1997 f250 hd diesel fuel system
 

Could someone explain the 1997 hd diesel fuel supply system? Not the injectors but the tanks pumps and selector valves and all!

my issue #1 neither front or rear tank fuel gauge works. Rear tank will come up a little past 1/8th with full tank. Nothing on front tank. Ok no biggie as bed is going to come off to put a service body on it. Tank work should be easy then.

problem #2 shortly after selecting the rear tank the engine loses power and runs pretty rough. Zwitch to front tank and after a min it straightens up and runs good. To me clearly fuel starvation on rear tank. Engine does not die but lacks power!

ok so on the diesels is thier a boost pump in the tanks or on the engine only? Could i have a selector valve issue?

does anyone knkw where there is a diagram of this system? The 97 hd seems to be a lost child of the ford line. Still has the pre 97 body style and none of the books cover a 97 hd.

Well after more reasearch i see there is only a pump on the engine and a fuel selector valve to switch between tanks. I fivur with my syptoms it has to be a fuel selector valve. I also think my rear tank is filling when running on the front tank. This would also to me indicate to me selector valve.

This would probably get more attention over in the 7.3 forum.

The earlier DI 7.3s had the mechanical fuel pump in the valley of the engine. It's a dual, parallel tricky little setup. I want to say the later ones had an electric pump, wouldn't swear to that, maybe a mod, maybe I'm thinking 6.0. 7.3 never had pumps in the tanks like the gassers. A vacuum gauge on the suction side of the pump will tell you if you have problems in the tanks or valves. Google search for "coffee table books" or "bible" for the 7.3. Those books tell about the changes and have pretty pictures too. You can access them online.

The fuel pickup in the tank is sometimes called a tophat or something like that. They can fall off, rot, clog up, etc. Sounds like your rear tank problem. With the gauges and selector valve involved I would track down the electrics first and then look at contamination, corrosion, etc.

Read about HEUI and where the powerstroke label came from. The earlier diesels were IDI, then came HEUI and later ones were CRD.

The transfer switch 6 port controls which tank is being drawn from. and in the selector it also switches the sending unit from front to back. When the front tank is selected a plunger moves to open the front tank ports and makes a connection to the front sending unit Visversa to the rear tank, Sounds like a bad selector valve!!

I live very rural and sometimes my internet searching capabilities vary with weather, wind, sun spots and luck lol. I did manage to find a diagram last night that showed the switch in the valve to select as to which tank the gauge is reading. I have also kind of come tot he conclusion the best bet is the selector valve.

I called oreillys auto parts and they have a 6 port 5 wire valve for around $70. Do you know if this is a good valve or if it is a direct replacement valve?

https://www.oreillyauto.com/detail/b...r+valve+6+port

ok answered my own question lol abd answer is no. The ports are all different and wrong direction.

cheapest valve i can find is $280 on e-bay. Guess im nust bent over the barrel on rhat one lol!

Personally I would check to see if I was getting power to the selector switch before I replaced it but it is your time and money. Good luck.

i get what your saying but i would think that if it wasent getting power the valve would be stuck to where it can only operate on one tank. In my problem it operates fine on tbe front tank except it returns to the back tank. When you flip the switch it does swich off of the front tank but for some reason its not getting flow from the back tank. Not sure how its all wired and i wish i could find a wiring diagra. For those circuits. Im not saying its a bad idea. Just with partial funtionality i dont see it could have any functionality without power. Or thats how my mind works it out. I guess i could check it at the valve also. The plug is redily accesable. Its got 5 pins. Like i say i have not seen a wiring diagram but i have to figure that 3 are for the fuel gauge. One from each sender and one to the gauge. Rhe other two ha e to be for the motor to run the valve. Not sure how it does that with just two wires and the only thing i can think of how the pump and switch would work that way is if they were using the switch to reverse the polarity of the wires thus controlling the direction of the motor. I really need a diagram to be sure and my computer is running way to damn slow to search right now lol. Have to wait till i can hit the library.

Looks good. Check the sending units and the grounds too. That looks like a diagram out of an EVTM manual. Don't pass up a great deal on a manual.

The fuel pickup in the tank. Heard it called a showerhead and stuff like that:

https://www.strictlydiesel.com/p-271...up-screen.aspx

A common problem to be aware of.

good manuals are so hard to find!

It just suks you have to pull the tank to check that!

Had some time this morning to crawl under it and do some testing. I pulled the plug at the fuel transfer valve and tested for power and ground on the two wires the diagram shows. Just as i thought they both have 12v or continuity to ground with appropriate switch setting. Ok so checking continuity on the sendi g units to ground i get 38 ohms front tank and 68 ohms rear tank. This corosponds with what im getting as per gauge reading. Ok then when i ground out the gauge wire with 150 ohms of resistor in series to that circuit the gauge clibs up to just a hair past full. So by this I know the gauge and gauge circuit is good.

there does seem to be a fault with the sending units as both tanks are full. I think i saw somewhere that the sending unit and showerhead pick up unit are both in the same unit. Is this true? If so might explain my issues.

at this point im thinking there is a good chance the valve is ok. It might just be an issue with the showerhead pick ups and sending units. I am thinking i need to pull the box off and check all this out before i condemn the valve. I have to pull the box to put a service body on it so its reall no big deal and far esier for me to pull than dropping the tanks!

Holy crap! $250 for a sending unit. Thats just criminal and insane!