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BMC complicated question


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I did change the copper washers and the fire sealing ring when I took them out, I didnt change the lower thinner copper washer as I couldnt get the top hats out without wrecking them.

I agree with tony, and having worked in the automotive trade for a long time I'm quite capable of fault finding (and screwing up I spose ), my aim here is to do what I can to avoid being swizzed by cash greedy diesel specialists, and only go to them when I need to, cause I'm sure that even if theres nowt wrong with mi injectors I'll still be stung for over a hundred quid anyway.

my reason to test the spray pattern is to see if I have been a hairy-bum and biffed the pintle and wrecked one of the injectors, not so much to see how worn they are.

I maintain a couple of mazda diesel lift trucks, and the injectors have been sent for testing on these a couple of times, and both times the report was that the spray pattern was incorrect, so unless I'm being lied to which is quite possible, the pattern does change with time.

Edited by dr pepper
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I was a bit scared of doing that, with the pressures involved, it is dangerous.

I saw a video earlier of a bolinger engine running on you tube, linked from this site, that took me to another site which had an inector in a washing up bottle as a safety guard, so I think I will try that and see what happens.

I'm assuming that I should get 2 spray patterns, one from the pintle and one from the auxilliary jet, and presumably cone shaped, has anyone else tried this?.

 

 

In theory the auxiliary will only produce a significant spray during cranking when the pressure rise and hence needle lift is lower than when running, so if your engine ran on three injectors you just might find the auxiliary spray almost stopped.

 

You really need an adaptor between the pop-tester and injector for execking the auxiliary spray, but you can get it to spray if you pump slowly.

 

In my experience the main spray is a hollow cone with very few streaks (actually there should be no streaks) and the auxiliary hole will produce a solid cone of spray - often looks more like a jet.

Edited by Tony Brooks
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Hi again guys, it appears that I'm still having trouble with my manky bmc.

I removed the pushrods today, they seem straight enough, I checked the rocker shaft, and it too seems ok, I removed the injectors and tried to test them, the ploom pattern seems ok, except I cannot tell if the auxilliary jet is working or not.

 

Still not running well, misfires every few seconds, only a couple of ideas left, one is the engine does not have a thermostat fitted, so I was wondering if there is some over cooling, and the other is I seem to be getting a rattle from the exhaust (its a dry exhaust), and I was thinking if there is an obstruction caused when taking the head off preventing the engine from running well.

 

heres a couple of naff photos of the injectors, you can see the auxilliary but its impossible to tell whether they are clear or not, I'll have another look with the works handheld microscope tomoz.

 

 

 

 

med_gallery_6566_1_14701.jpg

 

med_gallery_6566_1_18311.jpg

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only a couple of ideas left, one is the engine does not have a thermostat fitted, so I was wondering if there is some over cooling,

 

If it helps your deliberations, my BMC didn't have a stat until I fitted one after some 6 months of ownership - the only downside was it never got much above 55C, and took half an hour to get to that temp. Apart from that it ran fine.

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Hi again guys, it appears that I'm still having trouble with my manky bmc.

I removed the pushrods today, they seem straight enough, I checked the rocker shaft, and it too seems ok, I removed the injectors and tried to test them, the ploom pattern seems ok, except I cannot tell if the auxilliary jet is working or not.

 

Still not running well, misfires every few seconds, only a couple of ideas left, one is the engine does not have a thermostat fitted, so I was wondering if there is some over cooling, and the other is I seem to be getting a rattle from the exhaust (its a dry exhaust), and I was thinking if there is an obstruction caused when taking the head off preventing the engine from running well.

 

heres a couple of naff photos of the injectors, you can see the auxilliary but its impossible to tell whether they are clear or not, I'll have another look with the works handheld microscope tomoz.

 

 

 

 

med_gallery_6566_1_14701.jpg

 

med_gallery_6566_1_18311.jpg

 

 

From the look of those nozzles I doubt the auxiliary spray will be working as intended but as I said its use is to aid cold starting and once running it does little.

 

I doubt you could bend a pintle because they usually snap off and then you can see its missing. Run your finger tip over the pintle and you should be able to feel how much is sticking out of the nozzle and thus if there is still a pintle.

Edited by Tony Brooks
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yep, they all have pintles, and it sounds like i need to get them cleaned.

 

might try the ultrasound tank back at the shop, with some clean diesel.

 

i have a programmable strobe on loan which is cool, you can 'slow down' the engine to a crawl, very interesting to look at one of the injectors and varying the strobe, looks like a slo mo replay, cant see the auxilliary, probably because its not working.

Edited by dr pepper
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In theory the auxiliary will only produce a significant spray during cranking when the pressure rise and hence needle lift is lower than when running, so if your engine ran on three injectors you just might find the auxiliary spray almost stopped.

In my experience the main spray is a hollow cone with very few streaks (actually there should be no streaks) and the auxiliary hole will produce a solid cone of spray - often looks more like a jet.

It is some years ago last time I saw 1.5 injectors under test, I don't suppose 1.8 ones will be any different either!

They seemed to produce three aerosols evenly distributed around the centre over an angle of about 10 degress?

As I didn't see one, how would the auxilliary spray come out?

The BMC has a combustion chamber, so any spray at a greater angle would simply wet the sides of the chamber.

Could it be that one of the main sprays is simply larger?

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It is some years ago last time I saw 1.5 injectors under test, I don't suppose 1.8 ones will be any different either!

They seemed to produce three aerosols evenly distributed around the centre over an angle of about 10 degress?

As I didn't see one, how would the auxilliary spray come out?

The BMC has a combustion chamber, so any spray at a greater angle would simply wet the sides of the chamber.

Could it be that one of the main sprays is simply larger?

