Xantia 1.9TD reluctant to start when hot

Unread post by **Old-Guy** » 28 Oct 2008, 18:42

I've been living with this one ever since I bought the car 2½ years ago, more of an annoyance than a problem:

Provided I wait until the glow light goes out, cold starting has never been a problem. Third or fourth cylinder on compression fires and she bursts into life.

When the engine's not cold, even though I wait for the glow to go out, it always needs two brief cranks of 3 or 4 revolutions before it will start. If I don't crank - pause - crank, I can crank away for a lot longer before it eventually bursts into life with a great cloud of unburnt diesel. Very anti-social!

It's worst (needs a longer second crank) when the temp needle has moved off the stop a little way. A little throttle makes no difference (other than a bigger puff of unburnt diesel).

It's only done 88,000 which I hope is much too young for a rebuild to be necessary, but the only thing I can think of is a lack of hot compression because the valves need re-seating.

Am I missing something in the way of a fault or a special hot-start technique that's peculiar to these engines?

Any ideas would be most welcome

Cheers

Guy

jgra1 · Unread post by **jgra1** » 28 Oct 2008, 18:46

hi Guy, mine exaclty the same (now i have fixed glowplugs)

one turn of engine is all it needs on a cold morning

when hot, 3 or 4 turns

a common issue...

CitroJim had some ideas on this I think...

Sorry just re-read your post and it could almost be a valve clearance issue, but that may affect it when cold too..

uncle buck · Unread post by **uncle buck** » 29 Oct 2008, 09:39

I think most of the 1.9TD engines suffer the problem of having to crank them a bit when warm.

With the normally aspirated Diesel once its warm it will start without heater plugs at the first flick of the key....with my 1.9 TD you could drive 100 miles & turn the engine off for a few second & have to wait for the heater plugs before attempting to start the engine otherwise it would crank for what seemed like ages before starting.....I think it must be something to do with the compression ratio of the TD engine.

TBONE · Unread post by **TBONE** » 29 Oct 2008, 10:32

clean the EGR valve out it seems this has been the answer for a few people so worth a try

Unread post by **Old-Guy** » 29 Oct 2008, 10:34

Thanks guys

It bugs me that I can't work out why it starts hot after 2 cranks (let the key go and twist again), with a lot less cranking in total, than if I keeping cranking until it does start.

Not a fuel/injection problem (clouds of unburnt diesel).

All cylinders fairly even on compression (doesn't crank unevenly).

The battery doesn't noticeably fade, but maybe I'll have a go at the week-end at cleaning up the high-current path to see if I can improve the cranking speed a bit - even though it seems perfectly OK.

Unread post by **CitroJim** » 29 Oct 2008, 19:47

As soon as I have some time Guy, I'll go into a theory I have on why Bosch pumps take a bit more starting when hot. It's not a problem, just a feature...

lexi · Unread post by **lexi** » 29 Oct 2008, 23:26

May not be the problem but valve clearance can be a hot start issue.

Unread post by **CitroJim** » 30 Oct 2008, 08:53

This is my take on the issue.

The one thing that makes the Bosch pump veggy friendly is the design of the HP pumping element. It works basically on the same principle as a hyperdermic syringe and in diesel pump terms, runs wide clearances, hence why it can get away with pumping thick veg oil without seizing.

Every VP20 equipped car I've had has been a reluctant hot starter compared with when cold. Every car I've had with a Lucas pump starts instantly hot or cold. The Lucas has a very different design of HP pumping element and the tight clearances it runs is it's veg downfall.

I reckon the wide clearances in the Bosch cause a reduction in pumping efficiency when the pump is hot and the fuel is hot and thin. Also, the way the timing device works will initially see it set to the fully retarded position and it'll take a while longer when cold to reach full start advance, again due to reduced fuel pressure in a hot pump pumping hot diesel.

When everything is cold, clearances are tighter, fuel is thicker and it pumps that bit more effectively. As I say, just a theory. It may be complete rubbish.

Lexi, tight valve clearances bizarrely normally cause cold starting problems

A quirk of the XUD is the valve clearances are tightest when the engine is stone-cold and they open-up as the engine warms.

If you want good hot starting, get a Lucas

Xaccers · Unread post by **Xaccers** » 30 Oct 2008, 10:08

Think you could be right Jim, Cassy ran out of veg over the weekend so I put in some V-power.
Noticed at lunch when I got home, then had to head off to pick up a parcel a minute later she needed extra cranking to start.
Don't recall her needing that on veg though, will pop to costco and fill up and let you know

Unread post by **Old-Guy** » 30 Oct 2008, 20:06

Thanks for that insight, Jim. I can't flaw your logic.

But (sorry to harp on about this) I still don't understand why two short bursts of cranking always work (hot) but it takes much more cranking if I don't pause ever so briefly. I get the impression that it tends to start the instant I release the key.

