Xantia TD Hot Start Woes

Brian UK · Post by **Brian UK** » 06 Jul 2007, 17:27

jeremy wrote:The 1.5 is a different engine and I think operates its valves through rockers. The arrangement of the rockers could possibly cause the opposite effect.

No the 1.5 most certainly has an overhead cam acting directly on the valve caps, exactly as the 1.9 XUD.
The adjustment of the clearances is done with shims, also the same.
Hot starting problems on the 1.5TUD are not uncommon, and are often due to the clearances closing when hot. I didn't believe it when it was suggested for the problems I was having, but re-adjustment certainly cured the hot start problem, so I was convinced.
Oh, and the engine always started perfectly when cold.

AndersDK · Post by **AndersDK** » 06 Jul 2007, 19:59

Sorry to butt in here with my ignorance -
But the general consensus is then that the valve clearances DEcreases over time on overhead cam engines - not just diesels ?

- because the valves wear down into their seats ?
- despite normal build up of carbon on the seats ?

Post by **CitroJim** » 06 Jul 2007, 20:19

AndersDK wrote:Sorry to butt in here with my ignorance -
But the general consensus is then that the valve clearances DEcreases over time on overhead cam engines - not just diesels ?

- because the valves wear down into their seats ?
- despite normal build up of carbon on the seats ?

As I understand and believe it Anders, the seats sink into the softer alloy over time through constant hammering of the valves against their seats. Petrol XUs don't seem to suffer as badly because perhaps the diesels have stronger valve springs or faster accelerating/decelerating ("hotter") cam profiles . The latter may be the case as due to the high compression ratio of a diesel and the lack of space in the combustion chamber, they run sub-optimal valve timing (i.e. it would be nice to keep the valves open longer but there is not enough room to do it) so to compensate they may run more agressive profiles. This may explain why the 1.8 NA XUD suffers worse from this than the 1.9 TD XUD as in theory at least, the NA engine will have a hotter cam profile than the TD.

All pure speculation on my part Anders, the bit about cam profiles and heavy springs. I reshimmed Dad's 205D (1.8NA XUD) because it refused to start in cold weather and all four inlets had closed up to the point of negative clearance. Just a touch of heat and the differential expansion of the steel valve train and alloy head provided just enough clearance for the engine to run normally. Inlets close up more because they have a lesser clearance to begin with.

So, on an XUD, valve clearances should, in theory at least, increase with heat and thus may not be the root cause of poor hot starting. However, the clearances have got to be worth checking just to eliminate them from enquiries.

AndersDK · Post by **AndersDK** » 06 Jul 2007, 20:31

Thanks Jim -

Donno from where you've got it. Either you've had your head inside 1000's of engines - or you were born with a silver spanner in your hand

I've had some strange problems with an XUD experiencing hot start problems where "everything seems in perfect condition".
Thing is - I checked the valve clearance going by the book - i.e waiting with the engine over night to cool off.
Doing it this way you may get sensible (not suspective at least) readings, albeit to the low side.
That could certainly be a pointer to the problem.

I wonder if this problem could pop up rather suddenly as the clearance on one valve finally disappears on a critical hot day ?

nexarius · Post by **nexarius** » 07 Jul 2007, 18:30

Yay!

Changed the starter motor today, and the engine turns over seriously faster.

I guess the old one must have just worn out with age. Judging by the peeled paint and rust, I reckon it was very hot for a long time. Maybe just bad design putting the starter motor somewhere that gets too hot?

Fingers crossed, but I hope this will solve the problems. I have some leakoff pipe so I can change them anyway, just for the hell of it!

Hopefully I'll get a chance to run the engine up to temperature soon and see how it behaves then. I need to change a cooling fan and an engine mount first though (it's still on axle stands in the garage).

Thanks for your help so far guys!

Matt

Jolly Jack · Post by **Jolly Jack** » 09 Jul 2007, 21:33

Hi
I havnt been on this forum for years and was just browsing to find info on engine mountings when I came across this thread. Its probably not the same but I had a BX 1.7td something that would not start with a hot engine. it turned out to be the fuel solenoid on the hp pump. I think the coil was going high resistance when it was hot. Changing the coil sorted it ok.
John

nexarius · Post by **nexarius** » 12 Jul 2007, 22:31

Just got in from changing the bottom engine mount (stabiliser bush).

