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6.4 Fuel System

32K views 9 replies 7 participants last post by  B585Ford 
#1 · (Edited)
I tried to add this to the General 6.4 Modifications thread, but the first post became too long, so with the help of B585Ford, here is a quick and dirty description of the fuel system (and if you see anything wrong or if you have any information to help us all out let me know and I'll add it/change it).



It is probably beneficial to get a brief knowledge of the 6.4 fuel system. The fuel system on the 6.4 is pretty complicated. For anyone wanting to look at the schematics, here is a link:




Basically the fuel system operates like this: Tank to the water separator and low pressure pump (LPFP) including the 10 micron filter. There is no return at the LPFP. Fuel goes from the LPFP to the fuel bowl (location of the 4 micron filter in the engine bay). The fuel bowl has a spring valve that opens at 3 PSI. When that valve opens, it sends fuel back to the tank. The fuel bowl does supply fuel directly to High Pressure Fuel Pump (HPFP). The HPFP controls rail pressure (RP) by the use of 2 valves. There is the Pressure Control Valve (PCV) and the Volume Control Valve (VCV). Whatever fuel that is not sent to the rails from the HPFP goes to the fuel cooler. Also, any fuel that goes through the rails but doesn’t get injected passes through a banjo bolt and then “T”s into the fuel cooler line (with a 1-way valve). After the fuel passes through the fuel cooler it goes back to fuel bowl. That fuel mixes with intake fuel (from the tank) in the bowl. Again, once the pressure in the fuel bowl gets up to 3 PSI, the valve in the fuel bowl opens allows it to return to the tank. Essentially, this creates a pretty constant 3 PSI inlet pressure on the HPFP. (This is straight from the 6.4 Bible)



Important Facts:

1. The HPFP on the 6.4 is called the K16. It was built by Siemens. Unfortunately, since this engine has been discontinued by Ford, it is pretty much impossible to get a new HPFP. If you have to replace your K16, you will be getting a reman and the quality control on the remans has been less than optimal. Try to protect HPFP at all costs….i.e. DON’T SKIMP ON THE MAINTENANCE OF THE FUEL SYSTEM!!!!

2. This system is regulated by the return. It is NOT regulated by the supply. In other words, LPFP does nothing to regulate the inlet pressure to HPFP.

3. The desired HPFP inlet pressure is low compared to most HPFP (about 3 PSI).

4. The HPFP controls RP with the use of 2 different valves (PCV and VCV). The CP3s on Duramax’s and Cummins only use 1 valve. The HPFP is very effective at controlling RP when receiving significant variations in the quantity of fuel. That is definitely one of the strong points of the HPFP.

5. The K16 flows more fuel than any other HPFP that has been made to date for pickup trucks. It outflows the CP3 of the same era by approximately 20% and CP4s in the new Powerstrokes and Duramax’s by even more (hence why the new 6.7 Powerstrokes are running out of fuel above 500HP). Translation, you have enough fuel from the stock components of fuel system to make up to 650-700rwHP without upgrading anything on the fuel side!!! Of course, to see 700 RWHP, you would need to do a number of air upgrades.



FLAWS:

1. By far, the biggest flaw in this system is poor water separating abilities of the LP system. It gets less effective as water collects in the LP water separator. Almost everyone agrees this is the single biggest reason why we see the K16s fail. The K16s also seem to be a little more susceptible to being damaged by water in the fuel compared to CP3s.

2. The drain valve for the water separator is prone to building up deposits. When enough deposits build up, the water separator will drain poorly (if at all) which makes the poor water separating abilities of the LPFP that much worse.

3. The K16 also seems to more susceptible to damage from bad fuel than a CP3.

4. The factory system does not have any sensors in the LP system so your truck’s computer has no way of knowing what pressure your LPFP is supplying. Although this typically isn’t a problem, if your LPFP is getting weak and not supplying the HPFP with adequate fuel, you won’t know it until the lack of inlet pressure on the HPFP is severe enough to cause symptoms (typically surging or loss of RP). The HPFP can be easily damaged when it staves for fuel.



Recommendations for keeping your fuel system healthy

1. MAINTENANCE, MAINTENANCE, MAINTENANCE!!! I can’t stress this one enough. Change your fuel filters on a regular basis (more often than Ford’s recommendation if you have a stock LP system). Drain your water separator at least once a month or every 2,000 miles (whichever comes first).

2. Try to always buy fuel at busy locations where you know the quality of the fuel.

3. Strongly consider upgrading your LP fuel system. You will not gain any performance from an otherwise stock fuel system, but it can save you some major repairs.

4. If you are installing a LP system, I highly suggest installing a gauge within that system so you can monitor your LP Fuel Pressure. This will help you diagnose a weak LPFP before it damages your HPFP and it can be helpful if you ever run into problems with your fuel system. Fuel system problems can be very difficult to diagnose what exactly is causing the problem.
 
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#2 ·
Thanks for all your time/words, I've pretty much followed your thread recommendation since joining (-) a few mods like this fuel system but will attend to them soon. Appreciate your time, thanks again. Jayson
 
#4 ·
Tyler,

I found 2 mistakes that I made (at least that I noticed so far). First, in the "Important Facts" section on #5, it "650700rwHP". It should read "650-700 RWHP". The second one is in the "Flaws" section on #4. It says "(typically surging)", but it should read "(typically surging or loss of RP)".
 
#6 ·
excellent thread!!

I have gone WAY over board with protecting my system...

I installed an 80ga transfer tank in the bed (also extending my range to around 2200miles) :) that transfers to the main tank via an additional AirDog150+additional water separator.. they are initiated with two of the upfitter switches... one switch turns on the pump, another tosses power to a normally closed 12vdc solenoid valve which is on a timer board (auto shutoff) at 1/2 tank of fuel.. I can flip the pump switch and NOT flip the solenoid valve, and polish the fuel whilst I'm driving down the road... I only fill the truck through the transfer tank, and any fuel that reaches the rails has been scrubbed at nine times.....

word of caution about doing something similar: you don't want that fuel 'too' polished... 500ppm, you can polish all you want- but 15ppm you better stop before too long, because it's much dryer (in terms of lubricity) and will clump... a clump isn't something you want to shove through your HPFP..
 
#7 ·
Awesome job Tyler and Brett. Great thread! :thumb:
 
#10 ·
That's not true....if anyone finds anything that is incorrect, Tyler was responsible for that!!!! :funny::funny:
 
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