BMC Engine Problem

[jacksonp_uk]

Hi any engine experts out there

 

I recently did a top end overhaul on my BMC 1.5 diesel engine. This was primarily to overcome a serious oil burning problem which developed over a 7 day cruise in late summer. I identified this as most likely being the seals on the valve stems failing. On strip down these seals had obviously detiorated. I replaced the seals, ground in the valves which were not too bad and took the oportunity to drill out a sheared glow plug stem. Re-sssembly went well with a new head gasket etc. Apart from the blue oil smoke the engine ran pretty well prior my efforts. On re-start I was delighted there was no sign of the dreaded blue smoke. However I am now faced with much more smoke of the unburnt diesel variety. I decided to check the injectors and having read up on it cleaned them in caustic soda solution and thought i had made a big improvement. However on re-assembly the deisel smoke is just as bad. The engine appears to be firing on all four cylinders because if I loosen the injector nut on any cylinder the engine will become lumpy and change tone.

 

As the engine ran OK before my strip down, I feel I must have caused the problem. Any ideas or tests I could try please.

 

cheers

 

Paul Jackson

Redhill

Edited December 2, 2008 by jacksonp_uk

[RobinJ]

I recently did a top end overhaul on my BMC 1.5 diesel engine. This was primarily to overcome a serious oil burning problem which developed over a 7 day cruise in late summer. I identified this as most likely being the seals on the valve stems failing. On strip down these seals had obviously detiorated. I replaced the seals, ground in the valves which were not too bad and took the oportunity to drill out a sheared glow plug stem. Re-sssembly went well with a new head gasket etc. Apart from the blue oil smoke the engine ran pretty well prior my efforts. On re-start I was delighted there was no sign of the dreaded blue smoke. However I am now faced with much more smoke of the unburnt diesel variety. I decided to check the injectors and having read up on it cleaned them in caustic soda solution and thought i had made a big improvement. However on re-assembly the deisel smoke is just as bad. The engine appears to be fiing on all four cylinders because if I loosen the injector nut on any cylinder the engine will become lumpy and change tone.

 

As the engine ran OK before my strip down, I feel I must have caused the problem. Any ideas or tests I could try please.

I can only think of two reasons why the engine is still producing black smoke.

Frstly cleaning the injectors may not have cleared the nozzles properly, if the diesel is not being properly sprayed from the injector it will affect the combustion process and can lead to black smoke. It may be worth having them overhauled?

Secondly, lack of clean air or incresed back pressure will affect the combustion process and cause black smoke. In this case I assume you looked at the manifold while the head was off and cleaned any deposits, this could be soot from burning oil or deposits from the air intake via the breather. Is the engine compartment well ventilated? Have you any air filter that needs cleaning? What sort of exhaust is fitted?

[John Orentas]

Hi Paul.

 

I am a little surprised that you cured the oil burning problem quite so easily, I would have been more inclined to suspect worn bores, however it may well be that your injection timing should now be checked.. These engines are prone to wear in the drive mechanism for the injector pump..

 

For a start undo the three bolts which hold the pump in place and rotate it in the opposite to the it's running direction, you may well end up moving the adjustment to a considerable degree before you get the engine running smoothly.

[bottle]

Gentlemen:

 

Not knowing the intricacies of this but it appears that jacksonp has got rid of the black smoke but now has white smoke (unburnt fuel) problem.

 

The little I do know, is not worth knowing so will now shut up.

[Tony Brooks]

Gentlemen:

 

Not knowing the intricacies of this but it appears that jacksonp has got rid of the black smoke but now has white smoke (unburnt fuel) problem.

 

The little I do know, is not worth knowing so will now shut up.

 

 

If he did what John said then he has probably twisted the pump too far. Diesels make black smoke to set too far one way & white the other, but I am blowwed if I can remember which. From johns post I suspect retarded gives white smoke.

 

I also very much doubt that simply dunking the injectors in caustic soda would do much more than remove the cosmetic carbon. If the nozzles were removed I would question how well their seats & the auxiliary spray hole were cleaned and how well they were flushed. Then there is the question of setting up and testing - are they dribbling? - what's the break pressure?

[John Orentas]

Tony, you have lived long enough to know that what people call 'White Smoke' is in fact invariably unburned fuel.. "Opposite to the it's running direction" can usually be interpreted as 'Advancing'.. In cases like this everybody cries "Injectors" though in my experience it is not often the case.. Get everything else right, then think about injectors.

[jacksonp_uk]

Tony, you have lived long enough to know that what people call 'White Smoke' is in fact invariably unburned fuel.. "Opposite to the it's running direction" can usually be interpreted as 'Advancing'.. In cases like this everybody cries "Injectors" though in my experience it is not often the case.. Get everything else right, then think about injectors.

 

Hi folks

 

Thanks for your replies.

 

It is definitely white smoke. The fuel pump was not disturbed during the strip down process, nor were the injectors at first. To clean the injectors they were boiled in caustic solution for an hour. I checked that the small bypass holes were clear (two were definitely blocked before I started! All the injector parts were cleaned with carb cleaner and paper towel before careful re-assembly. The spring pressure noted on dissembly was half a full turn plus around 5 degrees more.

 

Just thought I ought to clarify what has been done.

