BMC 1.5 Burning engine oil

[Serendipity]

Full throttle starting on a cold engine is a sure way to bust a ring or two!!!

 

Exract from BMC Tempest manual:-

 

2. Turn on fuel supply and set the throttle in the fully open position.

3. Turn key..............immediately the engine fires release key and close throttle.

[John Orentas]

Full throttle starting on a cold engine is a sure way to bust a ring or two!!!

 

 

Don't want to sound pedantic but a diesel engine always starts on full throttle, only when the pre-set speed is detected does it regulate itself and stabilise.

[DieselDuck]

Don't want to sound pedantic but a diesel engine always starts on full throttle, only when the pre-set speed is detected does it regulate itself and stabilise.

 

I think you mean `Maximum fuelling`. Rotary & Jerk Pumps stop in the max. fuel position

ready for the next start, this has no connection with throttle position. As the engine starts the

hydraulic or pnuematic governor takes over to reduce speed to where the throttle has been

set or to idle. Very basically the throttle restricts the governor to the desired speed, it then

adjusts fuelling for varying load as necessary keeping the same revs.

 

As to the manual extract, OK, but I feel that it does indicate that although you start with full

throttle, it says close throttle when engine fires, which means to me that the engine should

not be allowed to let the rev`s climb to Max. No Load Speed untill you close the throttle!

[John Orentas]

I think you mean `Maximum fuelling`.

 

 

It was yourself who used the term 'Throttle', I am always reluctant to use it in connection with diesels, carburettors have 'throttles'.

 

P.s. ever noticed how many ways there are to spell 'carburettor'.

[DieselDuck]

Don't want to sound pedantic but a diesel engine always starts on full throttle

 

Exract from BMC Tempest manual:-

 

2. Turn on fuel supply and set the throttle in the fully open position.

3. Turn key..............immediately the engine fires release key and close throttle.

 

Seems the manufacturer is happy to use this generic term as a good indicator for the gadget

that makes it go faster (do you `electrolux` your carpet).

[Serendipity]

Since this thread started, my BMC has started smoking big time - and I can pinpoint when it commenced to last weekend when I started it as usual momentarily on full throttle, and it sent out enough smoke in the second it takes to knock the throttle back, to hide my position in the marina. Here are the symptoms i've observed in the four hours running time since:

• Tickover - usual gentle blue smoke i've allways seen.
  
• up to 1800, more smoke than i'm used to seeing sometimes - if knocked back to idle and gently increased again, then it reverts to what i've seen in the past (moderate blue smoke).
  
• 2200 revs alarming clouds of blue smoke.
  

Oil pressure 20psi idle, just under 40psi fast idle onward (no discernable change).

 

This seems too much smoke to me to be a breather issue (is it?), and since it has come on suddenly is it more likely to be a broken ring? The variability of the symptoms in the mid rev range puzzles.

Julian

 

 

BTW - If i take the breather tube off the air filter then run the engine, what would I expect to see at the tube outlet?

Edited June 14, 2007 by Serendipity

[DieselDuck]

On a reasonably healthy engine, you should feel a SLIGHT rythmic chuffing from the breather pipe

with maybe a SLIGHT mist of blue smoke, (steam may be evident slightly as engine warms), rising to

a SMALL amount of continuous pressure as rev`s increase. NO chuffing or pressure would indicate

a blocked breather, probably where the hose come out of the engine, (oil separator), and any more

pressure than above would mean excess crankcase pressure, (pistons, rings or bores). If you do let

the engine rev to full throttle, (layman`s term), from cold at start-up, as I have said, you may have

suffered a broken ring(s).

Another give-away for a blocked breather is oil seeping from gaskets/seals all over the engine, as even

a small amount of pressure has to get out somewhere.

[Serendipity]

On a reasonably healthy engine, you should feel a SLIGHT rythmic chuffing from the breather pipe

with maybe a SLIGHT mist of blue smoke, (steam may be evident slightly as engine warms), rising to

a SMALL amount of continuous pressure as rev`s increase. NO chuffing or pressure would indicate

a blocked breather, probably where the hose come out of the engine, (oil separator), and any more

pressure than above would mean excess crankcase pressure, (pistons, rings or bores). If you do let

the engine rev to full throttle, (layman`s term), from cold at start-up, as I have said, you may have

suffered a broken ring(s).

Another give-away for a blocked breather is oil seeping from gaskets/seals all over the engine, as even

a small amount of pressure has to get out somewhere.

 

Thanks - I'll check that out tomorrow.

[Serendipity]

Right - got to the bottom of it this weekend, and this is what I found.

 

Fired her up, and not too smokey. Left the marina, but after half an hours cruise i'm leaving a thick plume of smoke which can only be described as embarrassing.

 

Moor up, and remove breather tube from the air filter, and find it's full of oil (the tube drops a liitle before it re-connects with the air filter and so forms a sort of 'u' bend effect, so the gasses must be condensing here). Removed tube completely and drained the oil out, put it back on the crankcase end only, and fired up. No excess gasses coming from the breather tube, and no smokey exhaust either.

