As I said, on my engine the RPMs don't affect the level of clatter. It is constant when driving, regardless of speed or RPMs, unless I let off the throttle to coast. Then there is no clatter. If I put in in neutral there is no clatter regardless of RPMs.
It sounds like you are saying that some clatter is normal under load but if the timing is off then there will be more clatter at higher RPMs. Am I reading that right?
And while we're talking clatter, what is the source of the clatter?
Does it sound like this: [LOUD AND NOISY CLATTER like the pistons are hollow steel, sealed at the bottom and with a 1/2 inch steel ball from a ball bearing sealed inside and rattling inside each piston as the engine runs.] (that's normal)
I live alone in an almost
completely silent environment, almost 24/7 with just the noise of typing on my keyboard now and then. I don't have a TV. My radio hasn't been turned on in years. Occasionally I watch a streaming sporting event or documentary / youtube video on my computer BUT I DO NOT LIKE NOISE, I LIKE PEACE AND QUIET.
Relative to my normal extremely quiet environment: when my truck is running it's similar to the description I gave above,
loud and noisy clatter.
Simple explanation: To start with, these engines are an older style MECHANICAL Indirect Injection DIESEL and they naturally have a loud clatter. THE CLATTER comes from inside of the MECHANICAL injectors and some from the detonation or the slight
pre-detonation of the fuel which is relative to
injection pump timing which is determined by the detonation characteristics (cetane levels in diesel fuel for example) of the fuel. The injector noise and detonation (pre-detonation) noises transfer from the injectors and cylinder liners through the heads and block and into the air, probably loudest close to the injectors.
The clatter noise from the injectors originates from inside of each injector, more specifically from a moving spring loaded and pressure driven solid steel 'piston' with a pintle needle at the bottom which seats the needle in the nozzle ( fuel can only spray out when it is open, otherwise it's sealed) as well as seating the piston in the larger bore of the injector body.
The pressurized fuel from the Injection Pump (IP) enters a chamber inside the injector and when it reaches the injector's design pressure ("pop pressure") it moves the piston back against a very strong spring and at a specific position of the piston it releases the fuel in that pressure chamber down through the nozzle, exiting in a spray pattern. The release of the pressure causeds that piston and pintle to slam into the seat to seal the injector to repeat the same cycle when the rotary injection pump sends the next burst of fuel through that line to the that injector. The combination of the mechanical noise of the injector and the detonation timing noise is generally referred to as "Injector Noise"
That noise can become
ABNORMALLY LOUD (seriously LOUD) when injector(s) are worn out.
I bought an 82 Datsun King Cab with a 4 cylinder NISSAN SD22 Diesel (IDI) with about 325,000 miles on it with original injectors, all of them worn out and each one sounded like a piston rod breaking through the block. It was also blowing a
gigantic cloud of mostly white smoke. I put new injectors in it AND IT RAN LIKE A WATCH. I loved THAT diesel truck more than any other diesel I've ever owned or driven.
Anyway here is a video that should help you to understand these mechanical injectors. Listen carefully when he does the pop test and you'll hear a metallic 'clank' instantly after the spray release. That's the internal piston and pintle needle seating with pressure from the internal spring, (after the fuel pressure is released). See my notes after the video
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NOTE: Excessive volume (decibels) of the noise could be from one or more worn out injectors, especially if accompanied by a lot of white smoke.
Alternatively it could be due to timing that is too far advanced.
It would be a good idea to have all of your injectors pop tested and decide whether to rebuild them or buy new ones.
One thing puzzles me about your truck. You said it only makes noise under load, and like 'no noise' otherwise. I think mine is loud all the time, it does get quieter when I am driving it though, and no smoke on start up, warm up or driving unless I try to push more fuel through the engine than it can efficiently burn. Diesel vehicles are NOT supposed to be driven like gas vehicles. When you need to accelerate you don't tromp the accelerator through the floor or you'll just blow a lot of black smoke waste fuel and make people want the government to confiscate our trucks and crush them.
Ideally don't give it much more fuel than it can efficiently burn. If you want a hot rod truck, buy a gas engine truck.
That being said, I KNOW there are times when we are compelled by circumstances to over fuel the engines too eek out a little bit more horsepower and torque, like to get over the top of that steep grade when working the truck with a sizeable load.
IP Timing for these IDI trucks and vans using modern at the pump diesel fuel should probably be between 9.0 degrees and 9.5 degrees BTDC. Not the original factory 8.5 degrees BTDC and the reason is due to the differences in detonation characteristics of modern Ultra Low Sulfur Diesel fuel and the old high sulfur fuel at the time these IDI trucks/engines were designed and built.
those timing numbers were figured out by some old timers in these forums who had A LOT OF EXPERIENCE working on these trucks and timing these engines and the detonation characteristics of low sulfur and ultra low sulfur fuel were taken into consideration.
TODAY with all of the "who knows what" biofuels are being added to ULSD it's hard to know exactly where to time them but I'm going to use those numbers to start with. NOT 8.5 deg. BTDC
I seem to recall reading that as these engines get more wear, higher miles, the timing needs to be set more advanced.
I'm just trying to figure out if this is just what NA IDIs sound like normally or if I should stop driving it until I can afford timing equipment.
NO ONE HERE (that I know of) HAS HEARD YOUR TRUCK RUN, BRIAN so how could we know???
You wrote that you would post a video.
