hey everyone my buddy has a 96 f250 5.8.. the truck seems to have farting fits randomly while driving..also the gas seems to move from his rear tank to front tank, over filling the front tank then pissing out of the filler neck... he says the gas always moves from rear tank to front tank, i don't know if this is true for not... any ideas would be great , i've put more hours into this truck then my own.

 

He has a bad front FDM high pressure check valve or return shuttle valve in the front tank.

 

thanx for the reply.. ill send the info on and he can learn how to turn a wrench haha

 

Has there been a tech article in the past on this fuel system. If not some good tech info would be great as I also have a transfer problem and haven't had much luck finding any info on the systems on 92 and up 7.5 F-350's. Any help is greatly appreciated, thank you

 

What do you want to know about it?

Image of the fuel system:


Here is an image of the FDM:


FPR:


Fuel Pump:

 

Thanks for the illustration, my question is dealing with the front tank adding full when running from the rear tank. Does the entire front tank module need to be replaced to repair a transfer issue or just the regulator or shuttle valve. It's probably easier and more cost effective to replace the unit. Thanks for the helping hand.

 

ya more info would be awesome as this is not my truck..where is the fdm and shuttle valve located?

 

Looking at the diagram of the FDM above the shuttle valve is inside of it on the return fuel line from the FPR.
The FDM is located inside the tank.
The Fuel Delivery Module (FDM) is called the Fuel Delivery Assembly in the diagram but they are the same item.

The electric fuel delivery system used on the 4.9L, 5.0L, 5.8L and 7.5L multiport fuel injection (MFI) engines (6007) consists of a fuel delivery module (FDM) and sending unit. The fuel delivery module includes a high-pressure fuel pump (9350), venturi jet pump, supply check valve, and a shuttle selector valve located internally to a reservoir mounted from the fuel tank sender flange.

The following provides a brief description and function of each of the fuel delivery module internal components.

The high-pressure fuel pump is located inside the module.

The shuttle selector valve opens the return line to the tank and the return flow is directed to the appropriate tank on vehicles equipped with dual tanks.

The supply check valve, which is normally closed, opens when the outlet pressure from the energized pump exceeds the opposing check valve spring force. When the pump is de-energized (i.e., engine is shut off), the supply check valve closes to maintain pump prime and fuel supply line pressure.

A portion of the high-pressure flow from the fuel pump is diverted to operate the venturi jet pump. The venturi pump draws fuel from the fuel tank (9002) into the fuel delivery module reservoir to augment the engine return flow. This process ensures an adequate fuel supply to the fuel pump during extreme vehicle maneuvers and steep vehicle altitudes with low-tank fill levels.

The inlet of the venturi pump has a nylon filter on it to prevent dirt and other particulate matter from entering the system. Water in the fuel tank can pass through the filter without restriction.

The in-tank mounted fuel delivery module containing the fuel pump is capable of supplying 105 liters (27.7 gallons) of fuel per hour at a working pressure of 270.0 kPa (39 psi) for the 5.0L, 5.8L and 7.5L MFI engines. The fuel delivery module can supply 90 liters (23.7 gallons) per hour at 380 kPa (55 psi) for the 4.9L MFI engine. The fuel pump has an internal pressure relief valve to provide over-pressure protection in the event the fuel flow becomes restricted. Over-pressure is restricted to 850 kPa (123 psi) and reduced fuel flow will result. The system pressure is controlled by a fuel pressure regulator (9C968) on the engine.

I hope this helps.

 

Yes the entire front tank module need to be replaced.







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thanx for all the great info

 

I have the same problem.

I don't need two tanks. Is there a way to bypass around the front tank?