BMC 2.2 Intermittant blue smoke?

[Quattrodave]

Evening all,

 

BMC 2.2 diesel engine has intermittent puffs of blue smoke, not talking about cold but when really nice and warm, running for a couple of hours.  It feels a little strange to me as it's not constant & it seems to happen more at lower revs, less than 1800 ish.

 

I'm assuming it oil burning (blue smoke), compression is good and pretty even between the cylinders, it starts well, even from cold, 10 secs of heat & turn turn fire and runs smooth immediately, so I'm assuming the rings are ok.  I've checked the breather it's clear. My only other thought is valve stem oil seals, I'm sure if read somewhere only required on inlet valves.

 

Anyway, what do you guys think, is it more likely to be oil burning, whats the most likely suspect?

[StephenA]

Something like this?

 

 

[Tony Brooks]

27 minutes ago, Quattrodave said:

Evening all,

 

BMC 2.2 diesel engine has intermittent puffs of blue smoke, not talking about cold but when really nice and warm, running for a couple of hours.  It feels a little strange to me as it's not constant & it seems to happen more at lower revs, less than 1800 ish.

 

I'm assuming it oil burning (blue smoke), compression is good and pretty even between the cylinders, it starts well, even from cold, 10 secs of heat & turn turn fire and runs smooth immediately, so I'm assuming the rings are ok.  I've checked the breather it's clear. My only other thought is valve stem oil seals, I'm sure if read somewhere only required on inlet valves.

 

Anyway, what do you guys think, is it more likely to be oil burning, whats the most likely suspect?

 

Oil burning should be fairly constant unless globs of oil are coming down the breather, so I would tend to go for a faulty injector needle, when were the injectors last overhauled? Reading smoke colour is more difficult than some texts make out, your blue could be a sort of grey.

 

Unless you have a very early 2.2. with a pneumatically governed inline injection pump, there is no throttle to create much of a depression in the inlet manifold to suck oil down the inlet guides, so I tend to think valve seals are a less likely cause. If it created blue smoke after every start, then they could be implicated because oil may have run down when the engine was stationary, but not at odd times when it is running.

[Quattrodave]

57 minutes ago, Tony Brooks said:

I would tend to go for a faulty injector needle, when were the injectors last overhauled?

 

That's a good shout I didn't think about injectors.  I've never had these ones overhauled, I'll pop them out and get them sent off at some stage soon.

[Tony Brooks]

For clarity, on some engines it could be excess backlash in the timing gear, but as the 2.2. uses a triple chain and the tensioner is a proper sprocket, rather than a rubber pad, I think this is very unlikely.