My 2.5 turbo has a loud clatter on one or two of the cylinders. If I crack open the injector line on the cylinder in the middle of the engine most of the clatter goes away. It is only noisy at idle and partial throttle.

Does this sound like low compression or a bad injector?

Diesel knock can almost sound metallic and fool some people into thinking it is mechanical.

Tasma,

Your problem is usually a bad injector. Switch the suspect injector with one that is good and see if the noise follows the suspected injector.

It the clatter moves with the injector, get that injector rebuilt at a Diesel injection shop. You should do this ASAP because the knocking is hard on the engine. Its actually trying to fire backwards on that one cylinder.

The same thing has happened to me and replacing the injector always fixed the problem. I always have extra injectors from used engines so I just replaced the injector with another one.

I don't see how low compression could cause clatter. If the compression was low enough in one cylinder, that cylinder would misfire not knock. The knock is usually caused by a leaking injector that isn't waiting long enough to pop open and inject, thus the fuel gets into the cylinder before the piston is near TDC. Its sort of like preignition in a gasoline engine when using gasoline that does not have a high enough octane rating.

P E H

I have a wrecked 240D without many miles on it. Would the injectors in it be like the ones in the 1991 2.5 turbo? They want $50 each to check and repair the injectors at the Bosch service center in town. I am thinking it would be good to have them all checked.

I would suspect a bad injector, but before I did anything else, I'd run a full bottle of RedLine injector cleaner/fuel treatment in it. If the knock goes away, then comes back after you fill with plain fuel, get it rebuilt. If it goes away and stays away, you need to drive it harder or longer, it's carboning up from slow running.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I replaced a 5 injectors on my TD and it still knocks hard at all ranges and loads. Could this be the IP, timing, or something else?

I moved the bad injector to the front cylinder and the noise followed with it. I took the injector down to the Bosch service place in town and they said the injector was good. Evidently their simple test setup doesn't test all aspects of an injector. I ordered a new tip for the injector ($50) and have them rebuild the unit.

I wonder how many people have been told their engines needed to be rebuilt by dealers when the only problem was injectors.

I put in the new injector and the same problem is there.
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Tasma,

That is very strange. Are you sure you got the correct injector rebuilt? If the knocking moves with the injector, I don't see how it could be anything else than the injector.

P E H

I am going to take out a good injector and take it to the Diesel service shop along with the one they rebuilt. I suspect that the lift pressure is not correct and they didn't pay close enough attention.

Tasma:

If you also have a rough idle and low power until the turbo kicks in, consider a leaking pressure valve holder seal on the injection pump. I got quite a deal on the 300D because it had several that leaked -- no power at all on #4 and #2 and #3 where low -- shook like crazy.

I replaced the pressure valve seals (the pressure valve holders are what the injection lines screw down to on the IP) and completely fixed the problem.

Not impossible, especially if you had the 0-rings on the pressure valve holders replaced recently to fix a leak.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I had the bad injector tested along with a good one. The good one is injecting a 2025 PSI and the one that makes noise is at 1975 PSI . They said that it is in spec and it wouldn't cause problems. I Don't know what else to do.
They were more than glad to charge me money and not solve the problem.

Tasma,

Sorry, I don't know what your problem is

Can you get a complete used injector someplace and try that?

Maybe some one here on this web site has an extra one they would loan you and sell if it works OK.

P E H

Either the spray pattern is bad or you have something else going on.

Can't be a pressure valve seal leaking if the knock moved with the injector, must be the injector.

I'd still try a bottle of RedLine in a tank of fuel before getting too worried, it tends to cure all sorts of ills, at least for a while.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I bought a half gallon of Stanadyne fuel treatment and loaded the tank up with a double dose. Seems to help a little.


I will check e-bay to see if any injectors show up there.

The people on this forum should form a "virtual junkyard"

I agree with P.E.Haiges and the drippy injector as the knock followed the injector. I'd consider looking for another shop, and I have learned (the hard way) to find the crack and opening pressures before heading to the shop with ALL the injectors for the engine. Bosch makes good equipment, but the quality of injector shops varies with the level (years) of experience and cleanliness of the shop. I ask the shop for the pressures before I hand over the injectors. Blank stare or an answer without looking them up means a sloppy shop in my book. And judging the spray pattern quality properly takes experience. I also think that doing one injector at a time is dangerous: the injectors need to crack and open within a range of pressures found in the book AND relative to the rest of the injectors in the engine. Being a fuel fanatic saves a lot of future time and money dealing with injectors and glow plugs.

__________________
daBenz - 1970 220D