This is on the '82. I am getting harder starts with a few missed (or even a stall) on one cylinder if I don't glow for 10 seconds and nailing on a single cylinder (I think) that has gotten worse over the last couple weeks or so. Car drives fine and it sounds fine over 1000rpm.

Here's what I have done:

- injectors are new Bosch NOS rebuilds 6k miles ago and have been running great
- checked glow plugs, all .8 ohms. strip fuse OK.
- checked valve clearances, all were fine, 2 were slightly tight and adjusted
- checked chain stretch, 4 deg by lining up cam marks. consistent with what it has been, no major change there
- loosened injector lines, and noted when cylinder #4 shut off, nailing went away
-swapped #4 injector with #5 injector. it really sounded like the nailing followed the injector after repeated comparison.

So naturally I took the injector to the local Bosch diesel shop to have it popped and sprayed. And it tested perfectly, I saw the test myself. Popped at 135 bar and the spray looked good. Huh

I was really sure it was following the injector. Positive in fact...but I saw the test myself.

What should I try next? Have I overlooked something? Is there any way an injector can test good and still ping/nail?

Thanks for reading along...
dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Sorry, but I don't have any ideas on what might be your problem but I'm hoping to get some info from you as I seem to be experiencing similar problems. Does this happen ALWAYS or only on a cold engine? Does throttle input help and, and once it warms up how does it idle?

Thanks.

have you tried leaving it on a block warmer to see if that helps?

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'81 300D - swapped to a 617.951 turbo motor with a 150 amp alt.

Lately, the knocking has been happening all the time, even after reaching full temp. The stumbling/miss is only when 'cold'. I say cold in quotes because this is all happening in July and August when it never gets below 60 degrees in the garage where the car is.

the starts are better when warm, but even with the engine lukewarm, it likes to have a long glow cycle to get running smoothly instantly.

->have you tried leaving it on a block warmer to see if that helps? <-

no, haven't tried that. easy enough to try tonight.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I myself are trying to find out just how exactly these MB diesels are supposed to sound at idle. Mine to accelerates fine, but at idle there seems to be a bit more 'clank' especially when cold. Is this normal?

If I exchanged #4 with #5 I do not think the difference as to where the abnormal sound comes from would be as obvious enough for me to tell for sure where it was coming from.

The problem could be that the drilled central hole in the injector pintel is clogged. This hole is supposed to give some pre-injection at idle speeds. So you will actually have 2 spray patterns to look for. One through the central hole where the person working the handle of the pop tester has to take short strokes (to simulate an at idle fuel quanity) to get the fuel to come out of that central hole- and then long deep strokes to simulate a larger than idle quanity of fuel (it is in the Factory Manual CD).
In short the central hole can be plugged and the main spray pattern can look good.
Please sea post #44 for a picture of the central pintel holes:
http://www.peachparts.com/shopforum/showthread.php?t=181392&highlight=central&page=3

While the both injectors are out it is a good idea to get a strong light and look inside the Pre-Combustion Chambers and see if the Ball Pin is still in good condition.

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84 300D, 82 Volvo 244Gl Diesel

At 213K, the prechamber might be the problem. Either a loose or missing ball or some plugged holes at the tip.

The SD had plugged holes in the prechamber and loose shafts at 185K. It's definitely likely on yours.

After concluding that the nailing travelled with the injector I had the motor in perfect condition for a compression test, so I went ahead with it...

#1: 380 psi
#2: 360 psi
#3: 370 psi
#4: 220 psi (260 psi after squirt of oil)
#5: 250 psi (260 psi after squirt of oil)

I was swapping the injector between 4 and 5. I could clearly hear the nailing both in the air and with the stethoscope. So I tried the 'faulty' injector in #3 - the nailing went away. Nailing is now pretty much gone, and I could no longer hear any nailing in the stethoscope. Ill see how the starting is tomorrow morning.

I am so confused...it seems that injector doesn't like low compression cylinders?

So it looks like I am a good candidate for a head rebuild from metric? (Brian - Ill definitely go for new pre-chambers at that time)

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Do you have the atomizer ball in the PC still on 4 and 5?

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

ALso known as the Atomizer Ball.

Low pressure on 2 adjacent cylinders is sometimes linked to a head gasket leak between cylinders. Fill one cylinder with pressurized air as if you were doing a Cylinder Leak Back Test and listen to the other cylinder with the injector out.

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84 300D, 82 Volvo 244Gl Diesel

Without the atomizer ball he is going to get nailing on those cylinders. Low compression would not affect the injector timing in any manner.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

winmutt - I looked for PC balls 6k ago when I had GP's out and they were there just fine.

As I mentioned the nailing had been following the injector - until I took that injector off the low compression cylinders and now everything seems to be alright. Still a little noisy/clangy but not a hard knock like before. I cannot hear obvious nailing with the stethoscope like before.

Diesel911 - I will do a leak down - thanks for the tip. I need to get an air compressor and a leak down tester.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

The reason I mention the balls is that with those gone you will have premature injection as they delay the overall timing. This would lead to nailing. I suppose it is possible that poor compression might affect the nailing... It would certainly lead to hard starts etc.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

More crazy ideas.
I would think that the Atomizer Balls/Ball pins would not help much until they are hot so they do not do much when you first start the car and the engine is cold.
I would also think that low compression would cause late and ignition as the temp of the compressed air in the cylinder would be lower.
(an interesting experiment for someone- at what degree on the Crankshaft is the compression pressure at the maximum.)
Also I believe the decreased density of the compressed air in the lower compression Cylinders allows the fuel injected to penetrate further into the combustion chamber before it ignites.
You end up with deeper fuel penetration and late ignition with the fuel burning some place down further in the combustion chamber than it is supposed to.

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84 300D, 82 Volvo 244Gl Diesel

Concerning the Ball Pins; lot of things can happen to an engine in 6k.

You will need a fitting to connect to the air compressor hose and that will connect to either a Glow Plug adapter or an Injector adapter. Compression Tester kits have both Glow Plug and Injectors but I do not think the fitting that screws in is compatible with an air hose coupling.

Any sort of safe pressurized gas could be used (Oxygen would not be safe) and if a high pressure gas would need a regulator to bring it down to a similar pressure level as used in a Leak Back Test.

Harbor Freight sells a compression testing kit; they were around $30 but that was last years price.

I do not know how you would hook it up but one of those 12 volt tire inflation pump/compressors will put out 250 psi but at a low volume. You can get them for around $20 at Big Lots and maybe Harbor Freight. However they are very noisy. I do not see how someone could listen for a leak with on 3 foot hose. You would need to put on a longer hose.

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84 300D, 82 Volvo 244Gl Diesel