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The addition of the bypass valve allows recirculated
fuel to flow through the filter and back to the engine, as
the illustration to the right shows, thus avoiding engine
starvation. This compensates for fuel flow in very cold
start conditions.
Yet the diagram looks to show fuel from tank mixing with filtered fuel.
What I struggle with is, where is this recirculated fuel coming from?
The 5/16" quick connect on the top of the filter isn't a return from the fuel rails but rather a return from the filter. So if you disconnected that fitting with the engine running, fuel will come through the fitting on the filter, not the line. So fuel isn't returning to the upper filter. The fuel does get recirculated but that doesn't happen until way back on top of the lower filter here:
The return from the engine is the 12MM (blue) fitting at the bottom of the block. From the tech form below "Fuel returns to the fuel conditioning module on port #4 and then if the fuel is warm enough back to the tank. Otherwise if it’s too cold it gets sent right back through the filter to the pump and back to the motor. "
I could be wrong but how I understand this is the fuel is recirculated WAY back at the 10 micron at heaven knows what efficiency lower filter, sent all the way back to the primary filter but if the primary is too cold, the fuel bypasses that filter and is pumped directly into the CP4. So it is recirculated but at 10 microns, not 5.1 microns.
The addition of the bypass valve allows recirculated
fuel to flow through the filter and back to the engine, as
the illustration to the right shows, thus avoiding engine
starvation. This compensates for fuel flow in very cold
start conditions.
Yet the diagram looks to show fuel from tank mixing with filtered fuel.
The way I see it is the bypass valve acts in the same matter as a bypass valve in an oil filter, if the filtering media plugs up (which would open to allow oil to flow to the engine regardless) or in the case of the secondary fuel filter clogs up with gelled fuel, etc and creates a situation where the CP4 wouldn't be fed fuel due to lack of flow, the bypass pops open and allows unfiltered fuel to flow to the CP4.
The way I see it is the bypass valve acts in the same matter as a bypass valve in an oil filter, if the filtering media plugs up (which would open to allow oil to flow to the engine regardless) or in the case of the secondary fuel filter clogs up with gelled fuel, etc and creates a situation where the CP4 wouldn't be fed fuel due to lack of flow, the bypass pops open and allows unfiltered fuel to flow to the CP4.
What I struggle with is, where is this recirculated fuel coming from?
The 5/16" quick connect on the top of the filter isn't a return from the fuel rails but rather a return from the filter. So if you disconnected that fitting with the engine running, fuel will come through the fitting on the filter, not the line. So fuel isn't returning to the upper filter. The fuel does get recirculated but that doesn't happen until way back on top of the lower filter here:
The return from the engine is the 12MM (blue) fitting at the bottom of the block. From the tech form below "Fuel returns to the fuel conditioning module on port #4 and then if the fuel is warm enough back to the tank. Otherwise if it’s too cold it gets sent right back through the filter to the pump and back to the motor. "
I could be wrong but how I understand this is the fuel is recirculated WAY back at the 10 micron at heaven knows what efficiency lower filter, sent all the way back to the primary filter but if the primary is too cold, the fuel bypasses that filter and is pumped directly into the CP4. So it is recirculated but at 10 microns, not 5.1 microns.
My take
at the engine bay filter…the only recirculation is via the small fitting back to the main fuel return line which only goes back to the tank .
I like that new top design with those reinforcing bars for strength... just wonder if they will do that for the FD4615 set for the 11 to 16s? I will have to take a ride to the dealer and get some pics... interesting. Thanks.
I like that new top design with those reinforcing bars for strength... just wonder if they will do that for the FD4615 set for the 11 to 16s? I will have to take a ride to the dealer and get some pics... interesting. Thanks.
You mean to reinforce the tops of my secondary filter in the FD4615 sets I have? I have one left I believe from the big order I made in the past from dieselfiltersonline....
I bought a five pack of FD46s from overstockdirect.com. So I'm rocking what I've got...
I just put a secondary filter in my 15 and can’t get it to seat properly, even after filing off some rough edges. At least I got it far enough in to connect the lines and it seems to be working correctly. It’s a motorcraft from Rockauto so I’m assuming it’s not a fake.
I just put a secondary filter in my 15 and can’t get it to seat properly, even after filing off some rough edges. At least I got it far enough in to connect the lines and it seems to be working correctly. It’s a motorcraft from Rockauto so I’m assuming it’s not a fake.
When I installed my S&S disaster kit, I could not remove the filter cup that holds the secondary filter, because it needs to removed for the upper piece of intake manifold to be removed from its position but the front cup mount bolt just spun in the hole... so I improvised and cut a big chunk out of the housing. So now my filter just sits in there, unlocked, and spins but it's not going anywhere. As long as it's mostly in there, I wouldn't sweat it. If you were really worried, you could probably cable tie it to the housing (cup) by wrapping it around the top to bottom. .
Last edited by Overkill2; Oct 27, 2024 at 06:30 PM.
Reason: edit comment
Yeah the new upper filter is beefier. When I get 15k miles on it I'm going to cut it open and compare it to the previous revision filter which I kept on the shelf just waiting. Should be interesting.
Yeah the new upper filter is beefier. When I get 15k miles on it I'm going to cut it open and compare it to the previous revision filter which I kept on the shelf just waiting. Should be interesting.
Looking forward to actually seeing the difference.
That will be illuminating... cause I found my 4625 underwhelming....
I don't think you find a difference in the filter media, but will find the added pressure differential check valve in the bottom of that filter and maybe thicker molded material on top with those ribs molded in.
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