White exhaust, with a hint of blue

[fiddle]

Its a Thornycroft t90. Thought Id have the injectors serviced before I lifted the boat this year. The man said they tested OK and to leave them alone in future unless I had BLACK smoke.

Put them back, bled it. Sounds OK. But what a fog.

It was so much WHITE smoke (with the merest hint of blue) that I cut the engine after just a few miutes, thinking something was drastically wrong. It looked like Id just put some REDEX in a 1974 Ford Escort. (ah youth!)

I took the injectors out again to have them double checked cos the book said a sticking nozzle could be the problem. Could it be anything else? Everything was fine before the first removal

If the man double checks and still says they are good, I shall put them back. If I run the engine for longer to see if the smoke clears, will it do much harm!

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[brianrunyard]

According to the fault diagnosis section of the Perkins Prima manual:
Blue or white exhaust smoke, First checks:
1. Wrong grade of lubricationg oil
2. Fault in cold start system
3. Engine temperature too low

If these are ok, things get a little more serious:
4. Timing of fuel injection pump incorrect
5. Valve timing incorrect
6. Bad compression
7. Cylinder head gasket leak
8. Worn cylinder bores
9. Piston rings not free or damaged
10. Valve stems or guides worn
11. Piston damaged
12. Valve stem seal damaged

Hope it's one of the easy ones,
Regards,
Brian

<hr width=100% size=1>Brian
http://homepage.ntlworld.com/brunyard

 

[vyv_cox]

I have always considered copious white smoke to be unburned fuel due to an injector problem.

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[ex-Gladys]

...water in the combustion chamber is a regular cause...

<hr width=100% size=1>Larry Botheras

Essex

 

[vyv_cox]

Indeed it is, especially if you own a Bukh. In the context of this thread it would appear to be irrelevant. And it depends what you mean by copious.

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[Gordonmc]

This is the blurb from the T90/T108 manual:
Excessive white smoke - Injection timing incorrect; poor compression; water in the cylinders.
Excessive black smoke - insufficient coolant; faulty injector(s) inj. pump maximum stop screw out of adjustment.
Excessive blue smoke - Engine needs top overhaul; worn piston rings and bores; faulty injectors.

Assuming there was no excessive smoke before the service it looks as though the problem is down to the injectors of injector timing.

My T90 gives out white smoke on start-up and clears after maybe five minutes. The longer the engine has been unused, the more smoke I get. Was there a particular reason you decided to get the injectors serviced?

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[colvic]

Did you make sure the little packing washers were under the injectors when you refittef them? Where do you live, for there are a couple of "BRILLIANT" engineers just outside cambridge who kknow the Thornycroft range inside out.

Phil

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[summerwind]

As the only thing that has been changed since running OK is the removal and replacement of the injectors, this is where to look.

Were the copper washers replaced under the injectors? its usually best to either fit new washers or anneal the old ones to soften them up so that they give a good seal. Poor seal = low compression = white smoke.

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[brianhumber]

from your description suggest either:
water in cylinders being turned into water vapour but this would result in white vapour or
poor combustion due to cold and old worn engine resulting in white/blue smelly smoke.

Most pre-90s diesels will emit white smoke if started cold especially when worn. Remember the old BR dmu railcars rattling away for hours in stations and then emitting plumes of white/blue when starting away, or old coaches/lorries being started on a frosty morning.

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[Guest]

with all due to respect to all the other posters, we have had everything guessed at but no thought.
was it smoking like this before you took injectors out? if not it is down to one thing and one thing only, the injectors.
if the injector washers are faulty you will know about it, there will be a horrible noise coming from the injectors where the gas is by passing them.
timing? since when did removing the injectors from a thorney croft change the timing?
water in the cylinders? where from? and continuously by the sound of it.
i suspect that your injector man has made a horlicks of setting the injectors and is now wriggling, if he has set the breaking pressures too low or the nozzles are goosed the symptoms will be just as you describe.
from him who used to get a slap round the head from the chief fitter if he didnt set em right
stu



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[saturn]

you say you ran the engine for a few mins, if i were you i would run the engine for longer to get it up to working temp to see if it clears, or maybe one of the injector lines still needs bleeding after that get the injectors rechecked(if all was well before).

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[Heckler]

once you have fuel to the pump and it has started injecting and the engine has started it will in effect "bleed" itself, if it will start you dont need to bleed all the injectors.
s

<hr width=100% size=1>http://www.beneteau-owners-association.org.uk

 

[saturn]

well i disagree with you,what you say may be true most of the time but not always and that would be the first job i would do in regard to the post.

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[PeteMcK]

Thornycroft smoke

It's so long since I pulled mine (10 years) I can't remember whether the sealing washer down at the nozzle face is flat copper (I think it is) or corrugated like in old Landrover diesels. Change them every time (get them posted from Thornycroft in Preston to be sure; get some spares too); the corrugated type especially is a one shot seal. If there's a leak there, you'll get incomplete - or no - combustion, lots of blue smoke and a bit of a racket from the leak. Fish the old seals out with a bit of threaded bar and chuck them away, make sure the seats are scrupiously cleaned (a spot of RedEx will soften any deposits) and fit new seals. DO THIS FIRST IF YOU'RE IN ANY DOUBT.
I take it you were careful to make sure no dirt got into the fuel ports.
I'm not surprised the break pressures were ok as the units are very reliable but if in doubt, have them checked. Dismantling and overhaul to "as new" performance at a Lucas Service depot - LSUK now - should cost about £20 each (one in just about every large town or city).
Retarded pump timing would give similar symptoms but if you haven't touched, it shouldn't have changed.
Did you have to crank and bleed a lot before the engine fired: you might simply have coated the exhaust with fuel and it has to be evaporated and/or burned off - it might clear itself in a few minutes.
One slightly dodgy seal, nozzle or pressure setting can result in vast amounts of light blue smoke.
Once the engines's running, the injectors tend to self bleed and in fact I usually simply fire up the easiest cylinder to get at: the others follow within a couple of seconds. But don't depend on it especially if they've been drained. I think the handbook says to bleed all 4 and this may be neccessary depending on the type of restrictor fitted on the return line to the tank.
LEAKS/TIMING/INJECTOR SETTINGS/AIR - any one of these will almost certainly give a rough idle, a regular misfire, but possibly irregular if it's the timing. Incorrect timing would also make starting difficult. If it's running smoothly, I doubt whether it's anything other than fuel needing burned off.
And now that you've been chucking unburnt fuel down the exhaust, no matter what, it's going to take a few minutes to clear now anyway. It won't do any damage to run it as long as you're sensible, i.e., don't go using the boat until you rectify it: you could, for example, scorch a nozzle seat with use at high load if there's a leak.

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