Cleaned HFCM, now losing FP

As the title states. Pulled manifold off, cleaned an enormous amount of crud out of there, put it back together, now I'm dropping FP as you accelerate. Anything over 25% pedal and it drops from 58-59 down to about 51-52. Went wot yesterday briefly, and it immediately dropped to 42 and stabilized. Pump looks original so figured I'd throw on a new one. Same scenario afterwards. Only thing I can think of is I didn't get the DTRM back in correctly. It all fell out when I pulled the manifold. I couldn't get the fuel lines off, so I just rotated the manifold up somewhat out of the way. Was feeling at best trying to get the nipple and spring back in there right.

Which way does all that go back together? Found the Ford image online showing the pieces, but never found anything showing how they actually go back into the HFCM. I figure it's not in there just right, and letting fuel bypass back to the tank instead of back up top where it belongs.

Also when I pull drain plug, fuel continues to run out. Like, the housing drains quick, then it drops to a small flow, but stays constant. Don't quite understand that one, unless it's draining the upper filter housing that slowly. But is that even possible?


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Anybody at all?


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Ok.....so, I took another stab at this thing today. Got the lines off and pulled the hfcm completely off the truck where I could actually see what I was doing. The spring/nipple are back in correctly now...I'm positive of that. Still dropping pressure. Doesn't seem to be as bad or as quick now....have to give it more pedal before it drops significantly. Still, anything over 75% pedal.and it drops down into the 40's quick. I'm at a loss. I don't know what else it could be here. If it were sucking air around the manifold some way, some how, could it cause pressure to drop?

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What size injector are you running? What problems where you having prior to cleaning it, other then the crap around the WIF sensor. I would also check the regulator area, and fuel standpipe area in the secondary fuel bowl, for any obvious concerns

155/30. No issues holdings pressure before the cleaning. Cleaned it because it hadn't been done in the 3 years I've owned the truck, and figured it possibly had never been done. I'm not seeing anything in the secondary fuel bowl, and running a RR, so the factory regulator is bypassed.

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Hmm, only other thing I could think is an inlet restriction. If your fuel conditioning module is full of crap, had to come from somewhere, ie plugged up pickup tube

Seems odd that it got plugged at the moment I cleaned the thing. Like I said, I had ZERO issues holding pressure before I cleaned it.


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Yeah, there's not a whole lot you can mess up on the hfcm though. 1 side gasket, and the filter o-ring itself, along with the fuel pump. As long as all the seals are in good shape and sealing properly, and the fuel pump itself is good, not sure what issues you are going to have with it.

Yep...like I said, this doesn't make sense. A new pump, fueling 155/30's shouldn't drop pressure. If whatever went wrong is unrelated to anything dealing with the HFCM, then this is the wildest coincidence ever for it to happen at exactly the same time.


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Anyone know if the oil filter cap and the fuel filter cap on the hfcm are the same cap? Wanted to rule out a cracked cap...and I have a spare oil filter cap.

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Yeah they are the same cap.

Ok, I'm back on this. I'm about ready to pull what little hair I have out. So far, I've done this....

Tried a new cap and O-ring....no change
New o-ring on upper filter cap....no change
Took a hand pump and lightly pushed air through the feed line, back to the tank....no change (trying to rule out restriction)
Pushed air up the feed line to the upper housing....no change (again, ruling out any restriction on the engine side)
----when I did this, I had the upper filter out, and the cap just threaded on a couple turns. Once I started pushing air, after just a bit I heard it bubbling in the tank. Only place it could get there was through the return, so it apparently was pushing air through the entire system.)
Lastly, replaced the HFCM with a used one...swapped on my new pump and a new filter cap with my used filter. Again, no change. Didn't expect much, but I was out of ideas, and willing to try anything. Those are Motorcraft filters. Don't see where a filter would cause this issue though.

