Injector Refurb

[DubDick]

Just got a few question around TDi (direct injection) injectors.

Can you remove them and do a refurb yourself?

I'm sure I can get access to an ultrasonic tank to clean them but testing them could be a little trickier.

Also should diesel injectors actually atomise the fuel or just shot it straight and narrow?

Cheers.

[STEWY L]

where are you living?

[DubDick]

Hampshire

[Crasher]

I get my local Diesel specialist to overhaul VEP TDI injectors but PD units I buy from Bosch exchange. It isn’t a DIY proposition as you can’t test them after rebuild without a specialist test rig.

[DubDick]

Okay, how about my other question.

Do the injectors actually atomise or is it a straight jet?

Mines a T4 TDi with direct injection. As far as I'm aware that isn't even VEP, or is it?

Thing is, I was talking to a guy last weekend who is a diesel specialist (appearntly?), hold told me that they test injectors by pumping them up to see if they atomise correctly. Not mention of checking break pressure for both stages or even measuring the volume delivered.

I thought that only petrol injectors atomise, diesels shoot straight - if so then this guy was nothing but a bulls### merchant.

This is all leading to me deciding what to do about my smokey van.

It's a 88hp with the stanadyne injectors and if it's going to cost much to get them looked at then I'll just gret some Bosch injectors (as used on the 102hp).

Can you get upgraded nozzles for stanadyne injectors?

[Crasher]

They have four jets and are water drilled; even polishing them with Scotch Brite will block the holes. VEP means Verteiler EinspritzPumpe which means distributor fuel injection pump (http://www.dict.cc/english-german/distributor+fuel+injection+pump.html) so yes yours is VEP. Uprated nozzles on their own will just make it smoke, find a Bosch diesel centre and take them in for overhaul. I am just rebuilding a 2003 AJT which twated 5 valves when the water pump failed, the injectors look poor and so I may suggest he has them rebuilt.

[carbon]

All diesel injectors atomise the fuel.

The only thing that ignites the fuel in a diesel engine is the heat generated by compressing the air within the cylinder, the glow plugs are only there to aid cold starts. Finely atomised diesel ignites easier than one large droplet due to the larger overall surface area of the atomised fuel.
The machine used by your diesel specialist is a pump but is does have a pressure gauge to check the operating pressure of your injectors.
The injector doesn’t measure the volume of fuel delivered the injection pump controls this.
If the nozzle on an injector is worn then the pressure that it works at can be lower than it should be, this can lead to the fuel not being atomised correctly which may be the cause of your smokey van. Without having your injectors tested it’s difficult to tell.

[DubDick]

The only thing that ignites the fuel in a diesel engine is the heat generated by compressing the air within the cylinder

I thought that as well a little while back - Boyles Law.
Then I had a think about it and a chat with a mate who's a Physist and it turns out that no heat is generated during compression of gas. In fact it cools slightly. It's a chemical reaction to do with partial pressure of gas I think that causes diesel to spontainiously combust under pressure.

I think the glow plugs are a way to help the cylinder to achieve pressure, or to make the diesel combust easier but it isn't the temperature that makes it happen.
Just though I'd say...:approve:




The injector doesn’t measure the volume of fuel delivered the injection pump controls this.


Yes, I agree but if you measure the amount dispensed over a period of time at a fixed pressure you can make sure the injector isn't blocked or the nozzles haven't worn too much. Oversized nozzles will allow more fuel to pass. This would be a good way to assess the wear of an injector.




If the nozzle on an injector is worn then the pressure that it works at can be lower than it should be, this can lead to the fuel not being atomised correctly which may be the cause of your smokey van. Without having your injectors tested it’s difficult to tell.

Mine is the AJT, similar to the ACV but with smaller injectors. This makes the injector pressure higher. If I was to fit the Bosch injectors as used on the ACV they would work without changing the fuel map, the pressure would drop but the engine would not become smokey. As far as many people have found there are very few difference between the AJT & ACV.
ACV has an intercooler, larger Bosch injectors and a slightly higher compression ratio.
I also have an intercooler on mine and run a tuning box without smoke.
The smoke is during warm up so that is why I suspect my injector are passed their best and probably have a bad spray pattern or something.
The engine has done 90k so I'm guessing the injectors may be tired. A guy as Bosch said that an injector should be good for around 100k, after then it's new nozzle time.

The question is should I get my stanadyne injectors checked and maybe refurbed or go for a set of new injectors to give the engine a boost.
I'm happy to stay with my stanadyne injector bodies if you can get slighlty over sized nozzles, can you get these?

The guys on the T4Forum use Bosch injectors as you can only get the very oversized .216 nozzles for that type but if a 1 step upgrade was avialable for stanadyne then I'd be happy with that.