early vs late model fuel pumps
 

i noticed the late model trucks dont have the "inline" pump setup like the older trucks . . . after some homework i found that ~'89 was the year they stopped using the low press tank pumps and the high press inline pump.

well:
- which setup can flow more fuel?
- are the new-er in tank high pressure pumps a direct swap?
- can they be used in conjunction with the older factory in-line pump?

Personally I would keep the setup the way it came from the factory. ie if an '89 or older keep the in tank low pressure pumps as well as the high pressure frame rail pump. I see no reason to change. Always follow the 1/4 tank rule (never run the tank below 1/4 full as the fuel cools the pumps) This rule applies to all years. A lot of of people think that is BS, but I have logged hundreds of thousands of miles in Ford fuel injected vehicles with zero fuel pump problems.

Well I suppose I should have indicated that im exceeding the limits if the factory fueling capability, and that's why id swap pumps. Im toying with the options that aren't aftermarket. . Id never even remotely ponder swapping pumps or playing with a stock fuel system inside of its capable range. Pointless.

And actually...there's another way to look at it. Why keep it factory? Ford saw fit to change it because the new setup worked better. And also, by upgrading (if it's pretty easy), you lose one pump. That's one less pump to fail later on. Also the wiring that goes with it. So, yea, I think it's worthwhile to swap.

Well unfortunately newer is not always better. Companies are always looking fir ways to reduce cost per unit (per vehicle). The late model in-tank pumps are without a doubt cheaper and simpler than the old tri pump setup, so with that bein sad I wouldn't be surprised if the old setup is better. But, the late model pumps might just be a great way to make a more-than-adequate fuel setup when combined with the older inline pump.

Exactly. I've run walbro 255hp pumps wih the stock inline pump. Works real well. The frame pump free flow is quite impressive and won't be a restriction. It will compliment it just fine. If you worry it's wearing out, buy a Bosch 044 pump to put in its place along with the 255s you'll have enough fuel to power the space shuttle.

So what is the rating on those late model tank pumps?

I know newer isn't always better...in a lot of cases it's not. But I think in this case, cutting out that third pump, is definitely a plus...

I can't remember but it's like a 160-175 lph at 40psi. I'm probably wrong but they are decent pumps. Free flow is over 255 so you won't be trying to push fuel through it.
(I reread above)
The stock "low" pressure intank pumps flow like a bugger but just won't pressurize. I'm not sure what the rating but ford put the numbers on the side of most all the pumps I've replaced.

I think one I replaced was 70lph but I don't remember what it come out of

hmm, i guess ill have to rip into the tanks that came out of my donor truck and see if the pumps read anything out on the housings. im thinkin if the high press inline pump is what does all the work to pressurize the rail then receiving higher psi from one of the later in-tank pumps that will actually pressurize the rail on their own will be akin to slappin an aftermarket "in-line" pump so often associated with car builds and lazy folk (ive never been a fan of adding in-line pumps to "lift" a stock pump in a high performance app)

I can't remember where, but i've heard this to. I personally have never ran close to empty. My own little rule is, when I hit half mark, that's when I start looking around for the cheapest price, when I get it, I fill it right up.

I to, never had a problem with in tank pumps.

Ive heard the in tank pump works great in a carb application when you delete the frame rail pump, but i have no first hand knowledge of this. And none of this applies to your situation anyways so.... lol

The newer type are 125 LPH (33 GPH) @ 310 KPA (44 PSI).
The older in-tank pumps are the same pumps used by Ford before FI on the carbureted engines.
They just added the selector valve and high pressure pump when they went to FI.
I have used in-tank pumps out of a FI 1989 Ford on an older 1982 carbureted E350 RV with a 460 engine.

The photo below are fuel pumps out of a 1995 F150 with a 5.0L but the same pump are used on the 7.5L engine.
http://i54.photobucket.com/albums/g9...03489small.jpg
http://i54.photobucket.com/albums/g9...03491small.jpg

/

thanks for all the help. i certainly suspect ill have some lean issues caused by the fuel system. the tank pumps are original with damn near 300k miles on them, so once i get it up and running ill probably swap the pumps from my parts truck to remedy any lean issues. ill post up the results so others can benefit from cheap fuel system upgrade if (assuming its successful) they too suffer from a lack of fuel supply.