How would you interpret this?

[wandering]

Hi there, 

 

I have a BMC 1.5.
 

Upon start, there is normally a cloud of white smoke which I’ve come to learn is quite normal. 
 

Sometimes however the engine exhaust will smoke but I am unable to ascertain why this might be. 
 

I took two videos. One just at the beginning of my journey so about 20 minutes in and another video about an hour and 15 minutes later. I didn’t change my speed and the conditions were the same throughout but the difference in smoke is confusing me. Maybe this is normal and I am overthinking it? Any clues here. 

Sometimes the smoke appears white as it leaves the exhaust but slightly blue as it goes about the air. Other times, it isn’t even there. 
 

smoke:

 

no smoke:

 

 

[Troyboy]

Far more knowledgeable members will be along shortly but my guess would be that you run your engine at tick over when moored up to charge your batteries / provide hot water which results in a build up of unburnt fuel /oil in your exhaust . When you set off and the engine is under load  the unburnt fuel / oil burns off causing the smoking for a while . Once the engine gets nice and hot the smoke disappears having burnt away all the residue from tick over running. Diesel engines like to be worked hard not run on tick over or slightly above tick over for hours . As I stated just my guess as a fellow BMC 1.5 owner for many years. 

[Tony Brooks]

1 hour ago, Troyboy said:

Far more knowledgeable members will be along shortly but my guess would be that you run your engine at tick over when moored up to charge your batteries / provide hot water which results in a build up of unburnt fuel /oil in your exhaust . When you set off and the engine is under load  the unburnt fuel / oil burns off causing the smoking for a while . Once the engine gets nice and hot the smoke disappears having burnt away all the residue from tick over running. Diesel engines like to be worked hard not run on tick over or slightly above tick over for hours . As I stated just my guess as a fellow BMC 1.5 owner for many years. 

 

A perfectly reasonable explanation in the absence of more info.

 

Question, when were the injectors last overhauled? Asked in case there is an intermittent sticking needle

[wandering]

2 hours ago, Troyboy said:

Far more knowledgeable members will be along shortly but my guess would be that you run your engine at tick over when moored up to charge your batteries / provide hot water which results in a build up of unburnt fuel /oil in your exhaust . When you set off and the engine is under load  the unburnt fuel / oil burns off causing the smoking for a while . Once the engine gets nice and hot the smoke disappears having burnt away all the residue from tick over running. Diesel engines like to be worked hard not run on tick over or slightly above tick over for hours . As I stated just my guess as a fellow BMC 1.5 owner for many years. 

No I don’t run the engine in idle but I do go quite slowly. Although, the past week I have been cruising daily. Those videos were on the River Trent. 

1 hour ago, Tony Brooks said:

 

A perfectly reasonable explanation in the absence of more info.

 

Question, when were the injectors last overhauled? Asked in case there is an intermittent sticking needle

They were refurbished 7 months ago. 

[Tony Brooks]

12 minutes ago, wandering said:

No I don’t run the engine in idle but I do go quite slowly. Although, the past week I have been cruising daily. Those videos were on the River Trent. 

They were refurbished 7 months ago. 

 

Thanks, in that case, although not impossible, a sicking needle is unlikely, as is one or more blocked axillary spray holes - a special hole in the injector to aid cold starting.

 

I would be happier with bluish smoke because that is less likely to be steam, but smoke reading is not as easy as the books make out.

 

How long do you hold the heater plugs on before starting?

How long before it actually starts?

Make sure all the glow plugs are working.

 

If the glow plugs have not been out for a fair while, it may pay to take them out and decarbonise the holes. Worry the plugs out by warming the engine, tightening a plug a bit of a turn and the undoing it that plus a little more, keep doing that until they become free, but you might snap a tip off. Use a 7/64" drill to clear the carbon.

 

Otherwise, as long as it eventually clears, just accept it is a BMC doing what BMCs tend to do,

.

Edited August 16, 2023 by Tony Brooks

[Tracy D'arth]

11 minutes ago, Tony Brooks said:

 

Thanks, in that case, although not impossible, a sicking needle is unlikely, as is one or more blocked axillary spray holes - a special hole in the injector to aid cold starting.

 

I would be happier with bluish smoke because that is less likely to be steam, but smoke reading is not as easy as the books make out.

 

How long do you hold the heater plugs on before starting?

How long before it actually starts?

Make sure all the glow plugs are working.

 

If the glow plugs have not been out for a fair while, it may pay to take them out and decarbonise the holes. Worry the plugs out by warming the engine, tightening a plug a bit of a turn and the undoing it that plus a little more, keep doing that until they become free, but you might snap a tip off. Use a 7/64" drill to clear the carbon.

 

Otherwise, as long as it eventually clears, just accept it is a BMC doing what BMCs tend to do,

.

11/64" drill for carbon clearing and it needs to be long series, like 5".

[Tony Brooks]

9 minutes ago, Tracy D'arth said:

11/64" drill for carbon clearing and it needs to be long series, like 5".

 

Thanks, I am always getting that wrong - as you have probably noticed. I fear the brain is getting too old to remember.

[wandering]

48 minutes ago, Tony Brooks said:

 

Thanks, in that case, although not impossible, a sicking needle is unlikely, as is one or more blocked axillary spray holes - a special hole in the injector to aid cold starting.

 

I would be happier with bluish smoke because that is less likely to be steam, but smoke reading is not as easy as the books make out.

 

How long do you hold the heater plugs on before starting?

How long before it actually starts?

Make sure all the glow plugs are working.

 

If the glow plugs have not been out for a fair while, it may pay to take them out and decarbonise the holes. Worry the plugs out by warming the engine, tightening a plug a bit of a turn and the undoing it that plus a little more, keep doing that until they become free, but you might snap a tip off. Use a 7/64" drill to clear the carbon.

 

Otherwise, as long as it eventually clears, just accept it is a BMC doing what BMCs tend to do,

.

How long do I hold the heater plugs before starting? Not sure I understand the question. Is that turning the ignition key half way before to full ignition?

 

Once I turn the key, the engine will start after about 5 seconds. After 5 seconds or so it’s a rush of sound, black smoke followed swiftly by a larger cloud of white smoke then I slowly and smoothly take my hand of the key. 
 

It does clear and then sort of comes back for a bit then clear almost as if by random. 

Edited August 16, 2023 by wandering

[Tracy D'arth]

28 minutes ago, Tony Brooks said:

 

Thanks, I am always getting that wrong - as you have probably noticed. I fear the brain is getting too old to remember.

I would swap you Tony.

[Tony Brooks]

6 minutes ago, Tracy D'arth said:

I would swap you Tony.

I understand why that is, but I think so far I would rather not do that swap.