Quote:
Originally Posted by katja
Has anyone referenced here all the possible causes of "nailing"? From what I understand, that annoying sound could be caused by (don't quote me, I'm observing, but don't really know):
-injector nozzles with poor spray pattern (dirty or worn)
-injectors that are sticking/not popping correctly
-air leak (where? supply lines?)
-bad fuel
-pump timing (too advanced? too retarded? I don't know)
-weak injection pump (?)
-excess carbon buildup in pre-chambers (?)
I've been trying to figure out how to tackle a periodic, random nailing I'm hearing....it happens most often under light throttle...goes away under heavy throttle, and not present at warm idle. Somedays it's really bad, other days, barely at all. Diesel purge didn't help, so I'm thinking it's time to replace the injector nozzles, but now I'm wondering if that's REALLY the problem (probably won't hurt though).
|
This is what I think:
I have not understood why yet but apparently some nailing can be caused by too advanced or too retarded IP timing. The Nailing/Knocking sound has to do with too much of the Fuel bruning at the wrong time and or place in the Pre-Combustion chamber.
Burning and the wrong time and place includes most of what you said.
You also left out low/bad compression.
Weak Injection Pump- I am not sure what you mean by this. Worn or abused IPs have erattic fuel delivery and deliver less fuel. I am speaking of the high pressure fuel that goes to the Injectors.
This can be caused by worn Elements/Plungers and Barrels (scratches on the parts due to bad fuel or poor filtration or some alternate fuels) or if the Rollers, Tappets, and Camshaft inside of the IP are worn (the makes the internal timing of the IP).
[On other vehicles with Rotary type Fuel Injection Pumps (like VW Rabbits, my Volvo and vehicles with Standyne IPs) the advance mecanism is built into the Fuel Injection Pump and as the pump wears the advance become retarded over time. The advance pistons are also at the bottom of the IP and that is where any water will also settle. If the water sits long enough the advance piston can stick.]
Aparrently on those IPs with O-rings that leak; when they leak it some time causes nailing (from what I have read in the threads).
Quite a few members have reported that after the O-ring changing job they experienced Nailing until they have driven 200 miles or so. The reason for this has yet to be explained.
I am not sure if a weak Fuel Supply pump will cause Nailing or not. I guess with the OP saying it was his filter there could be something but it is not clear to me what it is.
I have not read of the excessive Carbon explination for Nailing. I would be the result of another problem or problems like Oil burning, bad Injector Nozzle, Ball Ping damaged, damaged Pre-chamber, bad fuel and so on.