Ford's answers to the NHTSA 6.7 Investigation
There was a request for a link to Ford's answer's to the NHTSA investigation posted on a previous thread, since closed. Here is the link: Ford's NHTSA Answers to the 6.7 investigation This PDF i...
Forum Discussion
NinerBikes wrote:
I need to know from someone that knows the "inside" scoop.
Is the fuel metering valve "always open" a bit?
Looking at the design, I would guess it cannot be ever completely closed, as that would create a vacuum as the piston is forced down by the spring --- unless the valve to common rail leaks a bit, or the piston leaks around the bore.
What if something plugged the micro filter (already mentioned).
Even if it is not a vacuum, pressures in there can be sharply lower on the "intake" stroke, and with lower pressures, (or delta p), components of the fuel can boil, and then collapse either on the compression stroke (cavitation bubbles).
The question is... is the failure in the High pressure piston?
Or could it be the vacuum is just strong enough to prevent the spring from returning the piston and maintaining contact?
That would result in cam / roller / piston shock impact, that is limited not by the strength of the DLC, but the underlying material.
