Injectors and Glow Plugs for Dummies - PeachParts Mercedes-Benz Forum

mowoc · #1 07-13-2009, 12:08 PM

Allright, I did some searching and apparently the GP/Injector discussion is pretty popular. It is so popular that I am now pretty confused.

My SDL has 181k on the clock. The GP's were pulled around 150k and the PO was told they were fine (I have the paperwork that indicates that at least). I beileve them to be the original GP's.

These should have been changed by now, right?

Also, I have noticed that there is some smoke coming from the car now on acceleration (black, and not too thick). It did not do that before. I understand that may be the injectors? I can have them tested, right?

Is there a Glow Plug and/or Injectors for Dummies thread that I could reference to understand these items?

Sorry if these seemed to be covered, but I am not really literate when it comes to Diesel topics. If there is a better way to ask these questions I am open to any and all suggestions.

As always, thanks for your help.

Diesel911 · #2 07-13-2009, 09:43 PM

Quote:

Originally Posted by mowoc

Allright, I did some searching and apparently the GP/Injector discussion is pretty popular. It is so popular that I am now pretty confused.

My SDL has 181k on the clock. The GP's were pulled around 150k and the PO was told they were fine (I have the paperwork that indicates that at least). I beileve them to be the original GP's.

These should have been changed by now, right?

Also, I have noticed that there is some smoke coming from the car now on acceleration (black, and not too thick). It did not do that before. I understand that may be the injectors? I can have them tested, right?

Is there a Glow Plug and/or Injectors for Dummies thread that I could reference to understand these items?

Sorry if these seemed to be covered, but I am not really literate when it comes to Diesel topics. If there is a better way to ask these questions I am open to any and all suggestions.

As always, thanks for your help.

As long as the GPs are working they do not need to be changed. If you have a Volt/Ohm meter you could use one of our DIYs or go to the Diesel Giant website and test your Glow Plugs without removing them.
How long Glow Plugs last seems to depend on if Fuel I burning OK in the Combustion Chamber and Carbon build up in that area.

If the PO kept his Engine "tuned-up" and in top shape I would expect the Glow Plugs to last longer than in a neglected Engine.

Other Factors are where you live. If it is extremely cold during part of the year you would be using your Glow Plugs more than where I am in S CA.

Next would be that a lot of City driving tends to cause more Carbon Build up which seems to shorten the GP life.

Another factor could be the other part of you starting system. The Battery its Cables (including the Ground strap) and the Sarter. If they are all in optimal condition starting is fast.

If you do end up replacing some Glow Plugs Members report that only Beru and Bosch Glow Plugs Hold up well. Totally avoid Autolite GPs; I like others have had a bad experience with them.
Also when the Glow Plugs are removed ream/clean the Carbon out of the Glow Plug holes.

Yes, Injectors can be tested but they must be removed from the Engine to do so but you have to pay for that.
Some Members have had good results by doing a "Purge" in hopes of cleaning the Injectors.

Learning takes time.
It might be helpful to go the the Library and get a book on how Diesel Engines work. Understanding how the various parts work will help you when you read the various Threads; to differentiate between what is a members presonal choice and what is actually needed.

If your Car is running OK I would not be in a hurry to start pulling parts off until you know why you are doing it. Spend some time reading the DIY Links on the parts you are concerned with.

Cr from Texas · #3 07-13-2009, 09:51 PM

As a point of reference, my GP's are all original and have not been touched. The injectors have never been out of the engine but I'm considering sending them to bkast for new nozzles and testing. First, I'm replacing the rack dampner pin in the injection pump.

Hit Man X · #4 07-13-2009, 10:23 PM

Quote:

Originally Posted by Cr from Texas

he injectors have never been out of the engine but I'm considering sending them to bkast for new nozzles and testing.

You'll be impressed how much better the car runs with just those.

Diesel911 · #5 07-14-2009, 12:13 AM

Quote:

Originally Posted by Cr from Texas

As a point of reference, my GP's are all original and have not been touched. The injectors have never been out of the engine but I'm considering sending them to bkast for new nozzles and testing. First, I'm replacing the rack dampner pin in the injection pump.

Good idea.
You might hold off on the Rack Damper until the rebuilt Injectors are Installed.
If you have the origional Injectors in you car the PO must have really done a good job taking care of his Car!

mowoc · #6 07-14-2009, 12:45 AM

Thanks all for the responses.

Once I got a little better understanding I was able to peruse the DIY a bit and figure out some stuff.

I am going to try the old italian tune up on the injectors to see how that works. I did have a problem eariler where the ALDA got all sooted up and was not working correctly. I think that may have caused some build up as I ran it a bit like that before someone here pointed me in the right direction. From my reading that type of build up can cause the car to smoke a bit.

As for the GP's, I don't know. I found a reciept for a reputable indy that had both Injectors and GP's out for testing at 146k (I have 181k now). They indicated they were both fine for whatever that is worth.

I also have a block heater, so I really don't rely on the GP's in the winter. I have noticed hard starting sometimes but I don't know if that is all GP related or perhaps a zealous operator.

