Ok I did a search,trere were about a zillion threads. So if someone can help me I would apriciat it.So here is the problem.The rear tank does not work,flip the switch gauge goes to E mile or so down the road truck burns whats in the lines and does not pump. rear tank is full.With the truck turned off and key on I can flip the switch and hear a relay kicking in so I do not think it is the swich, but I am new to this. so is this a common problem?any help would be great thank you

 

Try this: with the tank selector switch on the front tank, turn the ignition on (don't start the truck) and the driver's door open. You should hear a whirr/whine/hum that last for about two seconds or so. Now, turn the ignition off, flip the switch and do the ignition thing again. If there's no whirr like the front tank, it's your switch, relay or pump. Troubleshooting would be to start probing for voltages and such, but there's a good chance it's the pump. It sounds like the switch and relay are working from what you said. A lot of guys here have said it's much easier (with help from a few large friends) to pull the bed and do the pump from the top than to drop the tank to swap it out.

Jason

 

This may help.

 

thanks guys,I amgoing to dive into this this weekend

 

Subford did they use the same setup for the diesels?

 

i know on my truck i have three fuel pump-frame,front intank, and rear intank...it is hard to tell if the front or rear intank pumps are working by yourself because the pump on the frame is right under the front door

 

FOR Diesel Engines ONLY

Popa Tim
NO, they used something very different.
The fuel pump (9350) is bolted to the top of the cylinder block.
The fuel pump is mechanically operated by an eccentric cam located on the camshaft. The pump actuator rides against the eccentric, providing the diaphragm up-and-down pumping motion.

Fuel Selector Valve
The six-port diesel fuel valve is powered by a small electric motor which opens and closes the valve ports. The supply and return ports for either tank open and close simultaneously. The valve is shifted to the front mode (that is, the front supply and return ports open to the engine supply and engine return port respectively) by applying a positive 12 volts to terminal 2 and ground to terminal 1. When the valve reaches the front mode position, an internal switch opens the circuit and stops the motor. Returning the valve to the rear mode is accomplished by reversing power: positive 12 volts to terminal 1 and ground to terminal 2. Terminals 3 and 5 connect to the front and rear fuel tank senders respectively, and terminal 4 feeds the fuel gauge. In the front tank mode, an internal switch connects terminal 3 to terminal 4, thus supplying the front tank sender signal to the fuel gauge. Terminals 4 and 5 are connected in the rear tank mode. Therefore, a change in the fuel gauge reading (assuming at least 1/4 tank fuel level difference), means that the valve has shifted.

 

someday

Yes on your 1989 F350 you had three Fuel Pumps, an High Pressure on the frame, one in each tank and two ran at the same time.

But oldyj has a 1995 and it has only has two, one in each tank and they do not run at the same time.