The Truth About Injectors ? - PeachParts Mercedes-Benz Forum

dave240 · #1 12-09-2002, 01:43 PM

I am searching for the truth. that is.

1982 240d 186,000
I am under the impression I have pre-ignition going on.
(faint tinging on accelleration)

I speculate that maybe I have a leaky injector perhaps causing pre-ignition, hence the tinging noise. Is that possible?

I took the car to an MB shop (35 years experience) The shop owner said "diesel injectors NEVER EVER, EVER! wear out"
he drove the car and said it is fine.

I of course am not convinced. I know for sure that these injectors can be re-shimmed to adjust for worn springs etc. I would think that after 20 years of service and 186K there may be SOME wear.

I don't want to talk myself into spending money, (i.e. shortage of that this time of year)
however, hate to buy new injectors as I have heard folks on this forum say that even new ones sometimes need to be calibrated prior to installation.

Does anyone know any injector TRUTHS?

md21722 · #2 12-09-2002, 02:33 PM

I think the easiest point to agree to is that they CAN be calibrated.

I've talked to people about this, some say they don't wear out, others say they definitely do wear out. My mechanic drives my car and says mine are fine, don't waste my money (but the car does soot quite a bit, leading me to suspect injectors).

-brian

rwthomas1 · #3 12-09-2002, 03:06 PM

I have heard the same thing-Injectors never wear out. I think this is BS. I have replaced injectors in two other non-MB vehicles and the difference was very noticeable. Much less smoking, more power and better fuel economy. Both used Bosch injectors as I believe does MB. Now I suppose the MB type injectors could be a superior design but I doubt it. My general rule of thumb is injectors last about 150K. I know I will take heat on this and I know many people who have double and triple that mileage on one set of injectors but there is no way high-mileage injectors perform "like new" or close to it. They are fairly cheap and easy to change so why not? RT

gsxr · #4 12-09-2002, 03:40 PM

I'd find a new shop. The owner is flat wrong. Injectors are made of metal and subject to 2000psi operating pressures. They do not defy the laws of physics. They do wear out. Typical life can be 150-300kmi, maybe even longer, if filters are changed regularly and you use a good additive now and then (i.e., Diesel Purge, RedLine 85+, etc).

Your problem sounds like "nailing" to me. Before you replace them, try a can or two of Diesel Purge, and follow the directions exactly. This stuff is magic and if it hano effect, then you may need new/rebuilt injectors. They will be ~$50 each and your set of 4 must be matched on an injector "pop" tester so they are all set at the same pressure, within 1 bar if possible (definitely within 3 bar). Either buy them online and take the set to a diesel shop for matching, or buy the set through a diesel shop and request the set be matched. If you don't have them matched, your idle will be rougher (unless you get REALLY lucky and they all happen to be set to the same pressure.)

Warning: New injectors MAY take several hundred miles before they work "better" than the old ones! Sometimes carbon builds up in the prechamber from the old injectors' poor spray pattern, and it takes a while of operating with a "good" pattern to burn the carbon out. Alternatively you can remove the prechambers and clean them by hand.

Good luck,

md21722 · #5 12-09-2002, 03:56 PM

Dave,

What do you think the dealer does when installing new injectors? Do you think they test their injectors, or are they pretested better than the normal Bosch injectors from Rusty and others?

Brian

gsxr · #6 12-09-2002, 04:05 PM

Now that's a good question. I honestly don't know. I suspect they have a pop tester at each dealer and test them before installing. They may not bother adjusting (re-shimming) if they fall within the max spec (a ridiculous 5 bar variation, I think) unless the customer requests it. Might be the subject of an interesting conversation with the dealer shop foreman sometime.

BTW, Brian, my email is down right now, my domain hosting server blew up... not sure if they will be able to recover everything (oh, great).

#7 12-09-2002, 06:53 PM

Injectors most certainly CAN fail. I have one that is noticeably nailing - bad enough that when it starts misbehaving, my idle even gets rough. They're my next step.

dave240 · #8 12-09-2002, 08:43 PM

Thanks Guys,

Although I don't know exactly what you mean by "nailing".
I will try the Diesel Purge.

