T90 Starting Problems

[chas]

My T90 has (relatively) suddenly developed starting problems. It has been behaving normally over the winter when I have run it up ashore but in the past couple of weeks has been much more difficult to start and, for the first few minutes when started, produces copious white smoke (I am pretty sure it is smoke, not steam). Can any of the engineers out there please tell me if these engines have some sort of fuel enrichment mechanism, and if so, how I can get at it? The glo plugs are working - or at least the ammeter discharge when I switch them on appears normal. I have filled the tank with diesel, well dosed with soltron and both fuel filters have been recently changed.

Thanks for any help.

 

[oldharry]

White smoke usually means fuel starvation, usually due to an air leak in the fuel lines, or a blocked filter. As you changed those that is unlikely, but far more likely one is not seating properly on its seal, and allowing an air leak. Clean all the fuel line joints and filter seals with a tissue, so that the tissue remains clean. Run the engine up for five or ten minutes, then go round again: any trace of diesel that was not there before signifies a tiny leak which will be admitting air to the fuel lines. Check every joint in the fuel system whether or not you disturbed it, as changing the filters may have been enough to crack a weak joint.

If that is not it (and I would be surprised if it is not) then you may have problems with the fuel lift pump diaphragm starting to fail.

If none of these then you need to get the injectors checked out. Did you disturb the injector pump timing when you were servicing it? All the bleed screws tight and sealing properly? Is the air inlet clear? (this usally causes black smoke, but not always.)

After that the problems get more serious - e.g. compression or Injector pump difficulties.

Good luck!

 

[colvic]

Hi Chas

had the T75 and it was a bit of a Bu**er to start after I'd changed the fuel filters. Turned out that I hadn't bled the system fully and a very very minor air leak was allowing the fuel to drain back from the injector pump.

Re-blead and check tightness of all unions.

Phil

 

[chas]

Thank you - I had not thought of that - I will have a go.

 

[chas]

Thanks - could well be. I had an awful job bleeding it during the winter and there could be a bubble or two.

 

[owen]

chas i also have had a similar problem. new g/plugs over winter and it starts worse than before. once it is warm it starts first time but from cold it needs a lot of turning over before it catches, and after starting it produces clouds of white smoke. i had presumed this was unburnt fuel from all the turning over but maybe not.cannot find any air leaks so am at a loss. hopefully there will be some more suggestions here.

 

[scottie]

check the glow plug
carbon build up round the glow plug apperture is a common problem
this can be cleared using a twist drill turned by hand
the carbon build up conduct the heat into the head rather than the air space round the heater plug

sorry cant remember drill size but it is the the sherpa work shop manual that covers the bmc 1500 engine

 

[chas]

scottie, thanks for this. Last time I tried to get the glo plugs out a couple broke and I ended up having to take the head off to clean up the mess. Any hints on how to get them out without breaking them?

 

[chas]

Exactly the problem I have. What mystifies me is that it has suddenly developed. Up until a couple of weeks ago, it was perfect.

 

[Anonymous]

The clouds of white smoke will be either steam or unburnt fuel. Is the engine running even and balanced, or rough with vibration? What happens when you rev it? Does the problem go away after starting - if so, after how long?

 

[chas]

Engine runs well when it eventually starts. Within a couple of minutes the smoke (I am fairly sure it is smoke) disappears and all is well and back to normal - engine ticks over nicely and responds well to the throttle - no smoke at all. Warm starting is almost instantaneous.

 

[oldharry]

Still sounds like an air leak to me. Or a couple of glow plugs gone down. Quick check disconnect them and put a meter on the terminals - should get around 1ohm resistance reading - possibly lower. Doesn' t entirely prove them as they may have shorted internally and without accurate gear you cannot tell, but at least it shows up open circuit ones where the element has failed.

 

[Anonymous]

Sounds to me as though one cylinder is low on compression. Have you taken it out for a good run at 80% throttle for an hour or so, this season? A good run might sort the problem out if the valves are not seating properly, the rings are sticky or the bore a bit glazed. If this is the case, what you don't want is lots of ticking-over while watching your navel, in the marina! EDIT: If that doesn't work, check the compression.

 

[owen]

Re: T90 Starting Problems re lemain

sorry to barge into this thread with my problems. my t90 starts as badly as chas's. it then runs perfectly and when warm will start immed.. it will rev in neutral up to 4000 and in gear to 2100.sounds like a g/plug problem to me but as i said they are brand new and the holes have been cleaned with the drill as recommended. any suggestions gratefully received

 

[Anonymous]

Re: T90 Starting Problems re lemain

Does yours push out lots of white smoke after stating, as well? Does the smoke smell of diesel or steam?

 

[chas]

Result??

Many thanks to all who responded. I tried Lemain's suggestion of a good long hard slog and it seems to have worked. Engine now starts better and, although there is a little white smoke when it fires, not nearly as much as before. Hope this will be of use to anyone else with a similar problem.