smoke

[DB6]

I have a slight problem with my '68 Jag 240. When accelerating to high revs, bluish smoke comes out. When the car is cold, it is completly black.
My mechanic simply told me off about me pushing the car too much after having had a laugh about having to rebuild the engine soon...

Please help. What could it all be due to?

danny

 

[piman]

Hello Danny,

Blue smoke is oil burning, which is not so good, you say the engine has been rebuilt? Older engines very oten draw in oil down the valve stems on the overun and this shows up as blue smoke when you accelerate again, but usually just for a short time.
Black smoke is too rich a mixture, does your Jaguar have Solex or S.U. carburettors? If it is the S.U. system with the auxiliarly starting carburettor it may be set too rich, and can be adjusted.

Alec

 

[DB6]

Alec,

No, my engine has never been rebuilt, and i don't really feel like doing so either! The car has very low milage and is in original condition (arround 36'000km). What could or should I do?

About the black smoke, it mostly happens when the car is cold, so could it have something to do with the choke?

danny

 

[DB6]

It has twin S.U. carbs.

danny

 

[piman]

Hello Danny,
sorry, I mis-read your post, I read it as having been rebuilt not needing to.

Jaguar engines of that era did tend to burn some oil and if your consumption is not excessive I wouldn't worry. (300 miles per pint say {1\2 litre}} It is worse if you drive the car hard, using a lot of revs.
The original 2.4's had Solex carburettors whilst the others had S.U.'s with an auxiliary starting carburettor which operated automatically. (I don't know if the 240 used the same system or had a manual choke).
Assuming yours is the same, there is a temperature switch at the front end of the water rail which mounts on the inlet manifold. This switch is closed when the engine is cold. When it is on there is a distinctive 'hiss' from the starting carburettor and it is possible that the thermal switch fails to open leaving the car running rich.
If it is switching off, then it probably needs to be adjusted. Looking at the auxiliarly carburettor , which is between the main ones, you will see the end of a small vertical needle, which protrudes through a nut. Screw this nut down to weaken the mixture.

Hope this helps, but if you need a more detailed description, e-mail me at jwb808c@btinternet.com.
I can send you a photo which makes it clearer.
P.S. If it is running rich on the aux carb, that will worsen your oil burning by washing oil off the cylinders.

Alec

[ 07-27-2003: Message edited by: piman ]</p>

 

[DB6]

Alec,

On the 240 it's a manual choke with two positions, but thanks for the advice. I does consume a considerable ammount of oil (+ some leak, which Im told is normal on such cars) Im starting to see a bit clearer now.

danny

 

[piman]

Hello Danny,

Yes, leaks are a part of older engines. Incidentally, early XK engines didn't have a rear crank seal so if you parked uphill, oil would leak out the back of teh engine.

Just a thought as to what oil you are using?, don't use modern light oils this will make the situation worse.

Alec.
Did I mention that I have a MK 2 also.?

[ 07-28-2003: Message edited by: piman ]</p>

 

[DB6]

The oil is ok.
No, you hadn't mentioned your ownership of a Mk II. I think it is a great car. Timless design.

thanks for all your advice alec!

danny