Run Silent, Run .......

[afgunn]

My 93 does a curious good thing, strange I know. When starting cold (yes, I know cold is relative esp. down here where I live) at the same point or same amout of run time regardless of the ambient temperature the diesel IDI clacking suddenly drops noticeably - almost completely quiet. I have been pondering on how this could be and here is my SWAG - it takes X amount of time for the heated fuel to get from the heater bowl to the injectors. Well that is my SWAG, what say you?! My 98 never did this but then I was also told, for other reasons, that the injectors probably needed to be changed.

[DmaxMaverick]

That's the HPCA (Housing Pressure Cold Advance) shutting off. The pump uses fuel pressure in the housing to advance injection timing for cold starts. Once the temp is up, it shuts off, and the engine will get less loud. It has nothing to do with the fuel temp. Only the coolant temp. Your '98 is EFI, and doesn't have an HPCA. The timing is adjusted electronically by the PCM, and is more gradual than a DB2 equipped engine. It is happening on the '98, it is just not as profound.

If your engine is too quiet, read on.....

The fuel temp has very little, if anything, to do with the combustion rattle. If the fuel reaches the cylinder, it's pretty much moot what happens to it after. It's the cylinder and air temp that will effect the rattle. Quiet combustion means too little air (time for an air filter), low compression or retarded timing. It should rattle, at least some. Worn injectors usually cause a heavier knock, but can get quiet if they get fouled (plugged). A plugged fuel filter or failed lift pump can/will retard timing, quieting the rattle, also. If all else checks out, you need to check your injector timing, and timing chain wear. The only thing left is the IP after that.

[afgunn]

Well, so much for my SWAG! I'm guessing the fuel injection is advanced until the engine is warmed up a little.

I do not believe that I have any other problems - runs very smooth and good power, intake filter and lift pump have been replaced, intake has been "opened" up and no knocking. You can still tell that it is a diesel - not as quiet as a DMax. But as I said it is a lot quieter than my 98 was which just goes to confirm that the injectors on the 98 most likely needed to be replaced.