I'm seriously at a loss now. Only thing left is my friggen regulator, which is only about 3mths old (Aeromotive). At idle, pressure is fluctuating from 63 to 60....needle constantly moving. Does the same at a cruise going down the road. Fluctuates 2-3psi. I have 2 gauges on my regulator with a T....the mechanical one and the sending unit for the electric one in cab. Mechanical one even fluctuates a little at idle. Not sure what could be at fault with the regulator that would cause this.


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I've been fooling with this all day. Swapped on my old cheap FPR, which did the same thing. Rules a bad regulator out. Figured what the hell....lets do a bubble test, just to be safe. Passed that with no bubbles at all. So it's not an injector leaking. With KOEO, as the pump runs it sounds like air bubbles passing through my regulator. (I've sort of thought maybe it's sucking air somewhere). Unhooked the feed line on engine side of HFCM, ran it into a clear jug and cut the key on. Fuel had air in it at first, then clears up until right before the pump shuts off, then gets bubbly again. So, figured I'd rule out anything in tank. Unhooked the feed line on the tank side, ran some hose from the HFCM into a jug of fuel, with the engine side feed still in my other clear jug. Basically bypassing the fuel tank all together. Key on, and it's bubbly through the entire pump on cycle. So, it's sucks air in the HFCM, for some damn reason. Like I said, this one is new to me, I never removed the manifold, so it shouldn't be an issue there. All I can think of is maybe the o-ring on the filter itself is nicked or something. Either that or the one on the pump itself. Gonna put a new filter in there and see what happens. If this whole ordeal is because of a filter o-ring I might lose what's left of my sanity!


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Ive seen that once on a truck. Tiny pinhole in the suction side from the tank to the pump. Id recommend replcing your supply lines. An aftermarket hfcm replacement such as an air dog or fass will replace the lines.

I bypassed the feed/supply line from the tank. It's sucking air internally in the hfcm

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Ok sorry i just re read your post. I got kinda confused there for a second:doh:. You could always still install a new pump to take care of it though but yeah if a filter fixes it it'll be a hell of a lot cheaper and easier...

That is a new pump. Has maybe 500 miles on it.


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I never swapped only the pump when I was at the dealer. If the pump was bad it got an HFCM. I've seen a few people have problems with just swapping the pump out.

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This issue didn't start with the pump change. It started with a HFCM cleaning. Pump change came after the issue arose.

And I've changed just the pump on 2 others, and had zero issues to this day.


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Anyone want a dually? I've never had an issue frustrate me this much. It just doesn't make sense. New filters, o-rings and no help. Actually seems to have gotten worse. You rev it up in park and pressure drops. Was doing that before though. At idle, my gauges fluctuate 2-5psi up and down constantly...again, did that since issue started.

What I don't understand is Everytime the pump cuts off, the system completely bleeds off pressure. You cut the key on, it slowly builds up to 55-60psi, pump cuts off, I immediately cycle the key, and it has to slowly start building pressure again from about 15psi. I know it drops when the pump cuts off, but it doesn't bleed that fast.

I unhooked the feed line engine side of HFCM, hooked up a piece of hose, and ran it into a clear jug. Cycled the pump on, and it's bubbly fuel the entire pump cycle. Hooked that line back up, and removed the feed side before the HFCM from the tank. Again, put hose there and ran it into that jug of fuel, basically bypassing the tank and supply line...again, took a minute to build pressure. Cranked the truck, and my gauges fluctuate just like before. For whatever reason, something is going on inside the HFCM that shouldn't be. Only thing I haven't checked is return lines, but do I even need to? What could be sucking air, or leaking pressure, or a return line that would cause this issue? Isn't the return just gravity flow?

Part of me wants to just bite the bullet and do a fuel system, but the missus ain't going for that right now. However, my only other idea is a new HFCM, which coincidentally, costs almost as much as a fuel system.

Anyone see something I'm overlooking? Why is pressure bleeding off so fast after the pump shuts off?


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