Hi all,
I have been reading up on the common 7.3 fuel system mods (hutch, harpoon, RR etc.) but I think in order to understand them better, I need a better understanding of the stock fuel system. Could anyone describe it, or better yet, provide a diagram?
Thanks

 

It's actually fairly simple. The pickup in the tank feeds the pump on the fuel rail. The lines between them have quick disconnects that leak under vacuum. The fuel pump feeds the fuel bowl in the valley of the engine. There the FPR and return line makes it's way back to the tank. There are also two feed to each of the head from the passenger side of the bowl, and drain on the rear of it (yellow handle). The pickup also contains screens that can get clogged up, and the return line actually feeds directly into the pickup. And there is a small duckbill aux pickup on the side of it to allow the system to suck fuel if the pick up foot gets clogged. That entire ***'y is removed when the Hutch is done, and the return line is extended away from the pickup. Lastly, the line between the pump & tank is replaced with a piece of hose with a filter of some type put in line there.

Hope that helps...

 

Thanks Joe, great post (reps). So there is only one fuel pump, the one on the frame rail under the driver's seat?

 

Correct. And the stock system (mod'ed, of course) is plenty for more HP than the stock block can handle. The Hutch/Harpoon & Reg Return/CCK is all I'd do (and all I have done) to mine.

 

Here's a diagram...

 

That's close, but missing the mixing chamber in the tank. The return line ties directly to it, which makes the aeration issue more problematic. The more air that gets sucked in and sent to the return, the more air is in turn sucked into the pump until eventually, I can imagine it running on foam. Not a very smart design...

 

I think you have to look at the reasoning of the ford engineers. Which is a bigger issue... Clogging the pick up and the truck is stranded? or The system gets some air in it?

I would say that the obvious best choice is the hutch w/ an pre pump filter. But I understand the logic behind the design.

Now I am not trying to be a d!ck or anything just saying that air in the system is better than dropping a tank on the side of the road.

 

The screens in the mixing chamber can STILL clog. That's one of the reasons we get rid of it, because if they clog, you'll still have to drop the tank. Air getting in there just adds to asinine design, because they followed that with a dead-head fuel feed from the bowl. And I don't think you're being a d!ck, just for the record. LOL

 

Cool stuff, guys. So, with this added info, why does #8 deadhead? I've seen CCTs where #8 scores much worse than all the others, and it is normal. What's the deal? I've read about it before, but never fully understood why, or why a cross-over would help. Also, why cross-over the high-pressure oil?

 

Injector #6 fires just before #8, and they're right next to each other. The theory is that #8 is shorted a little fuel, so they put in an AE that shoots in a little more fuel to make up for the difference. When you put in the CCK or RR, the fuel isn't dead-headed there, so you can put in a regular AD injector, if you wish. I was going to do that, but decided not to because I knew I was putting in a complete set of hybrids at some point (which I have since done). The RR or CCK also allows any air making it past the fuel bowl to be sent through the heads to the return line without necessarily going through your injectors. This makes it much easier to purge all the air from the system with a few cycles of the key. I know when I have my system open, I just cycle the key three times before I start the engine. Never had any problems with air in it.

The HPX is completely different. That is for connecting the high-pressure oil rails together, which evens out the pressures on the system allowing for a smoother, quieter engine.

 

Ahhhh, I see. Thanks all!

 

The mixing chamber was designed as a cold weather fuel gel prevention system, returning warmed fuel to the mixing chamber to keep warmer fuel flowing through the lines. It works well for that purpose, but returning air is an unfortunate side effect.

 

Here's the diagram for a second time and hopefully it'll stay around this time around...