Thread: How big are the holes in a diesel injector?

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

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

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.

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.

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.

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

Originally Posted by 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.

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.

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