Ok, rewind to just before Thanksgiving. I loaded Marlene with wife, dogs and daggone near straight WVO and drove 200+ miles to Dickinson for Turkey with Dad and Stepmom. Temps were mild (not cold) but, I did run the fuel heater all the way...no plugging or solidification issues with the WVO. For the return, I topped off with diesel (7-8 gallons) and returned home.

Pretty soon after the return, I began to notice a slight nailing at drifting throttle settings and med-high rpm (2800 rpm) if the car wasn't fully warmed up or hot. The nailing gradually became worse as the ambient temperature dropped approacing the Xmas holidays. By the week before Xmas, it was bad enough that I was beginning to think something was loose under the valve cover.

Also, because of the suddenly emerging fungus problem with the 300D, I'd been running straight diesel since the return from Dickinson. Consequently, I haven't been heating the fuel when driving (it had also blown a fuse).

Anyway, the nailing seemed to be getting more and more prevalent until last weekend when, I replaced the fuel heater fuse and got the heater working. I ran around for a couple of days with the heater operating to see if it was going to pop this fuse and suddenly realized that the nailing had ceased.

No nailing at all, with or without the heater now. Granted, the ambient temps have been ultra mild (50°F at night, mid 60s day). Today, the weather has turned to crap again and we're in for some low temps for the next few days. I'll see if the nail returns.

Any observations? Comments?

__________________
Never a dull moment at Berry Hill Farm.

I have a couple injectors that pop off at a much lower pressure than specified. I can hear them when I run diesel in cold weather until the engine heats up. Maybe you had one that was held open by some fat that dissolved after you got the heater working again? Far fetched but the only explanation I can think of.

I thought that too but my heater is only 140-160°F and on further investigation using a non-contact thermometer, I've measured temps of approx 200°F at the injector/head connection.

The acid test will be the next couple of days; the ambients are predicted to drop into the 30's...so, if it is truly cold weather related, the noise should start up again.

__________________
Never a dull moment at Berry Hill Farm.

Any ideas on which cylinder it was/might have been?
My #1, for some odd reason, loves to nail. I think it has something to do with the EGR favoring that end the past 265k of its life...(not anymore

Was it one cylinder or was it sounding like multiples?
Could be a lot of things, but luckily it sounds like the problem has passed you by for now

....for now

That truck carrying the dirty fuel must have stopped at more than one station I see.

I encountered the same thing over the holidays and it took 2 cans of diesel purge to finally stop the nailing. I'm thinking of using an ultra-sonic cleaner.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

OK, so today the ambients are in the low 40°F and the nailing has returned, not as bad, but it is definitely temperature related. Running the fuel heater did seem to help reduce the nailing quicker.

__________________
Never a dull moment at Berry Hill Farm.

Pardon a question from a non-Dieselhead that's willing to learn.
What's nailing? Is it anything like preignition/detonation in a gas engine? what would cause it? Fuel getting into a cylinder too early?

__________________
Norm in NJ
Next oil change at 230,000miles

Lots written in here about nailing but, basically it is when fuel is introduced to the cylinder prematurely during the compression stroke (leaking injector et al) and some combustion takes place. Sounds like a hammer hitting a nail into hardwood.

__________________
Never a dull moment at Berry Hill Farm.