HDi has glow plugs too, they're just not as important as in the XUD. The wires to the injectors are low current ones, but there's also a fatter wire to the glow plugs which is chained one cylinder to the next further down the engine.

(I'm not sure if more recent HDis have permanent glow plugs as MrCheerful suggests - I know that mine, on the first generation 2.0 8v, are for cold starting only)

Priming pump, used for when you need to get fuel from the tank to the pump after eg running out of fuel or replacing the fuel lines. The BX version of the XUD had a little piston pump - push a button lots of times to prime it. I've done both of the examples mentioned :-)

It's not "branches to the injectors", it's in front of the high pressure mechanical pump. The low pressure bit goes into the pump, then four pipes come out of the pump off to the injectors. The pump is driven off the cam belt, and is a timed thing - when you replace the cam belt, the pump needs to be held in position just as the cam and the crank are.

On the HDi, the pump isn't timed, it's continuous. It sends higher pressure fuel to a branched pipe (yes, this engine does have them), with solenoid controlled injectors - that's common rail. The HDi also normally has a low pressure pump in the tank, so no need for priming, but occasional need for replacement - I've had one fail.

[Clive George]

One dead glow plug. The XUD would do that, especially in winter. It would start with two failed plugs and a lot of smoke. I'm not sure I ever was slack enough to get it to three failed.

[Fredxxx]

That depends on what you call the unit that controls the fuelling with a stepper motor.

YMMV

Yes it is an assumption too far. Only an idiot would contemplate such a diagnosis.

I'm not the one here questioning someone who has worked in the field of diesels when all their knowledge is based upon model airplane engines. I suggest you stick to them and leave real men's diesels to others.

[Fredxxx]

No I haven't. This whole thread was about a Landrover engine and moved on to agricultural engines without injection. If you want to mention aeromodelling shows, perhaps a new thread?

Is that "no" agreeing to me?

So no agricultural engine running on compression ignition without injection?

[Fredxxx]

If you regard an engine that is 10 years old school then I would agree with you.

[Fredxxx]

Generally I would agree with you. But presumptions can be dangerous.

[The Natural Philosopher]

So can believing in stories from the Daily Express, emanating from China.

Or indeed anywhere else.

Sure I read the express, but really, I don't actually BELIEVE what it says.

"REVEALED: The scientific PROOF that shows reincarnation is REAL"

[NY]

Ah I misunderstood what he said - I thought he was saying that the HDi didn't have them, but it's just that they aren't always needed and don't need to heat the cylinders as hot because the fuel droplets are smaller.

I presumed all diesels had a continuous pump to supply high pressure fuel to the four injectors, with the relevant one opening when its piston gets to the appropriate place near TDC. Do some diesels send pulses of fuel pressure at around the time that each injector opens.

Yes, I often hear that pump in the tank making a rapid chuntering sound when I first turn on the ignition after I've filled up with fuel.

[Clive George]

All common rail diesels are like that, and most modern diesels are common rail.

Mechanically pumped diesels, like the XUD, have one pump per cylinder, all wrapped up in the main diesel pump. The injector opens with the pressure of the fuel - it's not the pulses of fuel pressure being sent at the same time as the injector is opened, it's the pulses of fuel pressure which open the injector.

There are also ones with one little pump per cylinder at the cylinder end - VAG PD, and the TD5 mentioned.

If one day your car doesn't start, have a listen for that whirr when you first turn the key to ignition on. If it's not there, it's your fuel lift pump :-)

[bert]

As modern as a Ford Transit.

[bert]

No that's new. This is old

[The Natural Philosopher]

:-)

Them all tratters!

[NY]

Ah, I didn't realise it worked like that as recently as the XUD engine and therefore as recently as 1997 when I bought the 306 with XUD. Evidently right at the end of the life of that technology because it was all new HDi in my 1999 306.

I know the VW PD engine all too well :-( The only diesel engine that I have repeatedly stalled because it does what no other diesel does that I've ever driven - stalls if you don't apply quite enough accelerator (even more so than a petrol!). I test-drove one and had great difficulty whenever I set off because it stalled very suddenly (as if the ECU had turned off the fuel completely) if I let the clutch in slightly too quickly or didn't press the accelerator enough. And the salesman said almost everyone does that to begin with - which suggests a design fault rather than a lot of drivers who aren't used to it. A horrible engine. Put me off the Mark 5 (I think) Golf.

[Clive George]

XUD was introduced in the early 80s - apparently on the Horizon, though really made its mark in places like the BX, 205, 405, etc. It was probably the first really popular car diesel engine.

Later ones did have some electronic control on them, but the pump remained essentially mechanical.

[bert]

In article , NY writes

I assume then that you've never driven a Land Rover 300 TDi