Rebuilding / Pressure Testing Injectors

I have a injector rebuilding kit I used to rebuild the injectors on my diesel Mercedes. It is supposed to be compatible with any injectors using the proper adapters. Of course, the Tdi injectors are press-fit in, so how does one check the injectors to make sure everything is within spec?

Thanks,

h.ubk

What's pressed on a TDI injector?

The problem with calibrating TDI injectors is that they have two stage opening which you can't see on a pressure gauge.

On other cars the endpoint of the injector is threaded onto the head. My understanding of the AHU/1Z is there is a fastener and the injector tip is press fit.

I didn't know about the two stage opening. That just makes it more interesting.

h.ubk

No pressing into the head. The injector fits into the head on top of a solid copper gasket and a clamp holds it down.

Ok, fine. But it still is not threaded.

I'll try the question another way. Has ANYONE here PERSONALLY rebuilt their injectors and used a machine to pressure test the injectors? If so, how did you do it? My machine does not have a clamp to hold the injector in place.

h.ubk

you need a pop tester. reputable diesel dealers or ebay will provide one , but do you reallly know how to use one and apply the neccesary shims?

h.ubk said:

Ok, fine. But it still is not threaded.

I'll try the question another way. Has ANYONE here PERSONALLY rebuilt their injectors and used a machine to pressure test the injectors? If so, how did you do it? My machine does not have a clamp to hold the injector in place.

h.ubk

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Not something commonly discussed here. Member DrivebyWire does this as a service, I think Franko6 as well, you could try to contact them with questions.

miningman said:

you need a pop tester. reputable diesel dealers or ebay will provide one , but do you reallly know how to use one and apply the neccesary shims?

Click to expand...

Yes, I have the pop tester and stated I already rebuilt the Bosch injectors on my Mercedes. It is a very straightforward procedure if you have the right equipment. Generally, the shims are to compensate for 50 - 100psi difference on an otherwise good injector in order to bring all of the injectors into parity with each other.

h.ubk

I'd suggest starting by seeing if you can track down a supplier for the shims required for ALH-style injectors.

If you can't buy a shim kit there's no reason to research any further, and once you find out what shims are going to cost you can decide if it's worth your while to attempt this yourself.

The obligatory "TDI injectors have multiple pop pressures and therefore can't be set up using a pop tester" comment here...

Best you're going to be able to do with a pop tester is set the pilot pressure. You won't be able to set the main injection pressure. Your Mercedes IDI injectors were single stage, totally do-able with a pop tester, unlike the TDI ones.

Sent from my LG-H873 using Tapatalk

h.ubk said:

Ok, fine. But it still is not threaded.

I'll try the question another way. Has ANYONE here PERSONALLY rebuilt their injectors and used a machine to pressure test the injectors? If so, how did you do it? My machine does not have a clamp to hold the injector in place.

h.ubk

Click to expand...

I'm not sure what you're trying to hold.. The Cummins injectors, just like the vw ones, fit straight into the head and are clamped down against a crush washer to seal. Cummins uses a nut to accomplish this while vw uses a bolt through a rocker arm. Both have threads on the "diesel input" for connecting the injector lines from either an injection pump or pop tester. My pop tester has no requirement to hold the injector other than threading the test line to it.

vanbcguy said:

The obligatory "TDI injectors have multiple pop pressures and therefore can't be set up using a pop tester" comment here...

Best you're going to be able to do with a pop tester is set the pilot pressure. You won't be able to set the main injection pressure. Your Mercedes IDI injectors were single stage, totally do-able with a pop tester, unlike the TDI ones.

Sent from my LG-H873 using Tapatalk

Click to expand...

^^ this

Sent from my mobile look-at device

This is one of the few jobs on these engines that needs to be farmed out to a professional with the right tools and knowledge.....if you want it done right.

.....and that's coming from a 60yr old diesel mechanic that hates to have anybody else touch his toys!

h.ubk said:

Ok, fine. But it still is not threaded.