 

So, reconnect breather, and everything is fine, and remained so throughout the weekend.

 

Quite why it should have started to behave in this way, or why it's worse when warmed up i'm not sure, but it does seem to explain why it's sometime worse than others.

 

If (when) it recurs, I shall definitely buy some longer tube and follow Tony's advice of terminating it in a container.

 

Julian

[Tony Brooks]

Right - got to the bottom of it this weekend, and this is what I found.

 

Fired her up, and not too smokey. Left the marina, but after half an hours cruise i'm leaving a thick plume of smoke which can only be described as embarrassing.

 

Moor up, and remove breather tube from the air filter, and find it's full of oil (the tube drops a liitle before it re-connects with the air filter and so forms a sort of 'u' bend effect, so the gasses must be condensing here). Removed tube completely and drained the oil out, put it back on the crankcase end only, and fired up. No excess gasses coming from the breather tube, and no smokey exhaust either.

 

So, reconnect breather, and everything is fine, and remained so throughout the weekend.

 

Quite why it should have started to behave in this way, or why it's worse when warmed up i'm not sure, but it does seem to explain why it's sometime worse than others.

 

If (when) it recurs, I shall definitely buy some longer tube and follow Tony's advice of terminating it in a container.

 

Julian

 

The oil mist separator on the original 1.5s was all but non-existent so if the side cover that the breather hose is attached to is flat, like the other one, think about fitting one from a later model, a 1.8, or investigate late MGBs which I think had a proper mist trap, but you may not be able to fit it under the manifolds.

 

AS the pistons get worn more pressure leaks past the rings an has to exit via the breather. If the mist separator is not very good the oil mist gets blown into the hose and builds up into what you have found. It is really just another manifestation of BMC Factory fitted oil leaks and not too much to worry about whilst the engine is starting easily (otherwise if could be so worn you had lost compression).

 

Tony Brooks

[Serendipity]

The oil mist separator on the original 1.5s was all but non-existent so if the side cover that the breather hose is attached to is flat, like the other one, think about fitting one from a later model, a 1.8, or investigate late MGBs which I think had a proper mist trap, but you may not be able to fit it under the manifolds.

 

AS the pistons get worn more pressure leaks past the rings an has to exit via the breather. If the mist separator is not very good the oil mist gets blown into the hose and builds up into what you have found. It is really just another manifestation of BMC Factory fitted oil leaks and not too much to worry about whilst the engine is starting easily (otherwise if could be so worn you had lost compression).

 

Tony Brooks

 

 

Thanks Tony - think I'll just go for the container option.

 

As for starting easily, i've allways had to use glow in the summer (second season of ownership), though the manual says should only be necessary in cold conditions. It won't fire with less than ten seconds glow at this time of year, so is that a BMC starting easily do you reckon, or is it excessive 'help'?

 

Julian

[David Schweizer]

Nothing to do with smoking, but about oil loss. The older BMC 1.5 engines do not have an oil seal on the gearbox end of the crankshaft, and rely on friction fit and the speed of the shaft to throw off any surplus oil. As the engine gets older, the fit loosens and oil will find it way into the bell housing. the standard way to allow this oil to escape is apparently to drill a hole in the bottom of the Bell housing and allow the oil to drop into the engine tray.

[Tony Brooks]

Nothing to do with smoking, but about oil loss. The older BMC 1.5 engines do not have an oil seal on the gearbox end of the crankshaft, and rely on friction fit and the speed of the shaft to throw off any surplus oil. As the engine gets older, the fit loosens and oil will find it way into the bell housing. the standard way to allow this oil to escape is apparently to drill a hole in the bottom of the Bell housing and allow the oil to drop into the engine tray.

 

 

I am not sure this is 100% true. I think the automotive version used a lip seal and the industrial version used a scroll and oil thrower. The only reasons for a scroll and oil thrower to leak is if the engine is installed at too great a down angle or if the sump is overfilled. I suppose if the thrower drain hole is blocked it would leak, but if the oil has been changed regularly I do not think it will block.

 

 

To Serendipity

 

It should start without glowplugs at this time of year, but I am not surprised if it does not. As long as it starts reliably winter and summer put it out of your mind and just enjoy the boat.

 

The 1.5 uses pintaux injectors that have a small "sideways" spray that mainly works during cranking. This puts fuel at the hotest part of the combustion chamber so it ignites faster. Yours may be blocked, but its not worth worrying about until other symptoms mean you have the injectors out.

 

Tony Brooks

[Theo]

Nothing to do with smoking, but about oil loss. The older BMC 1.5 engines do not have an oil seal on the gearbox end of the crankshaft, and rely on friction fit and the speed of the shaft to throw off any surplus oil. As the engine gets older, the fit loosens and oil will find it way into the bell housing. the standard way to allow this oil to escape is apparently to drill a hole in the bottom of the Bell housing and allow the oil to drop into the engine tray.

 

That sounds like mine!

 

I have been too busy to get to Theodora to do anything other than pump out the hold after the thunderstorms. I am suffering from withdrawal symptoms!

 

Nick