 

cheers

 

Paul

[Speedwell]

Does the white "smoke" go off as the engine warms up ? If so possibly a heater is not working, perhaps damaged in the repair. If it does not go off and is not improved by adjusting the timing, you must have compression too low to fire the diesel properly so valve clearance or sticking valve, presumably exhaust as sticking inlet causes horrible spitting in the inlet manifold. The exhaust valves should not have rubber seals on them.

Arthur

[OptedOut]

The spring pressure noted on dissembly was half a full turn plus around 5 degrees more.

 

I think I would get the injector pressure and spray pattern checked.

[John Orentas]

Hi Paul.

 

I would always advise people not to attempt any kind of cleaning or adjustment of injectors even removing them has it's risks, I think it is likely that you will have to get them professionally reset or replaced now..

 

When you say "It is definitely white smoke" how did you arrive at that conclusion, if you are in a position to carry out a little test, put your hand carefully into the "smoke" for a few seconds, then sniff your hand.. Does it smell of smoke or fuel.

 

A general comment, when working with engines, only try/test one thing at a time, otherwise if you do three things and something changes you don't know what the hell has caused it.

[LEO]

Hi,

 

I had similar problems when I did a top end overhaul on a BMC 1.5, carefully re-assembled it and it started to produce lots of white smoke. It transpires it was a early engine and BMC fitted them with sharp washers under the valve springs. When compressing the valves during re-assembly these washers caught on the rubber seals that fit on the valve stems, perforating them and allowing oil to drop down the valves into the combustion chamber or hot exhaust.

 

AMC (Blackpool) helpfully advised on the problem and suggested leaving this washer out, (which they did on their re-builds) - head off, washers removed, re-assembly, problem sorted.

 

I found AMC very helpful, on all things BMC - they are the specialists - (no connection). I dealt with them on a mail order basis (parts usually received by return) and got all spares from them - including a water pump. The engine no helps them to identify what you need.

 

LEO

[ditchcrawler]

Hi Paul.

 

I would always advise people not to attempt any kind of cleaning or adjustment of injectors even removing them has it's risks, I think it is likely that you will have to get them professionally reset or replaced now..

 

When you say "It is definitely white smoke" how did you arrive at that conclusion, if you are in a position to carry out a little test, put your hand carefully into the "smoke" for a few seconds, then sniff your hand.. Does it smell of smoke or fuel.

 

A general comment, when working with engines, only try/test one thing at a time, otherwise if you do three things and something changes you don't know what the hell has caused it.

My engine produces white smoke, unburnt fuel, As John says you can smell it. It has been suggested to me that it could be due to the valves not seating 100% and allowing fuel to escape on the compression stroke, however it is not bad enough yet for me to pull the head off and risk causing other problems. Paul said he reseated the valves, maybe one is not quite as good as he thinks.

[OptedOut]

head off, washers removed, re-assembly, problem sorted.

 

On some engines you can get the valve springs off with the head on (at TDC), not sure if this applies to a BMC.

[riverbargeman]

Hi any engine experts out there

 

I recently did a top end overhaul on my BMC 1.5 diesel engine. This was primarily to overcome a serious oil burning problem which developed over a 7 day cruise in late summer. I identified this as most likely being the seals on the valve stems failing. On strip down these seals had obviously detiorated. I replaced the seals, ground in the valves which were not too bad and took the oportunity to drill out a sheared glow plug stem. Re-sssembly went well with a new head gasket etc. Apart from the blue oil smoke the engine ran pretty well prior my efforts. On re-start I was delighted there was no sign of the dreaded blue smoke. However I am now faced with much more smoke of the unburnt diesel variety. I decided to check the injectors and having read up on it cleaned them in caustic soda solution and thought i had made a big improvement. However on re-assembly the deisel smoke is just as bad. The engine appears to be firing on all four cylinders because if I loosen the injector nut on any cylinder the engine will become lumpy and change tone.

 

As the engine ran OK before my strip down, I feel I must have caused the problem. Any ideas or tests I could try please.

 

cheers

 

Paul Jackson

Redhill

 

Hi there

 

Did you remove and refit the injectors? - One would hope so if you were carrying out a decoke and drilling out the broken heater plug stem.

 

The injectors on these engines have two washers each, one larger copper one which seats on the shoulder half way up from the injector nozzle and a second one which is smaller very thin and sits down at the bottom of the nozzle to as a heat shield. This second smaller washer has a radial ridge which squashes flat on fitting. It is a once only fit. ie it must be replaced when the injector is removed and refitted whether or not the same injector is refitted. These washers are very difficult to see in the head and usually remain in place with a build up of carbon. If you use a bic biro case and insert it into the injector seat in the head (with the injector out) and press down with a little force but not enough to bend the biro case then you can usually get the washer to bite on the taper of the biro and it can be withdrawn.

 

If you just fit new ones on top of the old then it is usual for the bottom of the injector nozzle insert to be sheared off which is a head off again to remove the broken parts and refit a new insert.

 

IF this is what has happened then the injector nozzles are very likely to have overheated and may very well need to be replaced or less usually now reseated and reset. Your best next move would be to remover and replace the lower and upper washers ( A few pence from AMC) and see how it runs, if there is no improvement within 5 minutes of reaching running temperature then it is likely that all or some of the injectors have become damaged.

 

I hope this helps