This writeup is intended to help in diagnosing, servicing, repairing, calibrating and replacing worn, old or damaged injectors on M21 motors used in vehicles such as the 524td, 324td, Vauxhall Vixen motorhome and the rare Lincoln Mark VII.
HOW DO I KNOW IF I SHOULD SERVICE MY INJECTORS?
Any of the following may be signs of worn injectors if your engine is in otherwise good mechanical shape:
- -Rough idle, idle lope
-Injector "knock" or "nailing", strange combustion noises. May sometimes sound like piston slap or rod knock.
-Excessive black or white smoke
-Loss of power
Many diesel mechanics and techs believe they should be serviced or replaced every 60,000-80,000 miles.
ABOUT THE INJECTORS:
The M21 engine is considered an IDI or Indirect Diesel Injection motor. What that means is the injectors fire into a precombustion chamber or precup in the cylinder head. As a result, IDI motors typically have higher compression ratios, lower injection pressures and lower power output than TDI or CDI motors.
When an injector is worn or becomes damaged, you must replace the injector nozzle. While it is not necessary, you should replace ALL nozzles at the same time. That way, they will all wear evenly over their service life. The nozzle considered a wear item and disposable whereas the injector body is reusable and must be reconditioned before installation of new nozzles and calibrated after reassembly.
Quoted from a Bosch technical document:
As a result, it as been said by many that ALL DN0SD nozzles are interchangable while others state that some nozzles have slightly different dimensions. The M21 uses DN0SD259 nozzles.These nozzles are known as Delay Pintle Nozzles, and are nearly always used with the Indirect Injection Engine, and have part numbers like, DN0S"D"299A.--The "D" in inverted commas, refers to Delay type nozzle.
"DN" "0" "S" D "299A"
"DN" referrs to Pintle type nozzle
"0" referrs to the spray angle, whether its defined as a number of degrees or not.
"S" refers to the size of nozzle body.
and "299A" refers to specific characteristics of that particular nozzle ( apart from this number its not possible to find the charaterictics of the nozzle from the makers)
Any letters before the "DN" refer to the maker, eg. B, C, K, R, V are all Lucas / Delphi maker codes, Bosch generally use just the basic number.
DN0SD INJECTOR NOZZLE GUIDE:
This is my interchange guide so far:
DN0SDXXX - [Displacement] / [# Cylinders] / [HP] - Engine model
Known good fitments for the M21 will be in BOLD. Interchangeable nozzles will be underlined.
DN0SD259 - 2.4-6-114 - BMW M21, Fiat, Lancia
DN0SD248 - 6.2-8-130 - Early GM 6.2L
DN0SD265 - 3.0-5-122 - Mercedes OM617
DN0SD318 - 2.5-6-141 - Volvo 940, BMW 525tds, Opel Omega 2.5, Volvo 2.5
DN0SD297 - 1.9-4-76 - Volkswagen "AAZ" 1.9L Turbo
[More to be added, fitments updated]
[To be added] Special sockets, injector line care, fuel return barbs, issues concerning #4 "sensor" injector.
CLEANING AND SURFACING THE INJECTOR BODY:
[To be added] Solvent soak, sanding interface surfaces
CALIBRATION, "POP TESTING":
[To be added] Testing Equipment, testing at home v. shop testing, Shims, Pressures, Calibration fluids or different fuel types including Low Sulfer, Ultra Low Sulfer, Bioiesel and WVO and pressures. Spray pattern.
[To be added] Heat shields? Torque specs
OTHER INFO, TIPS, TRICKS, REMEDIES AND FAKES:
Automatic Transmission Fluid Flush:
[To be added]
[To be added]
Use and effects of Waste Vegetable Oil:
[To be added] Coking glycerin, thinning agents and effects, adequate preheating
Do we have any Bosch gurus here that can tell me if nozzles from any other injectors will fit our injector bodies?
I just got myself a pop-tester to service few cars (VW-TDIs) and while searching for nozzles I noticed a few different options for nozzle sizes. But there aren't any options to increase nozzle sizes for our injectors. And then it hit me. the basic design of a Bosch IDI injector hasn't changed much at all over the years. 300D, 524td, 6.5L GM, etc.. all have pretty similar designs.
So, in my mind.. I am thinking this. If any other nozzles DO fit these bodies, then we could potentially create higher-fueling injectors for the M21.
I came up with a formula to compare relative measurements of power and displacement of other motors.. if we take that information and plug it into our engines characteristics, it should give us an idea of what sort of increase we could see.
[Engine displacement] / [# of cylinders] = X [displacement per cylinder] * 6 [# of cylinders on M21] = fueling for "virtual displacement"
Lets just say 300D nozzles fit for a moment.
3.0L / 5 = 0.6 * 6 = 3.6L
Again, lets say 6.5L GM nozzles fit...
6.5L / 8 = 0.8125 * 6 = 4.875L
HOWEVER...if we look at power outputs for these motors things start to make less sense.
I'm going to stick with the 300D and 6.5L motors on this one..
HP (or torque) / [# of cylinders] = X [HP/cylinder] * 6 = XX
300D - 80HP / 6 = 16 * 6 = 96HP - Smaller total volume over stock
6.5L GM - 180HP / 8 = 22.5 *6 = 135HP - Larger total volume over stock
I'm just thinking out-loud here.. if anyone else has better information regarding physical dimensions of M21 injector bodies or nozzle measurements or even flow statistics please share.
If it turns out that other nozzles are interchangeable, it could become a better option than trying to track down replacements from Germany and could be plentiful and inexpensive.