Cleaned HFCM, now losing FP

[mandkole]

Not sure why Im so interested in this issue since I dont have a 6.0, but its kinda fun...lol

Ok, stay with me on this thought. During this koeo flow test, are you (or can you) return fuel from the engine? If so, at some point seems possible you will pull air. Since the dtrm is a thermostat (and at a cold temp of allowing fuel to loop back to the supply) is it allowing return fuel to be reintroduced to the supply are you introducing air there due to running the line out? Does your return connector possibly leak and its pulling air by the DTRM?

If no other connectors leak, its time for the other unit out of the 03. Just warn your dad that you could jack his truck up also...oke:

 

[6speedsd]

With the line ran out during the test, no fuel is being pushed to the engine, so none is pulled through the return.

I could understand what you are saying about the DTRM and cold temp, but after the truck has been ran a while, shouldn't it be taken out of the equation, since fuel is just returning to the tank and bypassing the DTRM?

I actually ran the same test last week, with the return ports on the HFCM looped together...got the same result.

Isn't the return on this thing basically pressure? It's not sucking fuel back to the hfcm/tank, but being pushed back by the pump at the end of that looped system (if that makes sense). If the return connectors were not sealing, they should be leaking fuel, not sucking air.....correct?

(Hopefully I'm not trying to over think all this)


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[mandkole]

as I understand the dtrm, it will be in loop until the motor is under heavy load and the fuel is heated to the point it needs to keep going back to the tank. The return is normally under some positive pressure, but your system is different than a 7.3 so I wasn't sure. Just thinking about all possible ways it could be pulling air

 

[6speedsd]

It's all good. That's why I posted here...to get other opinions, and other brains smarter than mine thinking, as I've obviously exhausted all my ideas thus far.



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[mandkole]

hey, did ya get that issue dialed in? did the ol mans assembly fix it?

 

[6speedsd]

Haven't even tried sadly. Been too busy. Actually going to try the same test again with my unit with a piece of clear hose on the supply side from the tank so I can watch for air pre-hfcm. Just want to confirm that it isn't a tank/supply line issue before the hfcm before I proceed.

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[6speedsd]

Finally got to fool with it again. Clear hose on the supply side of the hfcm, pump running, and it's definitely sucking air from the tank or the line leading up to the tank. Chitty part is I have a full tank of fuel!

So with all that said, what is actually replaceable in the tank? I'm assuming it's an issue with the pickup tube, but what can be replaced in there separately? Anything, or do you have to replace everything as one piece?

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[6.0 Tech]

You can replace the sock separate from the sending you nlunit, otherwise, it is a full sending unit. I have seen where the sock has fallen off and parts plugged the pickup. But i have also seen once where there was a pinhole in the line that i could not see. You should remove the suction line from the tank and run it into your own jug of fuel if there is no air, its in the tank. You can get at the line with the tank still installed. Its kind of a pita on the ground but easier than dropping a full tank on the ground.

 

[sootie]

its way easier to pull the bed off than drop a full tank of fuel...

 

[6speedsd]

Oh I'll drain the tank someway before I fool with a full tank. Don't really have a way to lift the bed other than a floor jack and some blocks.

Starting to sound like a good time to run that sump I've been putting off for a year. Any downside to running a sump with the stock pump?


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[mandkole]

Ok, so you had no fuel pressure or air issues before servicing the Hfcm? If no, seems all too strange that the pre pump plumbing now has leaks. Hate to see you suddenly take the tank apart

 

[6speedsd]

Yeah bud I know. Like I said, this all is one hell of a coincidence. It just makes no sense how it all came to be.

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[6speedsd]

I want to just throw a new hfcm/pump on it so bad, but that's $300 I'd rather keep in my pocket until I know for sure that's my problem.

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[mandkole]

I hope youre right and best of luck to ya... Cant you get a prepump hose assembly for $20-30?

Id be doing everything possible to avoid that tank drop.

 

[6.0 Tech]

Have you tried throwing your dads pump on it yet? That would rule out the pump once and for all. Also try running the suction line at the tank'm into your own jug like you did right off the pump. That would rule out either your sender or suction lines. You dont have to drop the tank for that.

 

[6speedsd]

I hope youre right and best of luck to ya... Cant you get a prepump hose assembly for $20-30?



Id be doing everything possible to avoid that tank drop.

$20-30.....hahahaha. Ford only sells it as a set... Both fuel lines and the brake line....tank to pump, something like $365. I can build my own lines for 1/3 of that.

Have you tried throwing your dads pump on it yet? That would rule out the pump once and for all. Also try running the suction line at the tank'm into your own jug like you did right off the pump. That would rule out either your sender or suction lines. You dont have to drop the tank for that.

Not yet. Something about taking working parts off a working truck bugs me. Lol. I need to though, like you said just to rule it out. How do you get to the suction line without dropping the tank or lifting the bed? Doesn't seem like there is enough room to get your hand up there.


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[mandkole]

I thought that Dorman sold a nylon replacement fuel line, but not for 6.0.

How did you hook up the clear line to the existing line to make you think it was pulling air?

 

[6.0 Tech]

On the ground you will probably have to drop the driveshaft. But you can get your hand in there to disconnect it. I did it when i put my air dog in since i havent yet bought a sump. Ive got pretty thick arms too so there is a decent amount of room. Id guess 4-5 inches probably.

 

[6speedsd]

I thought that Dorman sold a nylon replacement fuel line, but not for 6.0.



How did you hook up the clear line to the existing line to make you think it was pulling air?

I already ditched the factory supply line with the quick connect, back to the hard line anyways. Have fuel line ran from each, and double clamped at either end. Just pulled that line off and replaced it with the clear long enough to cycle the pump 6-7 times.

On the ground you will probably have to drop the driveshaft. But you can get your hand in there to disconnect it. I did it when i put my air dog in since i havent yet bought a sump. Ive got pretty thick arms too so there is a decent amount of room. Id guess 4-5 inches probably.

Good deal, I'll give it a try. Thanks.


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[6.0 Tech]

No worries man. Give me a call if you need any more help too.