 

 

The spray from the pintle should be a hollow cone so the ones you looked at probably required attention or they were not 1.5 injectors, What you describe sound far more like the spray from a multi-hole nozzle but I have not come across a three hole nozzle before (but I have never actually worked in a pump room).

 

A pintle nozzles (like most modern engines use) has a flat end to the nozzle with the pintle stuck out or the centre. The pintaux nozzle (as in the BMC 1.x engines) has the pintle stuck out of a small "mound". There is an exceptionally tiny drilling through the side of the "mound" terminating on the seat of the injector needle valve.

 

With the injector in good order and the engine running normally the needle lifts far enough so the fuel all exits past the pintle. Whilst starting (cranking) the speed of pressure rise is slower so the needle partially lifts so forcing some of the fuel out of the auxiliary spray hole. (which is why I say this being blocked will not make a significant difference to the engine once it is running).

 

Both the main and auxiliary spray are directed into the small pre-combustion chamber which is probably about the size of a prune and at the time of injection is full of highly compressed, dense, fast rotating air. The pressure rise as the fuel starts to burn forces the air, gases and burning droplets of fuel back down a hole (say about 1/4 inch diameter) into the combustion chamber (cylinder) where the burn is completed.

 

However indirect injection engines can be a bit of a sod to start in the cold, hence the need for glowplugs. The auxiliary hole directs a small spray into the hottest part of the pre-combustion chamber which I assume is around the glowplug tip.

 

I still come back to "once its running do not worry about the auxiliary spray" and its far more likely to be a problem with the main spray pattern or even a needle sticking partially open (dribble). Ultrasound is used to clean injector nozzles as is a centrifuge but that tends to be just the nozzles with their needles removed. Looking at the carbon build up I feel a test on a proper rig would be very illuminating.

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Ok so rockers, and rods are ok then.

 

Valves sticking could be evidenced by running (slowly), with rocker box off, you would see a puff of gas from offending valve)

 

If as you say its an intermittent misfire, then its got to be down to fuel system, but where? airlock in fuel feed/return? pump marginal. fuel pump ok?, diaphragm ok?.

 

Others have said their piece regarding the injectors, only we need to find if its on cylinder only or intermittent across any of the four. I'd be inclined to:-

 

a) perform a leakdown pressure test on engine

b)subsitute pump for a borrowed spare

c) get one new injector, and try it in each cylinder in turn

 

Finally, check injector pipe unions carefully for any grit

 

After that am stumped

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However indirect injection engines can be a bit of a sod to start in the cold, hence the need for glowplugs. The auxiliary hole directs a small spray into the hottest part of the pre-combustion chamber which I assume is around the glowplug tip.

This is also my understanding of how the side jet is used. It is quite easy to remove the nozzle holder to facilitate cleaning. I did this with mine and nothing flies out when you undo the nut and there is nothing delicate inside

Arthur

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This is also my understanding of how the side jet is used. It is quite easy to remove the nozzle holder to facilitate cleaning. I did this with mine and nothing flies out when you undo the nut and there is nothing delicate inside

Arthur

 

 

Yes - Undo the BOTTOM sleeve nut. Use spanner until the spring tension is lost. Lift nozzle off, remove needle taking care not to touch the mating surfaces and clean in said ultrasonic bath.

 

As long as the top nuts are not touched the beak pressure should be about the same when its reassembled, however removing the gum and glaze from around the needle seat might make it dribble and doing the same for any on the mating surfaces may increase the back leakage. Without a tester i am not sure I would want to attempt this except in dire emergency (say he who has had a DPA pump apart with a hammer screwdriver and pair of gland nut pliers - and it did run afterwards, unlike before.)

 

Just observe extreme cleanliness

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You mention the problem occurred after replacement of the head gasket.

Did you have problems with water in the cylinders due to a leaking gasket?

I had an old Landrover diesel that used to misfire and pump out white smoke, this turned out to be a bent conrod caused by a small amount of water entering one of the cylinders. You could check this by checking the compressions and looking for one that is out of tolerance.

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You mention the problem occurred after replacement of the head gasket.

Did you have problems with water in the cylinders due to a leaking gasket?

I had an old Landrover diesel that used to misfire and pump out white smoke, this turned out to be a bent conrod caused by a small amount of water entering one of the cylinders. You could check this by checking the compressions and looking for one that is out of tolerance.

 

 

I have been involved with all kinds of IC engines over the years and appreciate the the trouble engine makers go to to atomise the charge entering the combustion chamber. This increases the speed of burn of the fuel for maximum performance.

Atomisation is all - especially with thick diesel oil. This is why they pressurised to many bar.

VW even introduced two pumps to their latest diesel engines, trebling the pressure to maximise atomisation.

Trying to burn a jet of neat fuel is not what you want.

Almost every one ignores their injectors. Idealy they need cleaning or replacing every 50k miles or 2000 hours.

If you take your injectors to a specialist and ask to see them tested - they might let you watch.

I will guarantee you will see jets of fuel going of in all directions. What you should see is a beautiful misty cloud of atomised fuel.

 

Alex

Edited by steelaway
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Thans guys, had a good response this time.

 

I need to aquire an injector then, or borrow one of one off the guys at the marina, I have a spare dpa pump.

the 1.5 and 1.8 injectors are diffo, I have the 1.8 and they are physically bigger, the glow plugs are diffo to.

Your explanation is professional Tony, heres a couple of pictures of the pintaux if anyone else is interested, which by the sound of it they are.

 

I'll be messing again this weekend, and I will get this manky bmc to run well.

P.S. I've been building a boat stove, its nearly done, I'll be posting details when finished.

 

med_gallery_6566_1_22967.jpg

 

med_gallery_6566_1_42892.jpg

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