How big are the holes in a diesel injector?

[blue_mini]

Hi everyone,
I'm having issues with my defender 200 tdi running atm.

I pulled my injectors out and they did seem quite built up with carbon on the nozzle end. The holes were there but were extremely small. probably .1mm or smaller. It did look like there was a build up around them but scraping it lightly with a screwdriver did nothing.

I soaked them in brake cleaner for a few minutes and it did look to make the holes bigger.
Should i be using acetone and get my hands on an ultrasonic cleaner or something?
Cheers,
Joe

[PhilipA]

I would think the holes would be very tiny as the holes in a 4 hole petrol injector are tiny and they only work on 40PSI Vs thousands of PSI in a common rail diesel, however of course the diesel has to open for a much shorter period than petrol.
AFAIK , the holes are cut by laser and it was only this tech that allowed such small holes and common rail etc.
I would think that the fluid pressure used by common rail would overcome any carbon build up, and you are only seeing a cosmetic change.
Regards Philip A

[redrovertdi]

PhillipA- 200tdi is direct injection and not common rail. I dismantled my 300tdi injectors one at a time and cleaned in an aldi ultrasonic cleaner in warm water with a small amount of detergent, a lot of crap came off. car seemed to run better after but then the injectors started leaking in the head[minor weep but i could smell it but nothing i did would stop it-tightening and new crush washers!] so i ended up fitting another set i had.
Richard

[manic]

holes barely noticeable, no problem.

I doubt its a great idea to soak in brake cleaner and scrape. Take them to a diesel shop and have them spray and pop tested - usually free for the test. Then you will know if they could do with ultrasonic or need rebuild/replaced.

[Tank]

Blue mini, I don't know why people that have no Idea of what a diesel injector is or does **** around with them, the "Holes" are minute and scraping, esp. with a screwdriver will **** them up.
Why do you think there a specialty shops that specialise in Injector cleaning/adjustment, even your local mechanic sends injectors away to specialists for servicing. If you stuff an injector up it could result in melted piston or a runaway engine, Regards Frank.

[blue_mini]

Simple misunderstanding really, when i say scrape i mean a slow motion with the sharp edge of the screwdriver to see if i can dislodge what looked like a heavy carbon build up. This turned out to be just a discolouration of the injector nozzle where diesel had constantly ignited next to it.

And i was asking the question to confirm whether or not the holes are to be the same size as a petrol injector, of which i do have experience with. I apologise if asking such a simple question irritates anyone on this forum. I completed several searches on this forum and the wider internet and did not find an answer to the question I had.

And i put the injectors back in and it runs very well now, turns out the issue is the fuel solenoid.

[PhilipA]

PhillipA- 200tdi is direct injection and not common rail.

OK I must be getting more sidxelci.
For direct injection , the injector depends on lots of things to work properly, spring tension for "break" pressure etc, leak down %, spray pattern..

I remember my Porsche 924 turbo always started one cylinder at a time until I replaced the injectors. Before you say WTF , Bosch D Jetronic petrol injectors were very much like diesel injectors.

So probably the best cure is a new set and I recall postings from some time ago saying they are now pretty cheap.
Regards Philip A

[Tank]

Simple misunderstanding really, when i say scrape i mean a slow motion with the sharp edge of the screwdriver to see if i can dislodge what looked like a heavy carbon build up. This turned out to be just a discolouration of the injector nozzle where diesel had constantly ignited next to it.

And i was asking the question to confirm whether or not the holes are to be the same size as a petrol injector, of which i do have experience with. I apologise if asking such a simple question irritates anyone on this forum. I completed several searches on this forum and the wider internet and did not find an answer to the question I had.

And i put the injectors back in and it runs very well now, turns out the issue is the fuel solenoid.
Any scraping with a steel screwdriver will do damage to the nozzle holes, if any scraping is to be done use a soft scraper like a paddle pop stick or a soft brass wire brush. The size and shape of the nozzle holes is Critical to correct spray pattern, by running a hard object over the opening you can irreversibly damage them and by your admission of having done so shows that you have no knowledge of injector maintenance/repair. I have been a Mechanic for 50 years now and I dont fiddle with injectors, it is a specialist item, same as I send Auto trannies to specialists, I don't have the tools or expertise to service either.
You didn't "irritate" me, my point is if you don't know what the procedure is for cleaning an injector, take it to an expert before it costs you heaps and to warn others not to fiddle with things they have no specialist knowledge of, Regards Frank.

