1987 300 TD - Rebuilt one of my injectors today... - PeachParts Mercedes-Benz Forum

1987-300TD · #1 08-23-2015, 01:19 AM

I have no idea how many miles are on my injectors. Odometer has not worked for 1+ years and it is not even the original. (It is not even the proper part number.)

So today I decided to start rebuilding my injectors. I cleaned the heck out of the one I did. Used a nylon brush to clean the inside. The insides were stuck together with grease.

Cleaned out the area where the injector screws to the headers. Took extra precautions not to drop anything into the chamber.

Tighten everything down to 55 ft lbs. Reconnect the hard line. Reconnect the return lines.

Now injector #6 knocks like I have marbles in there! Let it run for approximately 1 minute. No change.

I did realize afterward that I did not replace a shim in the injector. Could this be the problem?

Any thoughts? I was hoping to replace them without pop testing. One of the how-to's I read recommended replacing the injectors one at a time as it helps to keep air out of the system.

Should I pull them all and get them all balanced? Advice?

Thank You!

bsmuwk · #2 08-23-2015, 01:32 AM

proper preparation prevents poor performance

In order to do this properly, you absolutely should have a pop tester. You can get close without, but you should have one.

Not installing the shim under the spring will 100% cause your nailing. That fuel is being injected FAR too early. On a turbo car, that injector is designed to open at 135-140 with new nozzles, or 115-120 bar on used nozzles, removing the shim is causing that injector to open at 80-100 bar, which is FAR too early! !

You haven't done any rebuilding if you hadn't replaced the nozzles, if you did, well, you need to get them balanced. If you hadn't replaced the nozzles, external cleaning doesn't do anything for the nozzles, which is what screws up injectors in the first place. Pintle seats in the nozzle erode and causes poor pop/spray. There are special brass scrapers that correctly "re lap" the seat of the needle for correct spray/pop. You also need to re lap the other contact surfaces in the injector as that's how the injector seals itself, it's all internal. There is no saving a bad nozzle though, so if the injector is still popping/spraying poorly after service, it needs to be replaced. I don't remember if you need SD 265 or SD 310 nozzles.

Take that injector out, reinstall the shim and do yourself the favor and send them to someone who can properly service the injectors! You'll be happy you did!

Diesel911 · #3 08-23-2015, 01:35 AM

Unfotunately people use the term rebuilt or rebuild rather loosely.

In order to do the complete job you need a Diesel Nozzle Tester/Pop Tester.

Vince Walden how to rebuild IDI Injectors.
vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors

ah-kay · #4 08-23-2015, 02:28 AM

The OP 'did not replace' the shim. I don't think he wrote 'did not install' the shim. It does not matter you replaced the shim or not. Shim does not wear out to the extend that it will affect the pop pressure a great deal.

Prior to buying a pop tester I have done injector without pop testing them and the car ran just fine. I scribed the 2 half before I disassembled it and torque it back to the mark, or very close to it. This is to ensure everything was back to what it was. Not sure whether you did that but I would definitely pop test them now.

bsmuwk · #5 08-23-2015, 03:10 AM

Quote:

Originally Posted by ah-kay

The OP 'did not replace' the shim. I don't think he wrote 'did not install' the shim. It does not matter you replaced the shim or not. Shim does not wear out to the extend that it will affect the pop pressure a great deal.

Prior to buying a pop tester I have done injector without pop testing them and the car ran just fine. I scribed the 2 half before I disassembled it and torque it back to the mark, or very close to it. This is to ensure everything was back to what it was. Not sure whether you did that but I would definitely pop test them now.

Sure,

but he wouldn't know what to replace the shim with without a pop tester anyway, so now the whole thread is a moot point until further info. lol

m1tch · #6 08-23-2015, 06:15 AM

Am I correct that there are different sized shims for rebuilding the injectors? I might look at rebuilding mine at some point - I will be getting/building a pop tester, just need to check what else I would need to do the job (apart from the new nozzles etc).

funola · #7 08-23-2015, 07:21 AM

Quote:

Originally Posted by ah-kay

The OP 'did not replace' the shim. I don't think he wrote 'did not install' the shim. It does not matter you replaced the shim or not. Shim does not wear out to the extend that it will affect the pop pressure a great deal.

Prior to buying a pop tester I have done injector without pop testing them and the car ran just fine. I scribed the 2 half before I disassembled it and torque it back to the mark, or very close to it. This is to ensure everything was back to what it was. Not sure whether you did that but I would definitely pop test them now.

I read and interpreted the OP's post same as bsmuwk. The OP did not mention 'replacing the nozzle'. Going by your interpretation of the OP's post, the OP must think rebuilding an injector requires only replacing the shim?

m1tch · #8 08-23-2015, 08:21 AM

I am guessing the OP also replaced the injector sealing washers as well.

bsmuwk · #9 08-23-2015, 06:46 PM

Quote:

Originally Posted by m1tch

Am I correct that there are different sized shims for rebuilding the injectors? I might look at rebuilding mine at some point - I will be getting/building a pop tester, just need to check what else I would need to do the job (apart from the new nozzles etc).

