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Discussion Starter #1
A service adviser told me that the CP4 return path flow had been changed in 2017 to route it back to the tank so that metal particles would have to go through filters again before getting to the injectors. This would be similar to what the S&S Diesel Bypass kit does. But S&S still seems to be marketing their kit for 2017+. Can anyone confirm or deny a change in CP4 fuel routing for 2017+?
Thanks.
 

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I have not seen ANY documentation from Ford or Bosch regarding changes or revisions to the CP4 HPFP in the 6.7L Power Stroke as of this date. The fact that this continues to be discussed tells me there likely aren't any?

Just in case there are misconceptions about fuel flow and return with regard to the Ford Super Duty trucks I can tell you by the service documentation, description and operation, nothing has changed. The return fuel from the high pressure fuel injection pump combines with the return fuel from the fuel rail and is routed to the fuel cooler and then to the diesel fuel conditioning module. (primary filter) Inside the module there is a thermo-recirculation valve that depending on temperature of the fuel will recirculate the returned fuel either to the primary filter or back into the tank.

The only things that I can tell you that HAVE changed in 2017 Super Duty's with 6.7L Power Stroke engines are in the low pressure fuel system. The low pressure fuel pump has been moved from the fuel conditioning module to the fuel tank and the fuel conditioning module with filter is all new.
 

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So, just to clarify... If the CP4 implodes, the particles will have to go thru the primary filter to get to the injectors or be flushed into the tank based on fuel temperature?
 

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So, just to clarify... If the CP4 implodes, the particles will have to go thru the primary filter to get to the injectors or be flushed into the tank based on fuel temperature?
No. We were discussing fuel return flow to the tank.

The problem with the CP4 contaminating the entire high pressure fuel system is due to how fuel flows once it enters the pump. Fuel enters the main body of the pump where it lubricates and cools the cam, followers and pumping elements. From there fuel is sent to the high pressure cylinders through the volume control valve. So any debris created from the cam, followers and pistons that makes it's way past the screens on the VCV heads directly to the fuel rails and then the injectors. The unused fuel returns as previously described.

This explains why removing the VCV from the pump for contamination is needed to verify pump failure.
 

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Ahh, ok. I had a euro diesel car fail in this way and was only hoping that there was some safety measures to prevent that my this truck.

My tdi is also prone to this failure...
 

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There is a website that sells a "bypass" kit that blocks off the fuel feed to the VCV from the inner pump and takes clean fuel from the filter piped in from the current inlet connection. Looks like it works but I personally can't endorse it because I have no experience with it.

I think these are the peeps that came up with it: https://ssdiesel.com/shop/ford/kits-ford/ford-6-7-cp4-2-bypass-kit-2011/

And the Learn How It Works link WITH DIAGRAMS! ;) https://www.drivingline.com/articles/new-product-spotlight-ss-diesel-motorsport-s-cp42-bypass-kit/


I have seen it for sale on other websites.
 

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Discussion Starter #9
Yes, the aftermarket bypass kit is what I mentioned in my original post. S&S Diesel makes it and others sell it. It sounds like Ford has not incorporated a return path change. Thanks to Ford_Doctor for the information.
 

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Well the thing is the pump is not Ford's, it is Bosch. I think that if this truly is going to reduce or eliminate contaminating the rest of the high pressure system a design change would be fairly easy to implement. One could debate that making the pump more robust or resistant to suspended water would be more prudent but then again, keeping water and other things out of the fuel to begin plays a big part.
 

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I realize this isn’t feasible for most, but for my Audi I purchase fuel in a separate tank. I treat it with Optilube lubricity additive. I then run it through a 2 micron filter and then a Goldenrod water absorbing filter. Then it goes in the car. Easier to do when you get 40 mpg and only drive it on the weekend.


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I've found that the DieselSite insurance plan along with getting fuel from quality stations, then adding a quality fuel additive have done wonders for me. I run 10 micron filters in the DieselSite kit, Howe's fuel products, and in recent months only using Shell fuel. I'm QUITE happy with the results across the board.

It's not a single focused issue of water in the fuel, but the lubrication properties of ULSD. I'm sure you understand how running crappy oil in your motor causes problems you can understand the problem of poor fuel lubricating the inside of the HPFP.
 

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Discussion Starter #15
As said above, it's not just water, but gasoline, ethanol, methanol, etc. can also have the same effect of reducing lubricity in a fuel that is already low in lubricity. I have read on the internet (so it's true) that Canadian fuel is higher in lubricity. I have run Ford Cetane Booster and Performance Improver PM-22A since my truck was new. It adds lubricity and may also act as a demulsifier. Demulsification is important to separate any water into droplets that can be removed by the primary filter. Because alcohol is a problem I would avoid ANY fuel product that even hints about alcohol. But, the most important thing that I do is always, always, always, get a receipt for every tank of fuel. That way I can go back on the fuel station insurance if the pump tears up and furl analysis shows contamination. I am also considering switching to the more expensive Opti-lube product which is very well regarded.

Thanks again for all comments.
 

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Neither Motorcraft diesel fuel additive PM-22 or PM-23 have demulsifying capability. According to the literature I can find there is no mention of it, just lubricity, Cetane and anti-gel. This is why I recommend Stanadyne Performance Formula.
 

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I think Stanadyne is the only all in one, that I found so far, that mentions removing water. It is a bit on the pricey side compared to the others, but if it does indeed remove water, then it is worth it. Right now I use power Service Diesel Kleen. Their Clear-Diesel removes water and slime, and the Diesel 911 removes water and prevents gelling and fuel filter icing. None of these are all in one products though. Diesel Kleen is like a summer blend, Clear-Diesel is just a tank cleaner, and Diesel 911 is the winter blend without Cetane boost. One could mix Kleen and 911 to get what Stanadyne gives, but by then, it would cost the same, but it is easier to find the Power Service products. I haven't found Stanadyne locally, yet.

I am on my second fill since I got my truck (third tank) and I put the recommended amount of Diesel Kleen in for 26 gallons on this last tank and already notice an improvement. Engine is running smoother.
 

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I'm not helping with this rabbit hole, but I really like Schaeffer Oil's Dieseltreat 2000. Now, I have not ran it in my truck, but my other two older diesels get it every tank. If you wanted to research it: https://www.schaefferoil.com/fuel-additives.html.
A. It's affordable if you buy it by the gallon when you break it down per tank-full.
B. It requires far less volume to treat each tank as well. ( I use old Stabil fuel treatment bottle to dispense). 1oz treats 15 gal.
C. You can buy it from Amazon.
 
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