I'll try the question another way. Has ANYONE here PERSONALLY rebuilt their injectors and used a machine to pressure test the injectors? If so, how did you do it? My machine does not have a clamp to hold the injector in place.

h.ubk

Click to expand...

I have not PERSONALLY rebuilt a TDI injector but I have PERSONALLY disassembled and reassembled one and have PERSONALLY seen that if you have the right fitting you could connect it to a tester.

At least to the testers I've seen which simply support the injector by the line.

You don't need any clamp to hold the injector, you can just tighten the injector to the high pressure fuel line and let it hang from there ofcourse pointing it towards the collecting cup for atomized diesel because you don't want diesel all over the place.

The injector insert is held by an nut with very fine threads to the injector housing. You will need to tighten the injector carefully into a vise and using a deep 15mm socket(if I recall the size correctly) and loosen the nut holding the insert. Between the nut and the insert will be a lot of carbon buildup and the insert will be probably stuck with the nut. After removing them you will see two locating pins on the injector housing and a nipple that connects the injector needle and the springs. Below the springs there will be the shims for adjusting the opening pressure and they are stuck by surface tension. You could remove them with compressed air but you risk putting them into a lower Earth orbit .
You should clean all the parts with an ultrasonic cleaner. After that you can reassemble everything and lubricating everything with clean diesel fuel ofcourse using the new inserts. You should first use the old shims for opening pressure setting. Do not tighten the nut very tight but only enough so you don't get any leaks to ease dissassembly for further shimming if adjusting will be neccecary. After that you can test the opening pressure with your injector tester. The injector should open at aprox. 200bar with a loud pop. You could be safe with a opening pressure +-10 bar that does not need adjusting. Common practice is that a 0.05mm shim will add 5 bar to the opening pressure. After confirming the opening pressure you can close off the pressure gauge an test the injector by a few hard strokes on the hand pump to see if it makes a really nice fog of diesel an it should intermittently pop as you press the handle.

h.ubk said:

Yes, I have the pop tester and stated I already rebuilt the Bosch injectors on my Mercedes. It is a very straightforward procedure if you have the right equipment. Generally, the shims are to compensate for 50 - 100psi difference on an otherwise good injector in order to bring all of the injectors into parity with each other.

h.ubk

Click to expand...

This is the 2 stage injector, not like Old Mercedes screw in injector.
If you look injectors it says 220/300 Bar.Means it works on 2 stage pressure 220 bars and 300 bars, and you need to set both of them, Old Pop up injector tester can not do job for those injectors.

More info you get get form Pete , here:
http://www.dbwllc.net/

He is the only one I would send injectors to rebuilt it because it does BEST JOB ever.

There's pictures of pistons with holes/cracks on them due to improper injector operation. Things work until they don't...

This is such a critical part of the engine that I have ZERO comprehension of why anyone would look to play brain surgeon on (especially when the cost is nowhere near what a brain surgeon would charge!).

Again, keep in mind that just because one can do something doesn't mean that they should.

My nozzles were first set up by DBW's company and the balance was amazing even after 60,000 miles. I had a pump go south and just to be safe I sent my nozzles back to DBW to be checked out, and there were some issues that had developed causing lack of proper high pressure fuel delivery. Had I of not had the relationship with DBW, my nozzles would still be bad and I would be unable to fix them and I would have likely thought my new pump was the culprit instead. Sending my nozzles back to him was the best $100.00 I have spent in a long time.

Okay, R*2 you are crazy, now what? LOL DFIS in Portland will install the nozzles you have purchased elsewhere for $36.00 each, so this is another option. I did not ask DFIS if they warranty for 5 years like Pete does, so you will have to ask them yourselves.

Does anyone have contact info for Pete/ DBW? I am trying to order a hot swap set of injectors and need some questions answered. I filled out the form on the website last Friday but I don't know that it really submitted -- no confirmation e-mail or anything.

I did talk with KermaTdi and they were very friendly on the phone, but I am questioning working with them after seeing some reviews.

h.ubk

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