Yes, different thickness shims decrease/increase the pop pressure in small increments. It's best to get a large assortment of them to bring your injectors into balance. You can be off +/- 5 bar and everything will be fine, beyond that, you'll start getting small vibrations in how the engine runs as incorrect pop pressure effectively changes the injection timing advance or retarded depending on the pop.

When you get your tester together, before disassembling the injectors, pop them all and pick out which ones are closest to the factory pop (115bar NA/ 135bar T), do those injectors first without replacing the shims, chances are they'll be perfect. The rest will need adjusting.

2 out of every 6 injectors I do end up not needing any balancing after nozzle replacement. With age the springs lose their springiness and need additional shim to bring back into spec. Replace the injector heat shields when doing the job, your fresh nozzles will thank you. I don't bother replacing heat shields if I'm simply cleaning the injector, the nozzle face has already sort of molded itself to it's spot. I don't recommend not replacing the shields, but I haven't had a single one leak on me, so do with that what you will. New nozzles get new shields, always.

1987-300TD · #10 08-24-2015, 09:11 PM

Thank You All for your responses. Yesterday and today were very busy as the kids went back to school.

To clarify, I rebuilt 1 of my injectors over the weekend. I installed a new Monark tip. The old one had a bunch of grease caked between the exterior of the tip and the interior of the injector.

I was unsure what to do with the shim as other injectors I had did not have the shim when dismantled.

I replaced the shim and the injector is in my car. The knock is still there but Much Less pronounced. I am planning to rebuild the other 5 with new tips. I am then going to pull them all and get them balanced. There is a J&S Diesel here in Vegas.

I now have a puff of grey smoke when accelerating. Could this be caused by the injectors not being balanced?

Again, Thank You All!!!

Diesel911 · #11 08-24-2015, 09:21 PM

Quote:

Originally Posted by 1987-300TD

Thank You All for your responses. Yesterday and today were very busy as the kids went back to school.

To clarify, I rebuilt 1 of my injectors over the weekend. I installed a new Monark tip. The old one had a bunch of grease caked between the exterior of the tip and the interior of the injector.

I was unsure what to do with the shim as other injectors I had did not have the shim when dismantled.

I replaced the shim and the injector is in my car. The knock is still there but Much Less pronounced. I am planning to rebuild the other 5 with new tips. I am then going to pull them all and get them balanced. There is a J&S Diesel here in Vegas.

I now have a puff of grey smoke when accelerating. Could this be caused by the injectors not being balanced?

Again, Thank You All!!!

It is hard to say.

Just swapping in a New Injector Nozzle does not equal a rebuild. Also swapping the Injector Nozzle can also change the opening pressure; that could be a good or bad thing.

Somewhere between 100K and 150K the Injector Nozzles are worn out. And, before that they should have been checked to see if the opening pressures were OK and they were balanced.

Inside of the prechamber the Injector sprays down onto the Ball Pin. I believe that the Ball Pin sort of mask problems with the Injector Nozzles; especially after the Ball Pin is hot.

m1tch · #12 08-25-2015, 03:11 AM

You will need a pop tester, if the pressure is out of spec then the injector can fire too late or too early (eg its waiting slightly longer for the pressure in the line to build before injecting).

When changing the other injectors I would also check the condition of the ball inside the prechamber just to make sure its in good condition and not come loose.

1987-300TD · #13 08-26-2015, 12:11 AM

M1tch, how does one inspect the ball in the prechamber? Does anyone have pics?

Also, what is the MB part number for the injectors? I would like to purchase an extra set so I do not lose my DD.

TIA!

m1tch · #14 08-26-2015, 02:42 AM

Quote:

Originally Posted by 1987-300TD

M1tch, how does one inspect the ball in the prechamber? Does anyone have pics?

Also, what is the MB part number for the injectors? I would like to purchase an extra set so I do not lose my DD.

TIA!

Check out this video showing the different designs, you should just be able to shine a light into the prechamber area whilst the injector is out:

https://www.youtube.com/watch?v=8uTuk1RZRjk

Also here is a video on the injector rebuild showing any issues plus the use of a pop tester.

https://www.youtube.com/watch?v=kT8HjETFDx4

marko606 · #15 08-26-2015, 03:09 AM

Yes, you should have an injector pop tester. Yes, you should clean the heck out of the injectors. And yes, you should clean and sand mating surfaces of the injectors. But, most importantly, you should also have a set of shims in various sizes. A rebuild should not be attempted if you do not have shims. And these little things are not easy to come by. Or cheap once found. If anyone has some extra shims laying around send them my way.