On the bright side they also did a compression test. It indicated 300 straight across. From my reading that is good. I would kind of expect that given these engines and the fact that this car was pretty well cared for.

I will continue to fuddle my way through this stuff as I really like it. It is sometimes difficult to tell the difference between opinion and fact on this board. There are some fun discussions that I don't really follow as I am no where near as technical although I do understand most of the basics.

Y'all sure do know these cars.

whunter · #7 07-14-2009, 02:02 AM

Quote:

Originally Posted by mowoc

Thanks all for the responses.

Once I got a little better understanding I was able to peruse the DIY a bit and figure out some stuff.

I am going to try the old Italian tune up on the injectors to see how that works. I did have a problem earlier where the ALDA got all sooted up and was not working correctly. I think that may have caused some build up as I ran it a bit like that before someone here pointed me in the right direction. From my reading that type of build up can cause the car to smoke a bit.

As for the GP's, I don't know. I found a receipt for a reputable Indy that had both Injectors and GP's out for testing at 146k (I have 181k now). They indicated they were both fine for whatever that is worth.

I also have a block heater, so I really don't rely on the GP's in the winter. I have noticed hard starting sometimes but I don't know if that is all GP related or perhaps a zealous operator.

On the bright side they also did a compression test. It indicated 300 straight across. From my reading that is good. I would kind of expect that given these engines and the fact that this car was pretty well cared for.

I will continue to fuddle my way through this stuff as I really like it. It is sometimes difficult to tell the difference between opinion and fact on this board. There are some fun discussions that I don't really follow as I am no where near as technical although I do understand most of the basics.

Y'all sure do know these cars.

Trusting an OHM test is a common diagnostic error on glow plugs.
The glow plug is a HIGH temperature heating element = the element can (and does) frequently read OK on an OHM test but is bad/shorted.
The critical factor is electrode resistance at full operating temperature, testing at low ambient is not valid.

Heating to a minimum temperature of 850°C is critical for diesel engine start-up.
Glow plugs run 1000° - 1300°C = up to "2372° Fahrenheit" optimal temperature range.
This is why many members choose to remove the glow plugs, put them in a vice, and manual glow them (often finding bad units that OHM good).

The older Mercedes Benz diesels (pre CDI) have a Pre-combustion Chamber that houses the glow plugs.
Carbon build up on glow plug electrodes acts as an insulating blanket, reducing durability life and making the glow plugs ineffective.
Every time the glow plugs on engines equipped with a pre-combustion chamber are replaced, it should be reamed out to remove any carbon build up.

http://www.wellmanautomotive.com/glowplugs.php

http://www.ngk-dpower.com/en/technik/keramik-gluehkerzen/

Excellent study material.

Glow plugs link thread All diesel models
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread.html#post1019018

Starter health is important to your diesel!!!
http://www.peachparts.com/shopforum/diesel-discussion/107318-starter-health-important-your-diesel.html#post739798

Cold weather starting links
http://www.peachparts.com/shopforum/diesel-discussion/137674-cold-weather-starting-links.html#post1018529

Other links that may interest you.

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Lower Micron Fuel Filter Mod

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Fuel Sender 85 300D- Cleaned (Pics)
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MB diesel filtration, how it works.
http://www.peachparts.com/shopforum/diesel-discussion/141211-mb-diesel-filtration-how-works.html#post1055075

fuel filter change
http://www.peachparts.com/shopforum/diesel-discussion/112664-fuel-filter-change-post824006.html

Diesel filters, no tank strainers please.
http://www.peachparts.com/shopforum/diesel-discussion/140349-diesel-filters-no-tank-strainers-please-post1046422.html?posted=1

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http://www.peachparts.com/shopforum/diesel-discussion/105304-biobor-what-why-do-i-need.html#post723857

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http://www.peachparts.com/shopforum/diesel-discussion/115952-filters-fungus-biocide-etc-post823378.html

Algae Clogged Filter Pic StarTron WORKS !
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Braided fuel lines weep. 1984 300TD turbo
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300SD Fuel Filter Replacement Instructions
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240D fuel tank removal and cleaning
Good for any W123 sedan.
http://www.peachparts.com/shopforum/diesel-discussion/92826-240d-fuel-tank-removal-cleaning-post813925.html

Check out this fuel pickup screen
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http://www.peachparts.com/shopforum/diesel-discussion/166888-recommended-diesel-fuel-additives.html#post1298228

fuel additives
http://www.peachparts.com/shopforum/diesel-discussion/32674-fuel-additives.html#post179712

Additives
http://www.peachparts.com/shopforum/diesel-discussion/89658-additives.html#post589420

Diesel Engine Additives (Fuel, Oil, Trans, Brake, etc.)
http://www.peachparts.com/shopforum/diesel-discussion/198602-diesel-engine-additives-fuel-oil-trans-brake-etc.html#post1607735

Why Put Transmission Fluid In Diesel Tank?
http://www.peachparts.com/shopforum/diesel-discussion/51956-why-put-transmission-fluid-diesel-tank.html#post304476

Alternative fuel links (Diesel)
Alternative fuel links (Diesel)

Have a great day.