Crikey.

It was a cow of a job. Got the old one out quite easily with the aid of a hacksaw, but the new one was NOT happy about going in!

Froze the new one and tried to coax it in with clamps and a hammer. Nuh-uh. Didn't even begin to go into the hole.

Ended up with my dad helping me to fabricate a bolt puller thing using an old bicycle axle and bits of steel for end plates.

And a big hammer.

In the end it was 45 degrees out, and sticking about half a centimeter out of the alloy cast, at the point we stopped trying!

Now just the fan left to replace. Anyone got any tips on replacing a cooling fan on a 1.9TD with air con?

Post by **admiral51** » 12 Jul 2007, 23:05

not done one on a td but had lots of fun with my 1.9 a/c
to get really good access from front i had front grill and bumper off i also took slam panel out as i was replacing complete unit ie 2 fams and housing
if you do bumper and grill and lift slam panel up onto engine bay you dont remove any lock mechanism for bonnet
radiator will unclip and tilt forward good time to clear leaves dirt etc from gap
a/c condensor is sat inside fan housing with rubber bushes on r/h as you look in dont think you will get behind fans without removing everything.

with slam panel out fan housing will be a little bit loose from top

bolts holding fan to housing are 10mm very awkward to get at and are behind fans ie a/c condensor side to undo
the wiring plug is about 9 oclock as you look at fans and are a very snug fit

it is easier without the blade on to get to bolts etc but if you try to take the blade off go careful as the screw/bolt is LEFTHAND THREAD

will try to get pics of my old housing fans etc put on tomorrow

hope this helps

colin

Post by **admiral51** » 13 Jul 2007, 19:23

put some on here not sure how it will turn out first time for everything

http://profile.imageshack.us/user/admiral51/

colin

lolingram · Post by **lolingram** » 14 Jul 2007, 15:22

This has been my **experience** on 205D Pugs...

As far as slow hot starting is concerend, it has been the case to a greater or lesser extent on all the mechanical inj. XUDs I have owned to date. Cold starting always within a turn of the starter, so it can only be a fuel problem, possibly minimal vapourisation?

None of the HDIs suffer at all, always starting instantaneously Of course these employ tank electric pumps...

..I reshimmed Dad's 205D (1.8NA XUD) because it refused to start in cold weather and all four **inlets had closed** up to the point of negative clearance. Just a touch of heat and the differential expansion of the steel valve train and alloy head provided just enough clearance for the engine to run normally. Inlets close up more because they have a lesser clearance to begin with.

MikeT · Post by **MikeT** » 14 Jul 2007, 16:28

I only have a few months experience of this one mechanically fed XUD and, after replacing the leak-off pipes, hot-starting is as instant as cold starting... providing the glow plug light has gone out first.

Additionally, I've learnt that cranking rpm is far more critical with diesel engines as they require high air compression/temperatures to ignite the fuel.

p.s. Sorry, didn't mean that to appear confrontational

lolingram · Post by **lolingram** » 14 Jul 2007, 17:07

I wonder if some air can get back in through porous leak-off pipes?

after replacing the leak-off pipes, hot-starting is as instant as cold starting... providing the glow plug light has gone out first.

lolingram · Post by **lolingram** » 14 Jul 2007, 17:30

According to Riccardo, the limit on aggressive valve timing on diesels is simply that one cannot open the inlet valve very early due to piston clearance, and closing it late simply pumps back out valuable compression ignition gas at cranking speeds. The situation with supercharging is not quite so bad as the compression ratios are a little lower.

The latter may be the case as due to the high compression ratio of a diesel and the lack of space in the combustion chamber, they run sub-optimal valve timing (i.e. it would be nice to keep the valves open longer but there is not enough room to do it

MikeT · Post by **MikeT** » 14 Jul 2007, 17:36

lolingram wrote:I wonder if some air can get back in through porous leak-off pipes?
after replacing the leak-off pipes, hot-starting is as instant as cold starting... providing the glow plug light has gone out first.

I saw lots of air bubbles in the fuel pump feed before they were changed and now I cannot see any and the car starts fine when hot. If they are leaking slightly still, it's not affecting the hot start at all. Do they make porous leakoff pipes?

lolingram · Post by **lolingram** » 14 Jul 2007, 19:36

No, you have to order them specially made...

Do they make porous leakoff pipes?