Knock, Knock......

[Chatolue]

What in the h--- causes cackle? Have 2000 7.3 PSD with a Tommyknocker inside of it! Any info appreciated. -mad

 

[CHPMustang]

What in the h--- causes cackle? Have 2000 7.3 PSD with a Tommyknocker inside of it! Any info appreciated. -mad

Welcome to SDD Chatolue

I usually blame it on too much air getting to the injectors,not enough lubrication properties in the fuel or not enough fuel pressure to the injectors.

Bill

 

[kenh]

The things seem to have an endless variety of noises to entertain the owner.
Come to think of it, my idle knock has been gone for a couple of years now. (Not that I miss it)

 

[powerboatr]

best thing I did for my 7.3 was to install a regulator that flowed all the unused fuel out of the heads and it really cut down the air in the fuel and idle knock.
I can guide you on what you need and where to get teh pieces, but cant reco. a dealer of a prepackaged setup. its to easy to build your own and to your desires.
takes about three hours to do it right and about 20 minutes to remove if needed
Robert

What in the h--- causes cackle? Have 2000 7.3 PSD with a Tommyknocker inside of it! Any info appreciated. -mad

 

[95_stroker]

Have you tried a fuel conditioner yet? Power Service or Stanadyne are good brands, sounds silly, but it might help.

 

[Car_nut57]

What in the h--- causes cackle? Have 2000 7.3 PSD with a Tommyknocker inside of it! Any info appreciated. -mad

Check the type and level of the oil. Using the wrong oil or running it low can cause all kinds of funny noises.

 

[Chatolue]

Knock,Knock

Thanks to all for the suggestions, I'll check into these and hopefully weed out the little sucker...... Also, do you suppose a small exhaust leak would make this type of noise. I know, get under there and tighten it! Waiting for the sun to go down so my back wont fry. 108 in the shade ain't bad.

 

[Hoss 350]

What in the h--- causes cackle? Have 2000 7.3 PSD with a Tommyknocker inside of it! Any info appreciated. -mad

What in the h--- causes cackle? Have 2000 7.3 PSD with a Tommyknocker inside of it! Any info appreciated. -mad

There are many different causes to many different noises in these engines. They are VERY noisy (not necessarily loud, but NOISY).

To answer your question, cackle in it's truest form is caused by fuel starvation to the number 8 injector, which is caused by it's firing order being right behind that of it's nearest neighbor, number 6.

This fuel starvation can be GREATLY exacerbated by air intrusion into the fuel system. Almost ALL 99-03 7.3 liter engines have quick disconnect fittings in the fuel system before the pump. These fittings, while great in a positive pressure situation, do very poorly in a negative suction setup, (as it is pre-pump in our trucks) which allows air into the system. Also, there are rolled ends on metal fittings that create pressure changes (like a nozzle) in the system, which also free up entrained air in the diesel. Additionally, inside the tank, there is a mixing valve that recycles the foamy return fuel directly into the supply pickup, and a "duckbill" nozzle on the side of the pickup that is designed to allow the truck to continue running if the main pickup clogs, but passes air into the pickup once it is below the fuel level in the tank (about 1/4 tank and below). Is your truck and the cackle louder after the tank is below 1/4 tank? This is why...

There is also one more source for air in the fuel system, and that is the spit-back from the split-shot injectors. During the pause between "shots", the split shot injectors "regurgitate" diesel back into the fuel rails at about 23,000 psi, which, as you can imagine, causes a huge amount of foam in the rails.

All of this air intrusion would not be such a big deal if one of the following two things were to happen:

1.) The pump pushes the diesel into the fuel rails at or above the miscibility point of the fuel (the pressure at which the air "dissolves" back into the fuel, and goes into solution). This occurs in a Common-rail diesel, but not in our HEUI systems. These only pump about 55 psi stock, so the air bubbles do not dissolve.

2.) The heads had a return system that constantly flowed fuel through the heads, creating a situation where air bubbles just flow throught he heads and return to the tank. This does not happen with the "dead end" fuel rails in the heads of 99-03 7.3's.

So what does all of this mean??? First of all, the air MUST go through your injectors once in the fuel rails. This can score/damage your injectors. Second, since there is air in the injector, there is no real way to accurately control the injection timing on the engine, resulting in reduced efficiency due to delayed timing, and NOISE!!! Why does air delay timing? Have you ever turned on a hose that is full of air? How long until water came out? How long until the water was a steady, full stream instead of a spurty, misty crap? Third, injector #8 starves for fuel, because it is at the end of the rail, right after #6 which fires before it. The result? Noise, injector damage, and cackle.

I went through my fuel system from the tank to the pump and replaced it in it's entirety with new parts that do not allow air into the system. I put a pre-pump filter and water separator on my truck, and i plan to install a regulated return off of the heads to finally return the fuel system to what it should be, and what Navistar intended it to be.

 

[whatabudro]

he's new but very whitty. I like him. Thanks for the lesson Hoss

 

[BIG JOE]

he's new but very whitty. I like him. Thanks for the lesson Hoss

Yes, I agree !!! Thanks Hoss. Very well said, but in Down to Earth language.
(even I understood)

JOE