Cr from Texas · #8 07-14-2009, 01:43 PM

Quote:

Originally Posted by Diesel911

Good idea.
You might hold off on the Rack Damper until the rebuilt Injectors are Installed.
If you have the origional Injectors in you car the PO must have really done a good job taking care of his Car!

I am the PO!

Diesel911 · #9 07-14-2009, 02:40 PM

Quote:

Originally Posted by Cr from Texas

I am the PO!

Sorry, mowoc began the thread. I posted and when you posted after that I thought it was mowoc.
Or, is it possible mowoc got the Car from you (86 300DL)?

mowoc · #10 07-14-2009, 05:28 PM

I think they are two different cars.

I got mine from a guy in colorado who got it from an estate in CA.

I bought it on the side of the road with no real knowledge of diesels or if this car would even make it 10,000 miles. I thought it would be an airport car as I had a job where I flew every week. 10,000 miles would have lasted two years.

It has made it 30,000 and aparently it will go for a good while longer.

Diesel911 · #11 07-14-2009, 09:54 PM

Quote:

Originally Posted by mowoc

I think they are two different cars.

I got mine from a guy in colorado who got it from an estate in CA.

I bought it on the side of the road with no real knowledge of diesels or if this car would even make it 10,000 miles. I thought it would be an airport car as I had a job where I flew every week. 10,000 miles would have lasted two years.

It has made it 30,000 and aparently it will go for a good while longer.

When I bought my mercedes it had about 190K on it. Mine ran rougher that I wanted at Idle.
Since I had a Chinese Pop/Nozzle Tester I bought back in 92 when I got the Volvo Diesel I pulled the Injectors (they appeared to be the origionals) I tested and rebuilt them myself.

On all of them the central drilled holes were plugged with Carbon. There was a lot of erosion of the exposed metal between the Pintel and the Injector Heat shield and 3 where what I call dribblers (indicting that the seating area was shot); all had poor spray patteren.
Rebuilding them with new Spray Nozzles did a lot towards smoothing out my idle.

Below is a pic of the Stock Injector Spray Nozzles with the holes drilled in the pintel. 1 down the center and 1 acrossed. On mine both were plugged with Carbon.

That area of then nozzle works at idle and low speed and fuel quanities.
Just above the cross drilled hole at #14 is the Pintel seating area. When that area wears unatomized fuel will leak out before it is supposed and not burn well; it also detracts from the atomization of the rest of the fuel when the Pintle opens.

While under hard exceleration most Diesels will put out a little black smoke; I think this is normal. But, it should clear up and not leave a big trail of smoke behind it.

dablk1 · #12 09-04-2009, 06:51 AM

What's required to rebuild the injector nozzles?

vstech · #13 09-04-2009, 08:32 AM

also, remember, if you have black smoke, you are mixing more fuel than the available air can burn... check your air filter.

Diesel911 · #14 09-04-2009, 11:05 AM

Quote:

Originally Posted by dablk1

What's required to rebuild the injector nozzles?

This is what was done were I used to work:

Customer brings in Injectors for rebuild; the Injectors are tested.
The reason for testing them is for troubleshooting purposes. You want to get the money for the rebuild but at the same time you want to build-up some "Good Faith" with the customer.
He may have pulled a good set of Injectors and his vehicle is actually haveing other problems.
As mentioned in a previous post Pluged Air Filters can caus smoking.

After testesting the Injectors (on a Diesel Nozzle/Pop Tester) are taken apart. However, the parts for each Injector are kept together. This makes it easier to adjust the Pop/Opening pressure when they are assembled and the 2 parts of Spray Nozzle part of the Injector cannot be mixed with other Spray Nozzles as they are mated together (you may be reusing the Spray Nozzles if they tested OK; it it is up to the customer). Of couse they are cleaned; chemically and sometimes with an ultrasonic cleaning tank.

After that the precision flat surfaces of the Injector are lapped on a Lapping Plate till they are flat againe and carefully clened off.

The Injectors are assembled (with new Spray Nozzles if that is what the customer wanted) and tested again. The Opening Pressures for each Injector are recorded.

If the Opening/Pop Pressures of the Injectors are not correct you need to change the shim/s inside of the Injector to put a different spring tension on the Spring. This sometimes requires taking the Injector apart several times till you get it right. (You measure the shims/s and compare it to the Opening Pressure and gestimate the next size shim you will need.)

When you are testing the Injectors you are looking for a good spray pattern, the Opening Pressure, leaks around the body of the Injector and you bring the pressure of the Injector to 200 psi below the opening pressure to see if the seating area leaks (you are allowed x number of drips per an amout of time).

When setting the opening pressures all of the Injector opening pressures must be within 5 bar when compared to each other. A private shope rebuilding the Injectors will try to get this as low as they can without spending too much time on them.

A good fast tech working with a complete set of Injectors can do the whole job in 10-15 minutes for each Injector.

I think there is a Do It Your Self thread somewhere on the above.