Maybe I should conduct some properly controlled experiments to establish some reliable facts.

Could a mucky tank filter might be playing a part?
Thus: when the engine is running, the pump has enough 'suck' to pull fuel through the crud. When cold, thicker fuel means the pump generates more 'suck' (as per Jim's explanation). With two bursts of cranking, during the momentary pause residual suction pulls a bit more fuel through the mucky filter (and the battery voltage recovers slightly too), so that it starts promptly on the second burst.

After 13 years, but only 88,000 miles, on dino-diesel (no idea what was used for the first 10 years - I use Shell almost exclusively), would the collective experience out there suggest that the tank filter is likely to be a bit bunged up?

red_dwarfers · Unread post by **red_dwarfers** » 30 Oct 2008, 21:46

Theres no harm in checking the tank filter as a matter of course anyway but otherwise, what he said *points to Jim*

He's got the knowhow

Unread post by **CitroJim** » 31 Oct 2008, 07:49

Absolutely, it can be a shocker just how much can accumulate on the strainer, even when running on nothing but dino. Certain life-forms seem to find the water/diesel interface quite a convivial place to live and every diesel tank of a certain age will have a small amount of water on the bottom. These life-forms die on the strainer and clog it up.

Guy, going back to the hot starting issue, I've been giving it more thought as I do, at the strangest times, like when getting breakfast this morning

The Bosch is very reliant on there being a well-preserved vacuum in the fuel lines to keep the fuel level in the pump body high. Again, due to the design, the fuel level has to be maintained right to the very top of the pump body as the inlet to HP pump element filling passage, interrupted by the stop solenoid, is very high in the pump. Just a small fall in level will uncover it and admit air.

Fuel will only stay in the pump if the feed and esepcially, the return lines, are very air-tight. Again, when hot and thin, the diesel will more easily run back and lower the pump level. Those leakoff pipes have a guilty look. Even very tiny air leaks will be exaggerated when hot and the diesel thin. One run of the starter, a pause and another, gives the fuel a bit more time to pump and also reignites the glowplugs for a bit. Glowplugs, even when under post-heat, still go off when you are cranking and come back on again when you release the key. Also, it gives the timing device a bit longer to be pushed over and advance the injection timing.

So if the fuel level might fall when hot, why does it not affect cold starting in the same way? Good point. I'll have to go and do some more thinking.

jeremy · Unread post by **jeremy** » 31 Oct 2008, 08:26

How fast does the engine actually crank when hot? The compression of the hot engine will be higher than cold and its possible that the hot engine actually cranks slower than a cold one especially if the battery is past its best or too small.

You could try using jump leads and another vehicle when the engine is hot to prove the point.

I have a BX DTR Turbo (211,000 miles and a ZX 1.9D 103,000 miles) and I never have to heat the ZX when hot but generally have to heat the BX a bit but both start after about 1 turn then. Both have Lucas pumps.

Unread post by **Old-Guy** » 31 Oct 2008, 11:05

I think cranking speed and the battery is probably a red herring: it cranks at a good rate hot or cold and doesn't slow even after 5 or more seconds.

Jim, your explanation of the glow circuit's behaviour is a revelation (to me at least). I think you have put your finger on why two brief crankings works - I have a possible explanation of why cold starting isn't a problem.

One wet winter's evening in the early 70's, my TVR came to halt with fuel starvation. By the time I had found the torch, opened and propped the bonnet (the whole front end) there was plenty of fuel visible in the clear lines and the engine re-started immediately. A mile or so of giving it a bit of welly, we spluttered to a halt again. Went through the same performance. Drove home slowly with it missing up every hill. Not quite the impression I wanted to give my passenger (young attractive and female)

I eventually found the problem in daylight. Repeated running low had sucked up glass fibres from the bottom of the tank (not adequately sealed while it was being built into the tail). A plug of these fibres had built-up against the square shoulder of the lift-pump inlet. But by the time I had got the bonnet open, the plug had slid down the pipe out of sight! I sorted it properly with a replaceable filter (no shoulder on its inlet!) upstream of the pump, before the next young lady came along - we've now been married for 33 years

The point of this story is that it leads me to wonder if that, while the Xantia is parked overnight, gunge on the tank filter loosens/relaxes but is sucked into a tight mat during normal running so making the pump's job much harder?
Before anyone asks, the fuel filter has been changed recently without making any difference either way.
There's only one thing for it, take the car for a run and then take out the tank filter....
Is a hardwood drift and and gentle tapping the best way to loosen the locking ring? I'm worried about shattering aged plastic.
I'll let you all know what I find.

jgra1 · Unread post by **jgra1** » 31 Oct 2008, 11:47

hi Old guy

in my blog on here is a picture of my tank pick up

I had been running oil for a few months proir to Jim and I removing it

John