An Editorial by dieselmann
Volume 14; November 02: The Dreaded Cackle
I hate kicking over this ant hill, but there has been so many questions, discussions and rumors over the cackle issue, I felt that I had to post something addressing this. The problem with the "cackle", there are various things that can cause a cackle--just as there are various things that can cause a knock, squeal or vibration.
A cackle is a fuel related problem. It is generally caused by an insufficient fuel to air ratio in the cylinders. This can be caused by low fuel pressure or volume or an injector malfunction. It can also be caused by incorrect injection timing--either too soon or too late. Finally, it can be caused by poor fuel quality, aeration or contamination, which either results in insufficient fuel due to displacement, or changes how the fuel burns in the cylinders, in effect changing the timing by making it burn too slowly or too quickly. This can happen on any diesel.
On the PowerStroke there is also the high pressure oil system to consider. If there is a problem in the HP oil system--too high or too low of pressure, aeration of the oil--it will affect injection timing and the volume of fuel injected into the cylinders.
Ford started having a cackle issue on the PowerStroke engine with the 1996 California emissions engines. This was the first year for the "split-shot" injectors that are used on all PowerStrokes from the 98.5/99 model/years and up. The split-shot injectors give an initial shot of fuel to the cylinders, then injection is briefly interrupted, then a larger shot of fuel is injected. This is to reduce emissions while not sacrificing power by lengthening the burn time of the fuel to make it burn more completely. Unfortunately, it also causes oscillations in the fuel passages in the heads, which resulted in underfueling of the cylinders. This cackle was an intermittent rap at idle or part thottle when the engine was warm. At first and high pressure fuel regulator was tried, then a damper on the lift pump outlet to the heads was added on the 97 model/year. Finally, a revised computer program was released that cured the problem.
In 1999 there were problems with the pressure regulator valve on the new fuel filter housing. The regulator had to be revised a couple of times to get the correct pressure and cure a problem with the valve seal ironed out. This cackle was a rattle or rap under load when the engine was warm.
The last cackle is the one most familar to PowerStroke owners. This is on the 99 and newer engines and is caused by the oscillations resulting from the split-shot injectors combined with the firing order of the engine. #8 injector-the last one on the driver side--is actuated immediately following #6, which is right next to #8. This can reduce the amount of fuel available to the #8 injector and results in an intermittent, irregular rap at low engine speeds when the engine is warm. It can happen anytime, but is more prevalent in high ambient temperatures and at higher altitudes. The fix for this cackle--THE cackle, according to Ford--is to replace the #8 injector with the "long-lead" injector. The long-lead injector has a longer primary or initial shot of fuel to compensate for the underfueling condition cause by #6. To go along with the new injector is a revised computer calibration to prevent a false #8 misfire code during a cylinder contribution test.
THE cackle from #8 cylinder is not detrimental to the life or operation of the engine. Unfortunately, Ford and International just focused on this one specific cause that occurs under specific conditions and released a repair, which is not 100% effective. Part of the ineffectiveness of the repair is due to the various factors that can cause A cackle, but not THE cackle addressed in the bulletin. In short, the engine needs to be diagnosed and everything that could cause A cackle addressed or eliminated before assuming the noise is THE cackle.
Not all engines seem to do it as fuel quality and computer calibration does affect a cackle in general. For example, my 01 Federal emission truck does not do it here in California. The most recent cackle complaint I have seen were six months ago when a customer went to the mountains where he heard the cackle, but it only did it there and not here in the Sacramento Valley--a difference of about 5000 feet in elevation. It's been over two years since I have seen a truck for THE cackle concern. I have looked at trucks that have the characteristic diesel combustion noise, usually new owners of the PowerStroke who want to know if it's supposed to be that noisy.
Depending on the cause A cackle can be an symptom of a problem that may result in engine damage over time. There are also upper engine knocks caused by a mechanical problem that can sound like a cackle, but tend to happen hot and cold and at all engine operating conditions. I have had to replace a piston and rod assembly on an engine that exhibited a cackle-like knock.
Recently there have been various aftermarket fixes developed to cure PowerStroke cackle conditions. Any of them may be effective in correcting a specific cackle, but not necessarilly every one. Just as with the long-lead injector, the cause of the noise must be determined before a repair is attempted. The fuel pressure should always be checked, idealy when the noise occurs. Since there are screens on fuel inlet fittings on the 98.5 and newer heads, fuel pressure needs to be tested at each head passage. If the noise occurs at all engine speeds and/or all operating temperatures, an attempt should be made to isolate the noise to one cylinder by canceling or disconnect each injector while the engine is running. If the noise goes away when an injector is unplugged, then the problem is with that injector or that cylinder (piston, rod assembly). If the noise does not go away, then the cause is something that affects fuel to all cylinders (fuel or oil aeration, fuel quality/contamination, fuel pressure), or a valve train problem. Once it's determined if the noise is coming from one or al of the cylinders, further invstigation is needed to determine if it is a cackle or a mechanical noise. It should be noted that whenever the injectors are removed from the heads, or an oil aeration condition exsists in the high pressure oil passages in the heads, it may cause a cackle that will not go away after the repair until the vehicle is driven in excess of twenty miles.
Charles David Ledger; dieselmann©1999
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