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I looked at the gasket yesterday and it was a bit "flat". There was a small section the gasket was not smooth.
So I will replace it and see how that goes.
Originally you could buy the gasket only, then they made it into a package deal with extra pads, inflating the parts. Most times you only need the gasket.
For bleeding out the air and priming the fuel, I plan to use this method here, which basically give power to a connector wire (pink and black wire) on the front passenger side's kick panel (starting at around 43 seconds in):
When I run a hose from the bottom front to a fuel bucket and the bottom rear also to the same fuel bucket, there are lots of bubbles coming out (bottom front). I then run the top front (one coming back from the secondary filter) to the same bucket (cap the top left, going back to the fuel tank), there are very few tiny bubbles.
So I suppose the air leaks internally from the top compartment of the cap (return fuel area) to the low pressure inside the filter.
It doesn't look like the new gasket fails here since the high pressure is in the 2nd top compartment. That would prevent air traveling down from 1st top compartment. The 3rd compartment from top is the inlet fuel and the bottom is the water release valve.
So by reasoning, the air path must travel into that odd valve on top. The one with the brass and spring and plastic cap. Those do not have rubber ring, so I suppose they are not air tight and designed for air to leak. I don't know how this part of the HFCM works.
Would someone please explain how that top compartment of the cap works? Maybe my thinking is wrong somewhere.
Any guide or more information about how this HFCM work or troubleshooting guide would be great.
Watching some bubble test where they use the key to raise the fuel level in the secondary filter bowl, there is no air bubble at all.
I took out the pump again and study inside the aluminum cap.
The top compartment has a black plastic with a valve. It has 2 springs, one strong, one weak. Usually that's for controlling purposes. I don't know the purpose of the strong spring. The weak/small inside spring opens up the plastic valve. I think that's for the scenario when return flow pressure is too high and somehow the 1/4" tube can't handle it, it would overflow into the filter chamber. That would prevent pump damage.
The copper stick inside is not a valve. There are two lines openings on the side of the circular hole, so the gaps will allow anything to go in. In another word, that copper stick doesn't prevent anything from moving in or out.
Furthermore, my black plastic cover has a 1/4" hole. That defeat the whole purpose of the plastic valve. That would allow air to go back in circular motion as I experienced, especially the inside filter housing has lower pressure than elsewhere.
My thinking at this point is that this must be missing a piece. Maybe a rubber plug for that 1/4" hole. I think if I plug it up, everything will work. But ...
I need to see pictures of a good working one. My current searches didn't give me much.
There is an image here I found, that little hole inside the black plastic cover, at the top right corner has nothing covering it:
According to the following diagram, that is a thermo valve (DTRM). That probably means the large spring would "shrink" when cold to open up the flow so that very thick diesel fuel would flow back into the filter (recirculation).
However, that hole on top would open up a path that defeat the whole purpose of pretty much everything, unless ...
It's used to allow "small" amount of fuel to pass by, so that when temperature rises, the large spring would get "updated" temperature. However, that 1/4" hole is very large for this purpose, unless ...
For very cold winter whether, diesel are so dense that a big hole is needed. But ... that design would defeat the whole air release/prime feature. Without the heater element, this valve is further a liability.
12-31-2018, 10:12 AM