Also, you say I can remove the pre-ingition chamber? Is it difficult to get out and clean?

dave240 · #9 12-09-2002, 09:13 PM

Thanks Ken,

Well, just based on the in-put from a kind few folks, the injectors of 186K miles should probably at least be pulled out and eye-ball'd if nothing else. Perhaps dropped off at a (good) MB shop and have the "pop-off" pressure checked. eh

All I have is the Haines manual. I think 1200 psi is the min. I'll have to check.

kweimer · #10 12-09-2002, 10:10 PM

Removal of the prechamber is not hard, but you need a special tool to pull the prechamber out. Injectors do "wear out", or more correctly, the pintel tips burn resulting in a stream of diesel fuel going into the prechamber rather than a spray pattern. Spray pattern is, IMHO, the main thing to observe when using a nozzle tester. I have had good luck getting good used injectors at our local pull-a-part---just look at the pintel tips to make sure they are not burned---about $7 each for the complete nozzle and holder.
Ken

fredjj · #11 12-10-2002, 09:26 AM

I had nailing/pinging this summer in my 240D at 210K mi. All the fuel ines were dry, so no air was leaking in causing the pinging. So I thouht it was time to get the injectors tested. I pulled the injectors, found a local Bosch shop and had them tested. The shop said the spray pattern and the pressures were within spec. They cleaned the injectors as well. I re-installed them and all was well for about two weeks, then the nailing re-appeared. Then, I ordered new injectors and all is well. There was speculation on another list that one or more of the injector's pintle(?) may have had some slight galling (from 200K mi of use) which was causing it to hang from time to time and not fully shutting off the flow of fuel. So, they do wear and in my case testing the injectors didn't show the wear.

Aaron · #12 12-10-2002, 10:48 AM

To the question posed about if dealers test their injectors...

NO..

They order the rebuilt nozzles from MB and sell them to you "as-is". And believe it or not, most of the time, the rebuilds are total junk! So if you get a set of nozzles from MB, take them to a diesel or Bosch shop and have them checked before you put them in.

#13 12-10-2002, 12:45 PM

Quote:

Originally posted by TANK
I am LOL Diesel Power! Your car is over 40yrs old, I guess the earth will stop spinning one day too. Your car is a credit to mb engineering, That's for sure!

Thanx Tank, but the 59 is not the one I'm wrenching on right now. The 190Db needs a complete overhaul. I'm getting the 80 240D that I just acquired back up to snuff.

#14 12-10-2002, 04:23 PM

Maybe someone can help. I rebuilt my injectors last year. I disassembled each injector, keeping each injector with its respective parts (Very important if you ever want them to work again)

. All the nozzles were sonic cleaned and reassembled. I did have to replace one nozzle. I popped tested them, and they were within 2 PSI of each other from the highest to the lowest, and they all sprayed a good pattern, but some would drip. (I think this is what causes the smoke) I installed them and the car ran really smooth. 8000 K miles later. If the temperature drops,<28F, it runs on three than four and finally five cylinders after about 2 minutes. The glow plugs are all good. If I dont start it during the day, I might as well drive home with the starter engaged, because it takes that long to start, and I finally understand what nailing means. I am about to purchase new nozzles, but I can get the Bosch ROB 0434-250-110 New upgrade for $48.00, or buy brand new ROB 0434-250-072 for $10.00. They tell me that they made the engine louder, but that was subjective. I have been told the nailing is cause by a plugged injector. I think the injectors are old enough that they are burnt, and despite the nice cleaning and calibrating I did, they fouled because of age and small pitting that can't be seen. I can also buy cheaper nozzles, but they are not OEM. I would never chance that. Any suggestions?

PeterG

#15 12-10-2002, 04:31 PM

Fast lane has new injectors for $41.26 a piece. For that price, I'd say buy 'em new and drop 'em in.