[Blknight.aus]

in a tdi injector I would expect the nozzles indivdual hole size to be in the vicinity of .08mm with a total area of somthing like .025mm^2

[LowRanger]

OK I must be getting more sidxelci.
For direct injection , the injector depends on lots of things to work properly, spring tension for "break" pressure etc, leak down %, spray pattern..

I remember my Porsche 924 turbo always started one cylinder at a time until I replaced the injectors. Before you say WTF , Bosch D Jetronic petrol injectors were very much like diesel injectors.

So probably the best cure is a new set and I recall postings from some time ago saying they are now pretty cheap.
Regards Philip A

I hope it didn't,because 924 turbos came fitted with K Jetronic injection,which have mechanical injectors,that work on a similar principal to a diesel injector.
D Jetronic injectors are purely electronic.

[zedcars]

For info the nozzle holes are anything from about 0.002" up depending upon spec and application (Inches that is-- Sorry I am old fashioned Brit)

The object is to inject high pressure fuel into a refined atomized state into the combustion chamber (if direct injection) so that it mixes evenly within the swirl of incoming air and burns evenly. This contributes to the delay or lack of it within the combustion period of the three phases of injection taking place. The discharge pressure is carefully calculated to mix under the high combustion pressures present the cylinder without causing dense pocketing of fuel within the air charge or eroding the piston combustion chamber edges.
The delay period gives the diesel engine its distinctive knock.

Indirect diesel engines generally have a pre-chamber (like older MB 614 units) the injection is less atomized since a different form of combustion takes place. In fact the nozzle tip has a different needle and seat form.

As previous mentioned by previous contributors it is essential that the needle lifts and snaps back on its seat with an abrupt cut off of fuel.
If needle and nozzles seats are eroded or the seat is poor, internal spring is weak, internal injector pipe /component exfoliation build up in the sac, fuel will dribble after snap closing causing soot build up on the nozzle exterior and a smoky exhaust.
Obviously it is essential that a line pressure is maintained in the injector pipe of older diesel engines so that stored fuel in the pipe is ready to inject without any delay by loss of pressure by dribbling.
On many diesel injector pumps of the older style the delivery valve has a sharp edge on it seat shoulder to add to the instant cut off fuel.
Measured by pressure drop on an oscilloscope it looks very much like the raster wave on a petrol engine contact breaker ignition system.
Typical pressures are about 1.5 Atm for this type of engine.

Now out of fashion to comply with modern E standards and CI power systems are mostly common rail these days. However the smoke emission from the older engines was largely counted large particles of carbon soot which was less harmful to humans and not embedding themselves deeply into lung tissue.

On the other hand the common rail system has only short injector pipes say like a Sprinter or none at all in some applications. Pressures are generally speaking much higher and so are the injector nozzles which can have multi stage injector opening to reduce the noise from delay. The snap closing is conducted by electronic/hydraulic control action. Typically the engine rail pressure is anything between 300 atm at idle to 1500 atm full power again depending upon spec /application. Hence internal erosion and exfoliation can be a problem with these injection systems.

Although some manufacturers are dismissive about these types of engines having a direct effect upon human health; medical reports suggest nano particle exhaust deposits are being deeply embedded into lung tissue especially of the young and old. These are on the increase especially in city and urban environments and my daughter has also noted a distinct increase in tissue contamination of cadavers lungs dissected of late. Certainly cause for concern if you work on modern diesel engines like me.
Food for thought
Dennis
zedcars

[PhilipA]

I hope it didn't,because 924 turbos came fitted with K
Jetronic injection,which have mechanical injectors,that work on a similar
principal to a diesel injector.
D Jetronic injectors are purely electronic.


Of course. I should have referred to my Bosch book, but all i did was think " they weren't L jet, what was before that?" What is a D and K between friends.
Regards Philip A

[isuzurover]

...What is a D and K between friends.
Regards Philip A

As long as you are both consenting adults I suppose it is OK??? :eek:

[Blknight.aus]

not to dispute Zedcars on his theory work (its pretty much spot on) his pressures are low by about x10.